VW MK4 JETTA - figuring out coolant leak mystery

Changed out the coolant in my TDI Jetta, then it developed a leak somewhere. Coolant was vanishing without a trace. No visible leaks anywhere so it was hard to track down. Had an idea, so I tried something to see if I could isolate the problem.... Links for coolant used- advanceautoparts.rt8x.net/c/2...
And here- advanceautoparts.rt8x.net/c/2...

[@d3w4yn3]

You just saved me a complete radiator replacement!!! My top hose was split, but I thought it was split on the radiator side, as part of the radiator. It was actually split on the host clamp that you pulled the clip out of. Your close photography of this part and going through the whole system, and having very good video and very good instructions bailed me out!!! THANK YOU!!!

[@Smittyschannel]

glad to help! thanks for watching

[@MrAlistarMusic]

I am having the same exact problem right now. This video was the best on out there by far! Sidenote. Thank you for explaining things in a calm easy way, not doing fast confusing edits. This video helped me out!

[@Jesus-hx5vg]

Thanks so much for this

[@jfarinacci0329]

Very good video. Thank you.

[@mambastu]

Great video. Can you remember what size barbed joiner you used ? I've got a mystery leak on my TDi too...

[@adamgeorge2982]

I got a 1.9L PD engine. When the front end is raised up the leak seems to be dripping from the front-most hole on the frame rail. I put in a new heater core and a new cooling pump to solve this issue but I still have the same issue.

[@HardWhereHero]

Did you check the coolant flange with the ECT sensor? They can warp and cause a very very very small leak that might not be noticed because it gets burnt off when it hits the transmission. A telltale sign of this is having a white flaky looking crust on top of your transmission it'll also resemble like a pink tint if you're using the pink or purple coolant.

[@Smittyschannel]

thank you! I will def check that out

[@jfarinacci0329]

thank you

[@aaronleatherwood753]

Interesting that the inlet side of the heater core connection was clean and the outlet side had some gray particulate on it... I wonder if that is an easy quick diagnosis for a probably failed heater core?

[@Smittyschannel]

Turns out either the inlet or outlet cap had a crack in it & was the source of the leak

[@tjj6583]

I have a coolant leak behind the engine on the firewall just under these two hoses going into the firewall where you pointed If the heater core it bad would it leak in the same area or inside the car. My heating works but I'm adding coolant quite often.

[@Paigenparkinson]

Did you figure out what the problem was and what the fix is? I’m currently having the same problem! Driving me mad that I can’t work out what it is

[@kingCRUISErFJ]

I’m having a similar issue on my 02’ alh. I get excessive pressure in my upper radiator hose then coolant leaks from the upper radiator hose where it’s attached to the block/coolant glow plug housing. replaced the hose clamp, no luck. Replaced the thermostat with no luck. Replaced the cap on the expansion tank with no luck either. I just tested Head gasket with the special blue fluid and it was fine. I’m not getting a constant flow from the return into the overflow bottle, even after 2 cycles of “heating it up to temp” while pumping/squeezing thermostat coolant hose and upper radiator hose, capping it and letting it cool down to draw coolant in. I put up to temp in air quotes because it wont get to 190. I do have heat strangely, but it will drop the temp slightly when on. Im curious if i have an airlock or clog in my system, either way, would a flush be the best move or am I overlooking anything? Any help is appreciated.

[@Smittyschannel]

I vent mine by keeping the cap off the overflow globe & letting the hose bubble into it like in the video. If it's been a few years since a flush, I would def do that. I had to put cardboard under mine to find the leak- it wouldn't leak enough to be noticeable on gravel in my driveway

[@mervinwestby35]

Question: will this cause the AC not to work? I knw with some cars, the AC don’t work when you’ve bypassed the heater core because the car temperature is too cool as it should run on a temperature. Did this happen when you bypassed the heater core or the AC still work as normal?

[@Smittyschannel]

My AC doesn't work, so I could not tell you. I am in the snow belt, so I would not have my heater core bypassed year around. This was just to isolate the leak.

[@JMoriki808]

I bypassed my heater core after one of the plastic connectors broke. I live in Hawaii so no need heater. Lol. My a/c is still as freezing as it always was. Just did this to my friends one as well and his a/c still works too.

[@mannyfernandez6860]

jury rig an old radiator cap with a tire nozzle tip and let her fill up with air...dont worry that a line will burst , THAT is actually your intention.

