How to diagnose a mystery coolant leak in a Chev/GM truck

[@squidhound00001]

I’m having the same issue with my 2000 GMC. No trace of a leak anywhere that I’ve found so far. I’m going to go right to this spot and see if that’s the culprit. Thank you so much for posting this !!

[@ElleBrOw]

Hey did you check it out ? I’m gonna share this video with my mechanic.

[@squidhound00001]

@@ElleBrOw yep , we’ll I think it’s the main problem anyways. it was the water pump intermittently losing coolant out the weep hole. Just strange cuz it never left a puddle or trace. I caught it early. I’m hanging a new one on today.

[@rusco321]

Coolant is routed through the throttle body to prevent freezing of the throttle blade in cold climates.

[@spelunkerd]

Good point! I don't see an internal pathway around the throttle body but it wouldn't need much, given how close it is to the throttle butterfly.

[@billk5727]

rusco321 is right. Prevents ice formation at closed throttle at the butterfly plate. Old carbureter cars were famous for this problem even with heated intake air and or heated throttle bodies. More so when the temp is below 40 degrees F. with high humidity.

[@placidbeach]

Don't know if you guys will see this after so many years and also I'm sure this is totally unrelated, but small Cessnas and none fuel injected gasoline airplanes have a carb Heat lever to pull when you Throttle Down such as when coming in for landing, and you do it summer winter no matter when.

[@mdwdirect]

It's nice to find an easy one occasionally isn't it? Your explanations are great. You don't skip ANY steps and even give us the nut driver size. Thanks!

[@spelunkerd]

Yeah, I was due for an easy one, ha ha. Thank you for the kind words! On the contrary, when I make a video I usually wish I had worded some clips a little differently. At some point, you have to finish and move on to the next one. People are usually kind enough to overlook imperfections.

[@spelunkerd]

@@TaraConti Sounds like two fun challenges, likely unrelated. I made a playlist of cooling system problems you might find helpful. These days a leaking radiator would be high on the list for an obvious coolant leak. In any case, with an obvious puddle it should be easy to find the source. Good luck!

[@dominicgreen524]

Have me a 1996 Chevy c1500 centurion- had the same issue and felt like I was going crazy. Thank you so much sir! My Frankie will be fixed up in no time now. Don’t ever stop posting videos,you're one of the few that gets shit done. Thank you !

[@chuck1607]

I'm having the same issue with my LQ4 (2003 H2 Hummer). It's leaking from the same general area. Thank you for taking the time to put this video together. I will take a peak at mine and hopefully I have the same issue. Cheers!

[@carlsanch3ify]

Oh man, I almost bought an entire water pump system. Mine does leak and leaves a puddle and I just could not find the darn leak. I will check that later in the week. I went to Walmart and they told me I have an oil leak yet I have no oil on my driveway. This video is a major help.

[@justinsander7654]

I have been searching for the leak in my 05 silverado for 3 years been to the shop half a dozen times you have given me a good place to investigate thank you.

[@spelunkerd]

In addition to leak at that hose, this generation of the Vortec engine had a problem with porosity of their aluminum cylinder heads, leading to some developing tiny leaks through the head into the oil. I'm not sure about the 05, you might have a look at the cylinder head id number and the oil fill cap. Leaking there can cause a brown pudding forming on the inner side of the oil fill cap, although sometimes you can get a little pudding even in a normal car. Good luck!

[@ESBEAUTII]

Mine leaked into my engine oil and I ended up needling a new engine

[@davidkeddy7717]

@@spelunkerd But his leak was external, he could see a puddle on his driveway. His leak was not internal, where as an internal leak, you would not see a puddle on the driveway

[@reggiesanders1229]

Great video! Thank you for your time on finding that problem. I'm sure you saved a lot of people from wondering where that mysterious leak was coming from. Appreciate this video. Thank you!

[@ManicMechanic007]

Determination and patience paid off. A pressure tester sure helps when looking for coolant system leaks. Well done.

[@JUSDAR]

Man i have a 2001 and I couldn't find where that leak was coming from and now you open my eyes I replaced the top hose even took out the thermostat I bought today a water heater but the leak is not near the water pump so it has to be your find thank u for your find....that made my day

[@dbernstein7901]

Good catch, nice, informative. The 5.3L engine was used throughout the GM models but never saw a coolant connection being used on the throttle body!

[@billybobbarker3175]

NICE! Happy I found this. I have a mystery leak on a 2000 gmc with the 5.3. I recently had the throttle body off for cleaning, and at the time was cursing those small hoses. Today am under the truck fixing of the stuff and notice a small/slight coolant leak dripping from the front of the engine. I know exactly where I am going to look tomorrow. 👍

[@spelunkerd]

If you can't see leakage with engine running where mine was leaking, you'll need to get a closer look from underneath. Pay close attention to the radiator, which commonly leaks where plastic meets the aluminum heat exchanger. To inspect properly underneath you'll want jack stands (not just a jack). You'll need to remove the skid plate that is bolted on and plastic covers. Then when engine is not running crawl underneath and find the water pump. A common source of leak is the weep hole from the water pump. I did a whole series of videos on your engine, and I have a playlist of cooling system problems on my channel you might find useful. Many demonstrations were done on your engine. Good luck!

[@billybobbarker3175]

Thanks. It looks like it is leaking from the water pump to block gasket, on drivers side near the power steering pump. So the dilemma I have now is do I go with a whole new pump or just replace the gaskets. I will look for your other content on this one. Great quality content videos by the way. Very professional. 👍

[@spelunkerd]

@@billybobbarker3175 As I recall, I did a two part video set of this exact many repair years ago, it was about 2013. Content delivery is a little slow in those old videos but the information is there. Back in about 2020 I had the same leakage where you describe and I did the repair again off camera. It's been fine ever since, I drove it yesterday.

