1.8T B5 Passat & B5 Audi A4 Cooling system clarification

Thomas
P.O. Box 83041
4827 Kingsway
Burnaby, BC
V5H 0A4
Canada
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[@Friebe1000]

Just saved me big time on a b6 a4. Thanks for the clarification. I wanted to call it a dead water pump, now getting a thermostat and a heater core flush

[@EXOVCDS]

Thank you for watching!

[@BruceLyeg]

I'm glad you cleared that up. I've been thinking about it for days, almost ruined my weekend.

[@EXOVCDS]

You're welcome... get some sleep now!

[@stuzman52]

Good lesson in describing the flow of coolant. I think you are a great teacher and one can’t think of everything. Have a great weekend of what’s left. 😀👍

[@EXOVCDS]

You too Terry!

[@kawakami7972]

i've watched a few of your videos (the whole way through btw. Not just a few minutes each lol), and even though you say you're not a teacher, you have taught me so much. Like you, I am also a visual learner. This overview was so great, thank you as well for stopping the video to draw an arrow at the bleed hole. I wish there was more available videos similar to yours. I have a 03 Passat edit:B5 1.8T (AWM). currently scraping the internet to get info on replacing the coolant flange. Edit: dancing baby at the end is cherry on top XD

[@EXOVCDS]

Thank you for watching! kzbin.info/www/bejne/nJmVinVtnZyksLM

[@TheRebuilt1]

Great information and analogy of twin circuit operation of coolant system with open and closed thermostat. Still taking us to school sire.

[@EXOVCDS]

As long as I don't blabber too much... I won't step on my own toes! LOL

[@patkelly7999]

Good simple clarification Thomas:)

[@EXOVCDS]

Thank you.

[@warrior13shadows]

I did and it worked perfectly thank you so much!

[@EXOVCDS]

Thank you for the update and thank you for watching!

[@wyattoneable]

This will certainly help many people who stop by.

[@EXOVCDS]

I hope so.

[@FattyJoel]

this video was actually very very helpful too me.

[@EXOVCDS]

Thank you for watching!

[@TheDisgruntledMechanic]

Thanks for the clarification! Now I will know when I work on one! probably never!

[@EXOVCDS]

Yeah.. I bet you'll see one next week! LOL

[@upkarbath]

Great job explaining.

[@EXOVCDS]

Thank you for watching!

[@warrior13shadows]

I didn’t know there was a bleed screw there this helps a lot !

[@EXOVCDS]

It's a bleed hole... you have to loosen the hose and slide it off of the heater core pipe until the hole in the hose is exposed.

[@danielsalt363]

Great explanation 👍

[@EXOVCDS]

Thank you and thank you for watching!

[@DylanRabier]

Good info. Thanks for sharing! 👍

[@EXOVCDS]

Thank you and thank you for watching!

[@warrior13shadows]

Thanks for this video

[@EXOVCDS]

Thank you for watching & taking the time to comment!

[@enginehobbies9483]

Great info all the way!

[@EXOVCDS]

Thank you and thank you for watching!

[@enginehobbies9483]

I have to say, I was never to sure how u tubers were paid until I seen an explanation on one of your videos. I watch them all straight through. It's great work. Thanks for all your time.

[@EXOVCDS]

Much appreciated!

[@albertoalmonte6131]

Thank you,thank you 4 this.

[@EXOVCDS]

Thank you for watching!

[@mikeklamecki7510]

Thanks!

[@EXOVCDS]

Thank you so much! Thank you for watching!

[@CarsExposed]

Nice explanation mate, i wish I could go back in so many videos to add stuff or change etc and I was thinking 🤔 does it happen only with me 😊👍👍👍

[@EXOVCDS]

I keep telling myself... no one will notice / question things. So far I have been correct in thinking that way, but I feel bad when information like this could have prevented some frustration to someone I was helping.

[@eperry8496]

Good Info

[@EXOVCDS]

Thank you for watching!