[@jessefitch7032]

My vr6 is leaking as well. But the leak is running from somewhere on the same side as the reservoir. And suggestions? I seen it running down the side of the oil pan so that was my first assumption. The reservoir needs to be replaced because the return hose fitting is broken but idk if that would cause such substantial leaks when it sits. Maybe though. Thanks for the vid 🙏

[@Smittyschannel]

Check to make sure all your hoses are connected properly, & not cracked or leaking as best you can. You can spray them with starting fluid a little to dry them off, or dry them off with a rag, etc. Then look while it's running to see if there's any dripping

[@retrop_n552]

Could be the water pump, did you ever figure it out? My vr6 is leaking in the same way

[@retrop_n552]

@sweetstarize if you can’t see the leak hit the ground, your heater core could be leaking which is inside the dash

[@donlive2758]

TIP... tie some fishing line to those clips on the hose joints,,, that way you won't lose them as they can go flying if you snap them open too far or fast... it happened me ,,, loosing 2 of them,, then i thought of the fishing line. also you should have coolant in the car if the core is leaking,, wet carpets ...

[@Smittyschannel]

no wet carpet as of yet

[@christianbowders2194]

I have an 02 vw Jetta 2.0l that leaks coolant just as bad as that wonder if it's the same thing is the heater core even a vital component of your vehicle?

[@Smittyschannel]

Unless you tear out the heater core it's hard to tell 100%. It took 7 hours to tear mine out, only to realize it was ok, & the problem was somewhere else. Tell tale signs of leaky heater core are misty steamy vapor coming out of the vents, & / or to bypass it like I show in this video & check your coolant level after a few days.

[@aztecahernandez6539]

You forgot to putt the clamp back on the small hose in the reservoir.

[@Smittyschannel]

It stays put as is; you have to tug on it to get it off, so it's fine for now

[@abepenner4714]

I have a coolant leak in my 2000 tdi jetta right under the bumper passenger side.. waiting for a bit warmer days to dive into it

[@liamj3146]

I have the same problem, did you ever look at it?

[@LawrencePina]

On my 2005 Golf, coolant leak right under the bumper passenger side was caused by corner corrosion at the bottom of the radiator, and by a failed O-ring on the washer pump. To my surprise, both pink and blue fluids collected in the pan I put underneath. Replacing the radiator and the O-ring ($500 at a local shop) solved both problems. Hope this helps.

[@CANERm3]

Did you check Waterpump? It looks like there is no circulation, you can easy check removing Thermostat housing for waterpumpimpeller it can separate from pump shaft.Btw i have the same car with same Engine.

[@Smittyschannel]

water pump was replaced 30k ago- last one made it 200,000 miles. If water pump wasn't working properly coolant temps would spike. It's currently in the shop getting checked, so I will update when I get it back

[@paxmaponga733]

Question can you put actual water in that there coolant bottle only water I mean ?

[@Smittyschannel]

you can (you should use distilled water), but be sure to keep the overall mixture around 50-50 with coolant & water in the system

[@rmendes2mendes915]

Should be a steady flow coming from that hose on coolant tank once bleed if not you have a restriction, possibly bad water pump.

[@Smittyschannel]

After the engine has run for maybe 5 minutes, the stream becomes continuous after bleeding it

[@mybigbackyard741]

Did you ever figured out where the leak coming from?

[@Smittyschannel]

it is on the back burner at my mechanic's shop- hope to get it back this next month or so

[@Smittyschannel]

Update! Finally figured it out. Every once in awhile it would leave a puddle on pavement that was noticeable. Turns out the bottom corner of the radiator was rotted out, & finally I could see a pink tinge on the bottom fins (slowly getting worse). Apparently a number of things were contributing to my dilemma. Stay tuned for a radiator replacement video 🙂

[@asilentvoice9004]

What will happen when the radiator is open you press the gas pedal

[@Smittyschannel]

sometimes it will surge upwards & overflow all over the engine

[@titorojas333]

My friends 2004 jetta is leaking lots of coolant we replaced one of the heater core connectors because it was leaking but it did not fixed the problem. Tomorrow we will inspect it again but this time I will try my best to check his water pump, base on your responses it seems the heater core replacement did not fixed the issue and now it’s been over a year, what was your leaking issue and what did you replace to solve it. Thank you very much!