[@spelunkerd]

Oh, one more thing. When I first did this water pump in 2013 I came down heavily on the side of replacing the pump at the same time, which is a work pattern followed by most pros. Given the poor quality of the last remanufactured pump I got from NAPA in about 2020, I've been rethinking that bias. Even the weep hole on that reman pump was covered over with paint. At that time I got better gaskets separately so I didn't have to use the thin paper gaskets that came with the pump. So, it might be an idea to replace only the gaskets, they were easily available at that time. Pros don't do that because they don't want to warranty the labor, but in amateur work flow the cost of labor isn't very high, ha ha.

[@billybobbarker3175]

@@spelunkerd Exactly my thoughts. I picked up a pressure cap for testing. Will try that in an hour or two, and go from there. I hope/plan on just the gaskets and resealing the backing plate of the pump, assuming that is the leak area. Even though it is old and probably original, I have no bias or want to replace the pump if it is not showing anything from the weep hole. Circulation is good, heater blows hot, and pump turns smoothly. Just a seepage and small daily drip to find and fix. The truck has 238,000 Km. Thanks a lot for the thoughts and encouragement.

[@bkupkee]

Great post!!, Exactly as what's been said earlier about the freezing prevention. My old BMW's ('80's E30 series) all have the same thing!

[@SuperMarioDiagnostics]

Very cool find Dave! Leaks are one of the few things in life you start from the top😎

[@GaryKelleyGrownupRadioSanDiego]

I like your kind style. Thank you!

[@robertoleeva985]

Dude you rock !! I wish some of my teachers were as good as you.

[@AlecBig]

I looked right where yours was dripping and was able to confirm that's where my was leaking from thank you very much for this very helpful 👍

[@olenaerhardt7725]

I need to find a small coolant leak in 2003 Chevy Cavalier. It is dripping from the right side below. Thank you for pointing the possible locations of the leak, like by the throttle body hoses, and how to use the Coolant Pressure Tester.

[@BrokenRRT]

Check your heater core connections. When you say right side I’m assuming you mean passenger side. That’s where your heater core connections is located. Also check the floor inside on passenger side to see if it’s the heater core itself leaking.

[@Blackberry7399]

Thanks for the video.. My 2000 Silverado is always in need of fluid but thankfully Never ran hot.. I do hope this why I keep loosing fluid and seeing no leaks in my oil or anywhere..Thanks a bunch for this information👍👍

[@spelunkerd]

Thanks for the sub, man!

[@damienlopez6487]

Leonard was this your problem after all? My 06 silverado is doing the same. Never goes hot and I'm constantly filling up on coolant but never spotted a leak

[@jorgegil3770]

Thanks for this video my dad yukon has the coolant smell but the main hoses are dry I will be looking at these hoses today thanks

[@MotherOfCivilization317]

same here today! Any updates on what you found?

[@whothecapfits]

Thanks for your helpful videos, sir. One helped me replace the AC compressor idler clutch pulley on my Dodge truck, when bearing gave out. I also dealt with a small coolant loss on said truck, losing about a cup full every few days. Pressure testing didn't reveal anything, but I used one of those block testers with the blue dye and it detected exhaust gases in the coolant. So now I was dealing with a tiny head gasket leak. This was further confirmed when I scoped the cylinders and found a tiny bit of coolant in cylinder #5 (4.7L V8 engine). I only noticed it because I was leaning heavily on the truck which shook it, and I saw the liquid move on top of the piston, on the very grainy video. Well, the truck wasn't worth much and I was determined to do everything to not to have to pull the head gasket. Against my normal judgement, I used one of those block seal products, but used it very judiciously in a targeted manner, disconnecting the heater core during use and flushing out the radiator before it dried. Supposedly the stuff turns to glass and melted copper flakes as it encounters leakage in extremely hot places. I drove with it for many miles as initial application using the instructions did not work for such a tiny leak. Anyway, that was over 5 years ago and the truck now has 300,000 miles on it with no further loss. I later learned that Dodge coolant has silicates to prevent such leaks but I was using silicate free, so that might have contributed. Thanks again for your videos.

[@spelunkerd]

Thanks for the followup, you made my day!

[@stuzman52]

Great video Dave and I can see how that tiny leak would be hard to find. I suspect that the coolant passing through the throttle body is to help the fuel vaporize during the winter months. Good work!

[@spelunkerd]

I love reading discussion threads like this, they usually add something that brings color to the video. Thanks for making it worth reading!

[@BigRichardsGentlemensClub]

I doubt it since that engine is fuel injected.

[@kennethstabler1217]

I’m having that same problem thank you for this video I never knew about those hoses.

[@93vanhalen]

And I believe the hose on the right of the throttle body is the one that goes to the steam crossover lines that run under the intake manifold.

[@charleshayes4104]

Thankyou that is exactly what my problem was you hit it on the head and saved me headaches

[@66crush9]

love your problems, cause they match my problems and the coolant checker is like mine as well, turns out my seep holes are leaking on my water pump ever so slightly, could not find it otherwise.. Slant coolant checker would have cost us way more , great diagnostic tool here.. and awesome video as always...

[@spelunkerd]

Thanks, man! The one thing my kit is missing is a cap tester, though testing the low pressure valve in the cap can be done easily with no tools. Most cap problems are at the seal, easy to inspect, anyway. When I look back, cooling system problems and battery problems are the core of DIY auto repair. If you understand those, you can cope with the vast majority of auto repair problems.