[@kyhomegarage3430]

This was great explanation of VW cooling system my friend. Thank you so much. I have 2011 Audi A6 with 3.0 with overheating problem. It will overheat in city or highway speed no difference. Cooling fans are working, no leaks in system at all, well maintained car. I did notice if I rev engine over 2500 RPM temp will drop down. Could this be failed thermostat or is there something common on these engines I need to check. Thank you sir

[@martinee4901]

Bad Coolant been used & the water pump vanes have disintegrated. Look for black plastic flakes in the coolant. = New waterpump. If waterpumps not working right, it won't circulate warm coolant into the overflow bottle either.

[@naushadali95]

great vinformation

[@EXOVCDS]

Thank you for watching!

[@DeathByHankie]

Thanks for a great video! Would it be correct to assume I have a thermostat stuck open if that coolant stream into the reservoir is visualized immediately with a cold engine? Just brought a 2003 Passat 1.8T back to life after a 10 yr slumber. It takes forever to come to temp, and then drops quickly to a very low temp when driving in cooler weather (turning on the heater drops the temp as well). Suspicious of air in the system as well --- complete noob ... looking forward to checking the coolant stream and hose temps after watching your video ... which I prob need to watch a couple more times to really sink in.

[@EXOVCDS]

Yes, sounds like a stuck open thermostat. Thank you for watching!

[@DeathByHankie]

@@EXOVCDS Thanks for confirmation you really painted a clear picture ... if this car wasnt my backup I'd be moving to BC!

[@kyledpiper]

Hi Thomas, I have an 03' 1.8T AWM. Coolant steamed the car up bad today. Began to overheat so I did the neutral ride, heat on, and limped home for about 1mi. No visible hose leak. The battery bay is filled with fluid, so I was thinking maybe the heater core, before the water pump, thermostat, etc. I topped off with distilled water just to check. Once running, I cracked the reservoir and it backfilled. It took about 5min of running for it to drop maybe from the MAX level to the LOW level. I cracked it again and it filled. The only thing I noticed at the reservoir was that the return was coming in, but the top inch was foamy. Maybe not a head gasket as I did pour in an additive (I know). Interestingly, after the single top-off - there are no more lights or overheating issues whatsoever, at idle OR operating temp at any speed range up to 60mph. Was there something clogged perhaps? A "passed stone". Really odd. I plan to flush and replace the system. The vehicle has 238K and I just replace the oil pressure sensor - runs great.

[@EXOVCDS]

No visible hose leak... the battery bay is filled with fluid. That does not make sense. Any overheating while driving at steady speed, is either due to a thermostat that is stuck closed or a bad water pump. If you had heat inside the car when your heater was on, then your water pump is OK... leaving the thermostat as the cause. If you had fluid all over the engine bay, you have to look for a leak. Plastic flanges can Crack, leak under pressure and seem fine when the engine is cold.

[@kyledpiper]

@@EXOVCDS Thank you for the quick response. I'm due for a timing belt kit (metal propeller on now and in the future). I'll research the thermostat install. I'll try to get it up to temp and pop the hood shall it steam again. Hopefully, I can find the leak. I believe it was on the passenger side, although that could simply be the lowest point, or where it is draining.

[@EXOVCDS]

kzbin.info/www/bejne/fpuvaoNrmL-qbMk

[@2121heatherh]

Great video. I'm trying to figure out what's wrong with my cooling system. Coolant comes out the bottom of engine and hoses and residue are not leaking. Could I caused this issue by not bleeding my cooling system after filling up the near empty coolant reservoir?

[@EXOVCDS]

Follow the leak to the source... then I can tell you what the issue might be.

[@teratonexplosion]

Hello, thank you for your video. I was trying to figure out what is going on with my sister's cooling system, after watching this video it has given me some direction. On her passat(2000 1.8t 20V) there is no coolant exiting the tank. The bottom hose is cold but the top hose is working, however it is overfilling the tank as the water is not cycling and the water is coming out from the overflow valvue. Would a good start to finding the solution to this, will be replacing the thermostat, or it is more likely to be the water pump? Thanks

[@EXOVCDS]

If you have heat inside the car, the water pump is good.