[@Smittyschannel]

I believe it was the plastic connectors that attach to the heater core- they were old & one had a crack in it, slowly losing pressure & weeping coolant

[@titorojas333]

@@Smittyschannel The leaking problem was definitely two things: a Tiny hole was in the hose that connects to coolant sensor we replaced and the other issue was his water pump it was leaking pretty bad it was dripping on one side of the o-ring seal when he arrived this morning. I suggested to replace his timing belt, tensioner, and water pump all together since we were going to remove that freaking pump. After seven hours (thank you Autozone for fucking up they gave the wrong parts: TDI kit) of driving around searching for the correct parts it was all done and no more leaks!!!!!

[@Smittyschannel]

@@titorojas333 Glad to hear that- it's definitely worth changing the water pump while you're already in there for the timing belt

[@titorojas333]

@@Smittyschannel hope this trend helps someone 👍🏽

[@cman3107]

Hello thanks for your video, I have a problem where I was loosing level and gaining pressure in my coolant, I first changed my expansion tank and cap was still getting pressure, I'm currently at the point where I have bypassed the heater core and looped my 2 pipes together, The level now hasn't gone down so now I'm thinking time to change the heater core I was thinking maybe it is blocked so I think I will try clean my heater core and go from there, What was your end result did you replace the heater core and did it fix the problem? Thanjs in advance 😊👍

[@Smittyschannel]

I did replace my heater core; that will be an upcoming video. It however did not fix the coolant leak in my case. I took it to a shop where I am awaiting a diagnosis

[@BigDamoS]

@@Smittyschannel any updates on the jetta?

[@Smittyschannel]

@@BigDamoS still in the shop; has been on the back burner for me as I work on other projects currently. The turbo had a boost leak & needs rebuilt, along with brake booster replaced too.. $$$$

[@BigDamoS]

@@Smittyschannel oof, im going through a similar coolant issue with mine so was hoping you figured it out, Thanks for the reply!

[@titorojas333]

My friends 2004 jetta is leaking lots of coolant we replaced one of the heater core connectors because it was leaking but it did not fixed the problem. Tomorrow we will inspect it again but this time I will try my best to check his water pump, base on your responses it seems the heater core replacement did not fixed the issue and now it’s been over a year, what was your leaking issue and what did you replace to solve it. Thank you very much!

[@kcummo]

Ever figure out the problem?

[@Smittyschannel]

I later changed the heater core (that's a big future video), but the old one looked fine. I'm still getting it looked at

[@user-ru1fx2wj6t]

What is problem bro ?

[@Smittyschannel]

After replacing a few things, I think there's a pinhole in the bottom of my radiator somewhere

[@billcomeau5408]

Check your oil cooler & the 2 gaskets. This is a cheap repair & the oil cooler failure can cause the antifreeze to slowly leak out. You can grab an oil cooler for around $25 online.

[@Smittyschannel]

Thanks! I will check that out

[@catrachan]

Hey man! I was just checking my 2.0 2004 Jetta, new to me, I just saw the oil cooler above the transmission and is all moist, also underneath you can see the transmission oil pan also moist, what you mention could be the issue as I started smelling coolant and that’s why I was checking for leaks… is it an easy DIY?

[@maritzavargas9908]

Did you solve the problem?? any updates? Thank you

[@Smittyschannel]

It's at my mechanic's shop awaiting repairs still. Apparently it's not the heater core because I replaced that & the fluid level still drops in the reservoir globe. Doesn't really mist out the tailpipe, so it may not be a head gasket, unless it's a tiny amount. It honestly has me baffled at the moment

[@dahbeh9975]

@@Smittyschannel eva look into egr cooler, like you mentioned in vid? mines giving P3130 (egr, had vdubb mechanic look into it over month ago) and today went limp mode with same fault code. id suggested mechanic look at egr cooler, but he found it too hard (its a beetle) so he looked at the inter cooler instead... also, just had a different mechanic change thermostat, in case it was faulty in the closed position, it would not allow ...

[@rootz420]

What if u do have the creamy nastiness?

[@Smittyschannel]

then you likely have oil getting into the antifreeze, & probably antifreeze getting into the oil. #1 suspect is the head gasket. How much nastiness you have usually determines how big the leak is

[@rootz420]

@@Smittyschannel a ton of cream. I pressume its the oil cooler.

[@Smittyschannel]

@@rootz420 could be that too- oil cooler O rings are notorious for going bad

[@rootz420]

@@Smittyschannel i think by the amount of cream its probably a lot of both.

[@Smittyschannel]

@@rootz420 Oil cooler is the easier of the two; maybe start with that one, then change your oil. After a few days of driving, check it each day & see if you're still getting it