[@vicreyes6404]

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[@66crush9]

@@spelunkerd i ended up having to make my own cap inspector for this kit, still great price and offerings overall..

[@terryrhyne9112]

I have a 03 gmc truck and you explained exactly my problem. It's driving me crazy trying to find it. I'm going to check it tomorrow and I bet that's my problem Thanks Alot.

[@toddforslund3571]

Any update?

[@wgwspoon929]

Great video information. I've got a 2004 Yukon Denali an I've been having to add coolant a lil more than normal. You mentioned burping the system which was very informative. I'm gonna try this tomorrow for sure. Thanks

[@backyardgrillmaster2910]

Thank you for your time

[@ozielpulido9545]

Very good video.. I get a strong smell of antifreeze on my 06 tahoe after engine has been running for a while. Although it doesn’t overheat I will be checking that next..

[@spelunkerd]

If you can smell it in the cab, check the floor mats, it is probably a leaking heater core. The one other thing that can cause wet floor mats in some vehicles is the drain for the AC evaporator, which can get plugged with dirt and cause overflow, but that is just water, not coolant. Heater core removal is a pain because of all the plastic you need to remove to get at the coil. Good luck!

[@ozielpulido9545]

Thanks for your advise.. I will be checking the hose under the throttle body next.. since the passenger floor board is not wet and you can only smell the antifreeze when you descend the vehicle after it has being running for quite some time.. thanks

[@biggmike419]

Thanks for the info, now I have a place to start looking 👍🏼

[@elcheapo5302]

Great vid, as always. Glad it was a no-cost fix!

[@spelunkerd]

Yeah, always the best kind. Without the pressure tester to identify where the water was coming from, one might have been led to the misleading conclusion that the water pump gasket was bad. I wonder how many water pumps are replaced on these vehicles when the real culprit is a leaking hose above.

[@elcheapo5302]

Agreed! I need to get one of those. I heard you say it was an Astro, do you have the model number? Thank you!

[@spelunkerd]

I bought it about a decade ago, Astro 7858. Less expensive alternatives are out there, especially if you only need it for one vehicle. Also I believe some parts stores will loan equipment. Stant offer the core device on Amazon for much cheaper, then you buy the exact adapter for your vehicle separately. And I'm sure Harbor freight will offer something similar. I maintain a small fleet of vehicles so I wanted a kit that works for several models. The other option is to disconnect a hose in the system, then use rubber corks to jury rig an adapter to pressure test from the hose. Of course there is also the option to just run the vehicle to pressurize with the water pump, then carefully inspect. In that case you've got to avoid spinning belts and hot coolant that will boil over when you start the repair phase. I invest in tools with money saved from doing this myself, so in the end the main benefit of home repair is not financial. Insight gained from learning how these systems work is priceless.

[@kayeninetwo3585]

This guy is very good. Just discovered this channel and subscribed.

[@Jonnydeerhunter]

Very interesting. Thank you for sharing

[@ozzstars_cars]

Good find. Pressure testing on a cold engine makes things much easier.

[@tomreyes4908]

Thanks for posting. My truck seems to have the same issue. I checked and the block looks clean so I'm sure that's the problem.

[@PhillyChevy215]

I think you may have helped me find my mystery leak. Thank you so much.

[@PhillyChevy215]

It wasn't where my leak was, but it pointed me in the right direction. Either way it helped.

[@christianfloresjr5097]

Where was your leak? I’m currently trying to find mine

[@andrejohnson505]

Thanks! I have been fighting this leak for over a year.

[@sanhsands6132]

pretty awesome. And yes Throttle body is not even mention in the diagnostic. it's always the intake manifold.

[@spelunkerd]

I did a little research on that. The LS engine series had a coolant air bypass system that was designed to clear air pockets from all four corners of the engine waterjacket and send them back to the radiator and coolant reservoir. It was added to the design to prevent localized overheating. It also makes burping air from the system easy. In my engine you can see ~1/4" steel coolant pipes above the valley between the heads and below the intake manofold on my LM7 variant, and on other engines of this vintage. Those tubes merge together into one hose that goes to the throttle body, so that any ice in the throttle body would quickly melt. From there coolant is sent along the tubing that was leaking in this video, to arrive at a midpoint of the radiator on the right side. When Chev decided to add their notorious displacement on demand system, they deleted those pipes. Some guys modify those pipes to use braided hose, you can buy specialty tubing kits to do that.

[@theLastHuff]

God is good ..randomly found this video as I was pressure testing my 2002 Silverado and my leak was on the right hose under intake manifold

[@Corvette2]

Great info; thanks.

[@Pena.2]

Awesome, very observant

[@chrisheffernan6600]

Great find

[@Akhazmat907]

I have the same issue on this 99 suburban, just replaced water pump, thermostat and housing, radiator and upper and lower hoses. Left in garage for 3 days with cardboard under the suburban. I am gonna check this now. Thanks

[@christianfloresjr5097]

Did you figure it out??

[@Theo33311]

I thought it was the damn head gasket until I saw this video. I’ll be checking it tonight Mahalo.

[@genebenda]

Thanks! I’ve been wondering about my leak for years. It’s ever so slight if a leak but enough to make you or the wife worry. Same thing, no evidence of leaking anywhere but a slight smell of the coolant fluid was a give away. Seems the video was proof of where my leak was. Again thanks so much!

[@spelunkerd]

Common leaks come from the water pump seal or weep hole, hoses, sometimes the radiator or heater core, rarely a head gasket. This LM7 5.3 engine also occasionally had a notoriously slow leak coming from porosity of the head itself. Hopefully your solution will be more simple, good luck!

[@genebenda]

@@spelunkerd Even more helpful information. Again appreciate it!!

[@dannewton5363]

I'm dealing with this problem now, I bought a hose barb connector and bypassed my throttle body all together, good video sir👍

[@ColonelEMHouse]

Great job man

[@angelaracino6236]

My friend the hot coolant flows through the throttle body to prevent icing due to the temperature drop from the Venturi, Bernoulli’s principle states that when you move a mass of air or a fluid through a Venturi two things need to happen number one the temperature must drop number to the pressure also drops

[@spelunkerd]

Excellent point! It is so nice to find your remark, one that inspires deeper thought.

[@muhammadsaeed5517]

well done.

[@andrewgetchell2643]

I will check this out on my 5.3!

[@rogerw2101]

Hi I'm Roger the Farmer from Grantsburg Wisconsin ! I just found this in my feeds and have a 2000 Tahoe that I picked up from a kid who had it for about a month and smoked a Deer with it . It took the Grill ,lights , condenser, Radiator, coolers , fan , the whole front all most . I got it from him for 400.00 Buck's ! Bucks ! Lol Any way got all the parts for about 300.Bucks put all together and has been on the road about 6 month s and I started to drop COOLANT . I do have dash issues with the lights blinking on and off and Service 4wd light on all the time . And one I can't figure out . When I turn on the key it's always in 4hi . I have to push it to Auto 4wd then to 2hi with the transmission in neutral and push the button s a couple of times and then it will go to 2hi and the indicator light goes out and it's in 2hi . As soon as I turn the key off it defaults back to 4hi and I have to do it all over again every time the key is TURNED off ? Help I don't get it. I'm a Allis Chalmers Tractor guy not a GM Tech support guy ! Lol . I'm going to check out my hoses about the coolant and see if that's the case I have or they said it might be a cracked head too . I hope not. Thanks I hope you get this email

[@spelunkerd]

The transfer case switch that controls the FWD in these vehicles can go bad, which could cause what you describe. Also with all the front end damage you might have a look at the shift motor on the front axle, responsible for locking the two front hubs together. It is electrically controlled, you want to be sure those wires are intact. I'd check the fluids in both the front axle and also the transfer case. You may get more info from a high end scan tool. The transfer case in these vehicles has three VR speed sensors that help the transfer case do its thing, and if one goes bad it may interfere with shift control. I did a couple of videos of that problem in this vehicle. I also did a series of videos showing repairs of this Suburban over the years, including a few showing how to investigate a slow coolant leak. These vehicles were prone to a couple of things. The NVG246 transfer case was vulnerable to 'pump rub' causing catastrophic oil leaks, and also the cylinder heads were prone to porosity that sometimes caused a slow coolant leak. Neither of those happened to mine, yet.

[@ylemoine1]

Love the systematic approach you take. Obviously starting with the right tools and a clear understanding of engine cooling helps. Would love to see a similar vid about finding / repairing a refrigerant leak in a marine bar freezer. Most specifically a NovaCool F1900, but any bar fridge / freezer with 134a refrigerant in it should be roughly the same process I would think.

[@spelunkerd]

There are some very good videos on 12V A/C systems here on KZbin. For an excellent A/C review, search the RatchetsandWrenches channel, he's a good teacher. It took me a while to find the adjustment dial for the fridge cooler on our boat, it is hidden in a very dark corner of the pantry cabinet. I was sure glad to find it before asking my brother, an AC tech, to help me out. He would never have let me live that one down, (grin).

[@RG-wy1ol]

Thanks for making this video very HELPFUL 👍🏽👍🏽.

[@ComicAddicts]

This was a great video and very helpful

[@BBQandStreetCars]

Super helpful. I'm gonna check there first because after watching this I think mine is the same. Just got the sub button so I don't miss any more helpful videos. 👍👍

[@spelunkerd]

Thanks, nice to meet you. Dave

[@TexasPLNR]

I wonder if a spring clamp might be a better choice. Perhaps hose deterioration allowed worm gear clamp to lose pre-load. good video.

[@spelunkerd]

Yes, now that you mention it, I agree that spring clamps seem to do a better job for these small diameter tubes. I find the spiral threaded clamps on small tubes tend to dislocate and not give as much tension as I would like. Also this tubing is plenty strong and it doesn't kink but it is not very flexible. The next time I visit the parts store I'm going to pick up a few some smaller diameter spring clamps.

[@zx8401ztv]

Well that was a sneaky leak, very hard to detect without your pump up tool. You have some rubbish vehicles, they are always breaking down LOL :-D :-D Joking.

[@cesarrenteria914]

Great job!

[@toddgardner1086]

Hi, I have a 2016 chevy silverado 1500. I have a slow "mystery" coolant leak that takes about 2-3 days after I've refilled the coolant for it to start overheating. I can't really tell where the leak is coming from with all the emissions crap covering everything. It is wet all along the bottom part of the radiator and a very slow 1 drop every 5 min off the framing behind the headlights. I dont see wetness anywhere else. Radiator leak? things I should check first? Loved this video. I'm gonna start watching your other videos right now lol. oh miliage...130,000

[@spelunkerd]

Take off the plastic covers underneath and find out where that leak is coming from. Lots easier if it isn't raining outside, ha ha. The most common cause of a leak at the bottom of the rad itself is the radiator, which commonly leaks from the two plastic end caps, one on each side. Other places to look for are hose connections, the weep hole of the water pump, and various connections including the drain spigot at the bottom of some radiators. If the rad is leaking, simply replace it, nobody fixes those any more. Keep the reservoir full and don't delay repair.

[@viivcreations9161]

mine was a faulty leaking water pump seal. it only leaked when driving under pressure

[@nickwilson1476]

Hi Dave....another great video. Honda runs coolant through the throttle bodies to try and eliminate icing of the butterfly valve in cold weather.......I suspect Chevy is doing the same thing here.

[@spelunkerd]

Excellent thought, Nick, others said the same. Terry suggested it is to help fuel vaporize fuel in the winter, which is a variant on the same theme. People don't remember how difficult it was to start carbureted vehicles in the winter a generation ago. It was always a question as to whether one would get to work on time. Thanks for making this thread worth reading!

[@condor5635]

Not only the butterfly valve but maybe freezing in the throttle due to the Venturi effect I believe. Great video have to keep this in mind for my similiar 03 Suburban. Clean those leaves out of the hood! My pet peeve! 😁 thanks for video!

[@nowthatsfunny1]

Hello nice video. I assume that is a v8. My v6 is losing water but i dont think it has this hose. I imagine it is the head gasket I add coolant every month.

[@spelunkerd]

This vintage of truck is also prone to porosity of the metal used to cast the heads. The casting number on the head will help decide how likely porosity is. My casting number is 706, easily seen on either side by wiping grease off the top of the head (front on passenger side, rear on drivers side). If you don't find a cause with pressure testing, and you have a head that is vulnerable to porosity, consider removing the rocker covers and repeat the pressure test. On the other hand, more common causes like a leaking radiator, water pump gasket, or hose are still more likely.

[@kevinkrooss3011]

Nice find! I have this symptom. Also I smell coolant when I come to a stop.

[@spelunkerd]

If you smell coolant in the cab of the vehicle, check the floor mat on the passenger side for wetness. The heater core is a type of radiator that can leak coolant and give a moist smell. Unfortunately it can be hard to reach, labor to replace a heater core can be significant.

[@GTD_Y2]

Thanks, helped with my '04 Suburban. Totally redoing my Suburban. Why Pay $80K for the new junk their selling today.

[@kurtisross1715]

Really good info, thanks

[@Wakeywhodat]

I have the 05 Tahoe 5.3 (250k miles). Every time I fix a leak a new one arrives. Current leak is closer to the driver side right near the firewall. I tried for awhile with a mirror and light but could not find it.

[@Taekaera99]

Had this issue with an old van and it turned out the radiator was 90% clogged and the high pressure was blowing the coolant system all over.

[@basspig]

I just got an '05 Silverado 2500HD last week. When I got it home, during a system checkout, I found I had no heat. That turned out to be low coolant. I added a gallon of antifreeze and the heat worked fine. The thing that concerns me now is that I'm seeing excessive steam from the exhaust and there's a sickening sweet odor, not quite your normal cat converter smell. That has me thinking that the engine may have a head gasket problem and that I should contact the seller and let him know there may be a serious problem. 35 years ago, I had a head gasket leak on a '69 Buick Riviera and the engine grenaded while on the highway, utterly destroying it totally. It turned out to be a head gasket leak responsible for the piston hydrolocking. I just got this truck and now I'm concerned it may be a few miles away from a major catastrophic failure if I drive it.

[@spelunkerd]

Gotta wonder how much the seller knew, it is hard to ignore a persistent coolant leak.

[@basspig]

@@spelunkerd Well I got the truck registered today ($445.09!! not including sales tax!!) and drove it to a couple of places. No steam out the exhaust. Now I'm thinking it was the low dew point and near 100% humidity that was creating an unusual exhaust condensation condition as I had a big cloud of what seemed to be steam lingering around the back of the truck last night. Today, nothing. But there is a smell of antifreeze near the engine compartment, so there is a leak somewhere. Just how much, I don't know. But the radiator hose was not hard or under pressure this morning when I checked it, so that's a good sign.

[@spelunkerd]

@@basspig Good. You might have a look under the oil cap, condensation there is common and some of the earlier models of this truck had issues with head cracking/porosity.

[@basspig]

@@spelunkerd Oil looks fine, no white foaming or other unusual stuff. Looks freshly changed, but prior owner says it's got 2000 miles on that oil. Same goes for the tranny fluid. Clear pink, like just changed. Truck runs great. But there is a coolant leak somewhere. It loses a noticeable amount every day.

[@jamesmarek3227]

Heated coolant is routed thru the throttle body to prevent freeze up during cold, humid weather driving. Older engines used exhaust heat to prevent freeze up.

[@ezas123ful]

Hmmm, … I have this problem. Your explanation makes me wonder …. Since I live in Southern California very dry and mild …. Would it be reasonable to bypass the coolant flow through the throttle? Just a thought; first I’ll try fixing it.

[@gamingforhumanity6659]

I found your video helpful simple and easy to follow

[@devinmccloud]

Same issue 2002 silverado. No overheating, coolant smell, coolant loss in resavior, and 102k miles.

[@spelunkerd]

If the smell of coolant is present in the cab, check the floor mats for wetness that might be found if the heater core were leaking.

[@brodheadjim]

Thank you for a very helpful video for us rookies.

[@bobbarron6969]

My 2001 4.8 has a mystery leak. It would be so nice if it was a hose and not a head gasket. Next, get my hands on a pressure tester. Thanks for the vid.

[@spelunkerd]

I'm told that some autoparts stores will loan them out for a deposit. This version of the GM engine has an unusual sized cap and it can be hard to find the right adapter. The other option is to find an inexpensive generic kit online.

[@MilesofProof]

Extremely helpful, especially the 2 intake/throttle body hoses that are left unmentioned in repair manuals........

[@toniolson2497]

I will check mine tomorrow, I have a mystery leak on an ‘05 Tahoe.

[@Wakeywhodat]

Did you find the leak?

[@Andrew-B_eZ]

I’m loosing pressure in my 05 Tahoe and boiling over my resovior I can’t find the leak anywhere

[@Wakeywhodat]

@@Andrew-B_eZ Could it be a blockage? I keep having leaks on my 05 Tahoe, I’m starting to wonder if I have a partial blockage. I have to do the intake gasket next.

[@frankiereed3861]

Radiator

[@candicebeebe6688]

The pressure gauge should have shown a pressure drop. And who put the aftermarket hose clamps on ?

[@spelunkerd]

That's a good point, I didn't wait long enough for the one drop every 30 seconds to result in a pressure drop. Especially when there's a little air in the system, pressure change with volume gives a blunted response which can be hard to distinguish from the normal sag in pressure from aging seals on the pressure testing equipment itself. Any diagnostic test will have false positives and false negatives, so you need to roll with the evidence and understand what info to shrug off.

[@davidpage7025]

Had a leak forever good tip

[@ozielpulido9545]

A quick tip when removing those hoses under the throttle body use some small vicecreap ply iré to prevent from loosing to much coolant..

[@spelunkerd]

Good point. I have a set of small needle nose vice grips with rubber hose on the ends so that rubber tubing doesn't get damages when crimped. Honestly I didn't expect this one to drain much, it drained more than I expected.

[@troyfisher3775]

That is the design they built for the cold climate these trucks are built in canada so it is warm water to keep the trottle body to peform like it should in the weather up in the northern states ....

[@spelunkerd]

As stated in remarks below, coolant warms the throttle body to get sensors and the throttle plate warming quickly. I've been looking for a good explanation for why this LM7 variant of the Vortec engine has crossover piping that ultimately sends coolant/steam to the throttle body, then back to the rad. Chev abandoned those crossover pipes in later years. For a good video explanation of why these 'steam pipes' are there, try this KZbin video kzbin.info/www/bejne/m2PCpaqpdt-ckJI. It explains a lot, also including remarks about the unusual design of the thermostat and water pump.

[@stevea6722]

I'm late to this video but the cooling is probably because on the earlier models of the LS style engines there was EGR that was plumbed back into the intake at the throttle body. On later models ~2005(?) on up, the EGR was deleted by the GM engineers, obviously not needed hence the cooling bypassed the throttle body.

[@spelunkerd]

@@stevea6722 That's an interesting thought!

[@ezas123ful]

I also have a mystery leak (2005 chevy Silverado 1500 4.8) ; the fluid only disappears down to a certain level in the reservoir tank and no further. But, that is enough of a loss that the engine runs hot and get very close to overheating. Also there is no visible evidence of puddling or otherwise. I’m taking the advise of your video and focus on this hose connection. I hope it works for me. Note: my throttle body hose connection has the ‘squeeze clamps’, yours had the ‘screw strap’ type. Those clamps on yours don’t appear to be original (? Idk).

[@spelunkerd]

Yes, I added those clamps. If you're overheating the game is more serious. It may be simply from trapped air, but overheating can be from various other issues. You can even get coolant loss from overheating when the valve on the pressurized reservoir cap decompresses. Two 'easy fix' diagnoses are a bad cap and a bad thermostat. The Chev thermostat also controls bypass flow, and if that bypass tract sticks open you can run hot. If you can't come up with a diagnosis I'd look for a second opinion from a shop before it is too late. One thing that could cause a plateau of coolant loss would be a cracked reservoir tank.

[@mtkoslowski]

Great information. Thanks. Liked & Subbed!

[@pcicraftsman8472]

GOD BLESS YOU MR THANK YOU THANK YOU THANK YOU SOOOOO MUCH. dude you found my leak that I've been chasing for a while 😆 THANK YOU SO MUCH GOD BLESS

[@مهندكهربائيسيارات]

جيد احسنت استخدمت الضاغط بشكل رائع

[@spelunkerd]

Thanks!

[@marksteven3534]

He say's "Well done well compressor was great" (google translate) I would agree

[@heartlandmechanic]

Nice job .

[@spelunkerd]

Thanks, man! When I discovered I have 706 heads, I was wondering about bigger problems. Fortunately this one was a simple fix.

[@droid73rs]

Gonna have to check there Ive got a sloshing sound now from my passenger side dashboard i have a feeling i have a bad heatercore 01 Tahoe 200k miles And yes they pressure tested it last year!

[@spelunkerd]

Yeah possible. Any cause of trapped air will do this, always start with burping and checking seals, hoses. I did another video of a mystery leak in my Dodge Ram. Turned out to be a pinhole hose leak in one of the heater core hoses, very hard to find. Good luck!

[@brandondye3459]

I'm dealing with the exact same issue with my Silverado. May I please ask how you plugged up the vent hole? Nothing I'm using is working. Thanks!

[@spelunkerd]

Normally with the cap in place, the vent is automatically plugged by the cap. To pressure test the system, the ideal solution is to use the correct size cap adapter, but those can be hard to come by. So, when I did this test I simply used a rubber cork I had on hand to plug it temporarily. As you know it normally needs to be left open so if there is an overheat there's a pathway for steam to escape when the cap spring gate is opened.

[@brandondye3459]

@@spelunkerdYes sir. I should have been more specific, I'm trying to pressure test mine as well but can't find a good solution to cap the vent so I can maintain pressure for the test. I'll go on the search for some good rubber corks. Thank you so much for the quick response. :) Cheers!

[@spelunkerd]

@@brandondye3459 Yes, I thought so. I put those explanatory remarks in for others who might stop by and misunderstand our conversation.

[@Dusty2040]

I have a small leak near the front left of the head engine seems to run hot but never to over 210 is it a head gasket?

[@spelunkerd]

Head gaskets can definitely leak either coolant or oil to the outside, as can a cracked cylinder head. Coolant can also leak inside the head and drain by gravity into the oil pan, causing your oil level to be unexpectedly too high. If it is purely a leak to the outside without leakage into a cylinder or oil passages, your problem will be either a mess on the outside of the engine, or drained coolant with secondary trapped air. You want to avoid trapped air by keeping the coolant reservoir well topped up so as the engine cools overnight the air is replaced by coolant from the reservoir. Trapped air is a problem because it can cause localized overheating even if the rest of the engine is OK, and the water pump may be less efficient at moving coolant. I would have it inspected by a mechanic as soon as you can, to avoid letting it get worse and possibly killing the engine. The 5.3 LS engine series have coolant bypass tubing in the top middle of the engine which can also leak, so identifying the source is critical. As shown here, you might be surprised if coolant happens to be dripping down from another source.

[@marcglenn3051]

I had the same issue and discovered right where the thermostat joints into the antifreeze tank and heater hose that plastic joint with those plastic or rubber clamp that plastic joint had a hair line Crack in it , also it had become dry rot I'm buying a metal joint to join those 3hose together Sound like they where trying to save money and cut cost you ask me

[@MrWalkman99]

@ 3:56 is that the coolant leaking?

[@spelunkerd]

Yup. I made a little fountain when I pulled that leaking tube off, even though I decompressed the pressure and removed the pressure tester from the reservoir. Pressure imbalance from inside the cold engine drove fluid to escape, for some reason. I was ready to cut the end of the tubing down and so quickly replaced it, then mopped up the mess of coolant on the garage floor, ha ha.

[@MrWalkman99]

I’m working on my GMC truck and am having the same issue. THANK YOU !

[@invaderzim133]

I loaned one of these from my local advanced auto and none of the caps fit my radiator so used one of the universal ones the kit came with. The system held steady at 15psi the whole time and I couldn’t see any obvious leaks. Pretty annoying I know I have a leak as I always see it dripping around the transmission and have a small pool under the truck. Oh well..

[@Tabstarbelle]

Dave, I'm losing coolant in a 2001 Tahoe, but there are no leaks that can be found. Oil needs to be changed, but it is not foamy or milky, so the coolant is not going into the engine block. Light came on. Added coolant. 2 miles later, shut the vehicle down, was inside the bank for about 30 minutes. When I came out and started the vehicle again, the LOW COOLANT light was back on. I've had someone check for leaks with lights and none can be found. What can be the problem. What is involved in trying to determine a head gasket leak? How would I be able to tell if it is a water pump gasket or other issues? I am a widow and not a mechanic. I feel like some things I have been told may not be correct. Feeling like I'm getting 'scare tactics' used on me to get them to do engine work. Any suggestions? Would I have any better luck at a dealership. (337,000 miles on the engine). I dread the cost, but I need to keep the vehicle on the road. I do not drive very much or very far and certainly cannot afford NOR do I want a new vehicle (too many bells and whistles on new vehicles for me). HELP PLEASE.

[@spelunkerd]

I would not jump to the conclusion of head gasket leak. The most common cause of leaking coolant is a leak at the radiator, usually easily found with a light and mirror, often at the side where plastic meets the aluminum heat exchanger. Following that, hoses can leak, the water pump can leak, the reservoir cap can fail to hold pressure, and even the heater core can leak coolant onto the passenger side floor. In addition this generation of chev engine had a problem with porosity of the steel that heads were made from, which can also leak. I would not take it to the dealer, I would look for a local shop that does general mechanical work. They would likely do the pressure test I showed here and most of the time would find a diagnosis. If nothing is found, I would continue adding coolant to keep it well topped up, continue to drive it, and wait for more clues.

[@christianfloresjr5097]

@@spelunkerdI have the same 2000 suburban with a mystery leak. I completely changed all hoses, new radiator, just did the thermostat (twice), new water pump. I put new gaskets on the valve covers and found milky oil in the valve covers. But no milky oil in dip stick. I have to add coolant every 2-3 days now to top it up. I do hear a tick in the mornings when I start it up in cold start and it goes away when it’s warmed up. I’m thinking maybe I got a defective water pump. But ima change my radiator cap first to check if that’s the issue. I do get some white smoke at start up but not too much. Any ideas, please help! Thanks in advance. And God bless.

[@danielaa8781]

So this is also happening to me, im having to add coolant every 2 weeks when is cold, monthly during hot days. Already changed thermostat, water pump, entire new ac system, im out of ideas as to where is the evaporation coming from because is not a leak... Any suggestions sir? The hoses also appear to be ok

[@spelunkerd]

Careful inspection looking for crusting residue from evaporated coolant can sometimes help find an obscure leak. Look for damp floor mats, that might suggest a heater core leak, and inspect both sides of the radiator especially the sides where leaking plastic connections are very common. Have a close look at the weep hole of the water pump, and while you're at it look for leaking around the coolant reservoir. It could be as simple as a bad radiator cap, that can leak gas, which presents with occult loss of coolant. If you keep the system topped up the risk of overheat is pretty small, although I would carry a container of distilled or deionized water to replenish fluid if it leaks away from home. Never remove the rad cap of a hot engine, the risk of superheated burns is too high.

[@danielaa8781]

@@spelunkerd Thank you so much sir for such detailed information. I will definitely take a look, I did also replaced the radiator but have never checked out the hoses closely. Thank you for an amazing video!

[@chass5438]

@@danielaa8781: You can't just start changing out parts to find an answer. You have to find the problem first, then get the part that's causing it. I was just like that until I finally thought, that's not how you should do it. Luckily when I did do that they were cheap parts, nothing major.

[@mrt6897]

What are the casting numbers on your heads? could be the infamous "Castec" head coolant leak due to small cracks in the heads . think 862,706 were the casting numers affected and mostly on the Castech made heads.do a search online for castech head issues. bye

[@kalebjeppson2333]

Where did you get your pressurizer?

[@spelunkerd]

First one was Astro, in the mid 90's, I think through an automotive parts store. It was missing caps for some vehicles (like the somewhat unusual GM vehicles of the mid 2000's), so second one was a chinese brand through Amazon a few years ago. The chinese pump isn't great but the caps are fine.

[@GGarcia7111]

Outstanding!!!

[@spelunkerd]

Thank you! Cheers!

[@trjonez]

Said hoses are to keep throttle body from freezing up the throttle plate in humid freezing temperatures.

[@Gabagoolll471]

I have. 2019 suburban that was leaking and overheated so I refilled it and so far so good. If it leaks again what could it be

[@spelunkerd]

Make sure you burp the cooling system to clear it all of air, trapped air is a common cause of overheating. Basically to burp you simply leave the radiator (or in this case the pressurized cooling system reservoir) open to air while you warm the engine up. While working it up you need to stay on top of it. The most common cause of a leak is a bad radiator, commonly at the edges where the plastic housing meets the aluminum core. Other causes include leaking hoses, a leaking water pump, bad hose clamps, leaking heater core, etc. I did a whole cooling system playlist, including many videos taken of this very vehicle. New vehicles have moved to electric radiator fans, so make sure those are turning on in the heat.

[@Gabagoolll471]

@@spelunkerd thank you. So after 10 miles it started loosing coolant again but it’s not showing on the ground. Is that a bad head gasket issue waiting to happen? Should I try devil blue sealer. It has 180k miles

[@spelunkerd]

@@Gabagoolll471 Don't add any form of stop leak or sealer. Keep adding fluid, at this stage I add distilled water to save money but you could use tap water while you're trying to work it up. You may need to remove plastic covers underneath to get a good look at the water pump and the underside of the cooling system. You want to use a mirror while the vehicle is off and find the weep hole on the bottom of the water pump. Feel the floor of the passenger front seat for wetness, and use your nose to identify a coolant leak there. Park over pavement where you can identify leaking fluid, but remember the AC system will normally drip plain water, too. Coolant that evaporates will leave a crusty mess, look for that.

[@Gabagoolll471]

@@spelunkerd ok thank you sir. It’s either head gasket or water pump so we’ll see

[@ironfist3122]

I have a 2004 we hitch is losing coolant and I have already changed the reservoir cap recently. What else could it be and should I do a pressure test? If so can I rent or do one at autozone?

[@spelunkerd]

Some autoparts stores will rent equipment like that out. In the meantime, check the radiator, coolant reservoir and all the hose fittings carefully, looking for a wet spot. Sometimes you only see discolored crusty residue around a slowly leaking component, such as the plastic coolant hose flange in the Jetta, a notoriously common problem. Don't forget to look underneath the water pump for the weep hole, if it is leaking there you need a water pump. If the cab is unusually damp or smells of coolant, it could be the cab heater core. Usually if it is more serious like a head gasket you'll have other issues, such as white smoke out the exhaust or recurrent overheating even when coolant is well topped up. Occasionally I've had vehicles that don't show me the diagnosis, in which case I top up the coolant frequently and wait for more clear signs to evolve. Don't be tempted to use StopLeak, those compounds cause more problems than they solve. Good luck!

[@pughconsulting]

My only criticism, and it's a minor one, is to use anything other than worm-drive clamps. Spring/tension clamps or fuel-injector hose clamps are much better at evening distribution of tension around the hose. They're fairly inexpensive when ordered in an kit of various sizes, then you'll always have them on hand.

[@spelunkerd]

Excellent point, I've been slowly coming around to that perspective now for years.

[@abdou1284]

I hope you tell me from where err i can get the compression tool you used. Or any reliable one Thanks

[@spelunkerd]

The kit I have is no longer sold, it is by Astro Tools. The present version is more inclusive and over $250, but even so they don't include the cap for late model GM vehicles. You can buy knockoff kits, search "coolant pressure tester kit" and choose one that is right for you, cost is ~$60-150. Those new kits are better because you can do vacuum filling, they have more caps, and you can actually test some caps. Unfortunately the trend in automotives is for every manufacturer to use a different rad cap, which is annoying! Another option would be to ask at your local automotive parts store, who may offer to lend or rent a kit to you for the day, for a lot less. Or, you could buy a new cap and make your own kit from a bicycle pump, etc. Or, you could VERY carefully run the engine and look for the leak with engine running. Watch out for electric fans that will turn on without warning, moving belts, and hot exhaust components. Good luck!

[@abdou1284]

@@spelunkerd thank you very much. 🌹

[@spelunkerd]

@@abdou1284 You're welcome. You should edit your first message to delete your phone number. To edit, roll your mouse over your post, three dots appear. Roll your mouse over those three dots, and click. A drop down menu appears, click on the edit tab. Then remove the numbers, so you don't get unnecessary spam coming through your phone, then click the save icon. Cheers!

[@abdou1284]

@@spelunkerd Done with pleasure 🌹