[@j031drumr]

I have a backflush Tee on the heater hose in my B5 that I use for bleeding since I seem to open the cooling system about twice a year

[@EXOVCDS]

Good tip... thanks for sharing! Send me your mailing address and I'll send you some of my channel stickers.

[@j031drumr]

@@EXOVCDS I made a video showing how I did it kzbin.info/www/bejne/pJjUiptpe9emiMU

[@EXOVCDS]

I just watched it... good idea!

[@flatratemaster]

I always forget that about b5s

[@EXOVCDS]

Main reason I always vacuum bleed these... most of the other engines (2.0, 1.9 TDI, older VR6) I don't bother with vacuum. I just squeeze the hoses (as I fill fluid) to start a siphon effect.

[@mostlymoparih5682]

Sparked your memory aye? Hope it's not combustible. Good job Professor.

[@EXOVCDS]

Come to think of it (ouch)... my brain hurt when that happened. Ouch.... just happened again!

[@zedman442]

I believe there is also an oil cooler if I remember correctly with these engines. Prone to breaking and mixing coolant with the oil, signs of HG failure but not.

[@EXOVCDS]

Yes... pretty much all engines have oil coolers that can lead to a HG misdiagnosis.

[@zvonimirbobic1093]

To clarify the direction of coolant flow..it goes through the upper radiator hose into the radiator, then through the lower radiator hose out of the radiator, provided that the thermostat (which lives on the other end of the lower hose) is open..is that correct, sir?

[@EXOVCDS]

Yes, just like I showed in the video.

[@billpfeffer6954]

How about a 2.8L heater hose replacement? Thanks.

[@EXOVCDS]

Sorry, don't have a video for that. Disconnect hose, remove hose, install hose. Top up with coolant.

[@Alberto.en.Tenerife]

You.re wrong! You are a great teacher!

[@mrc4810]

So if there is flow there when cold that means that thermostat i open all the time (faulty)?

[@EXOVCDS]

Yes. Most likely.

[@Badgertronix]

I thought it all just leaked out of the broken plastic flanges 😂😂

[@BruceLyeg]

Hahahahahahahahahaha!

[@EXOVCDS]

@ Badgertronix That too... that too.

[@adrianmogosanu9044]

Hello i have a problem wih an VW Passat 2004 tdi B5.I had a bad oil cooler on it and a very big amount of oil went through the cooling system.The expansion tank was full of oil.I tried flushing the sistem with hot water a couple of times but there is still a good amount of oil still attached on the hoses inner walls.I tried using a radiator flush and it was not effective.Do you have any tips or methods of cleaning the mess i'm in?Thanks

[@EXOVCDS]

You can use dish soap... Dawn dish soap is used to clean oil off of bird, so it should be safe to use in your engine. cdn.shopify.com/s/files/1/0504/7405/7897/products/236mlDawnOriginalSent_1000x1000.png

[@henryrodriguez4816]

Hey, I have an Audi A4 b5 with the 1.8t and I have overheating problems and I only see one of my fans spinning. Do you know what could be wrong?

[@EXOVCDS]

The big fan is belt driven. Most likely the thermostat or the water pump is bad. Turn the heater on inside the car... run the engine until it gets warm (before it starts to overheat). If you have heat inside the car (blast at full speed) then the water pump is OK and the thermostat is probably bad. If you have NO heat inside the car, then the thermostat is probably bad.

[@jarb688]

great video. Do you slide that heater core hose partially off with the car running and heat on?

[@EXOVCDS]

Yes, but heat on / off doesn't matter... it's an open flow system (no flow control valve). The only reason you would want heat on, is to verify that the air gets hot (confirming fluid is flowing through the core)... if it does not, then the core is plugged or there's an air lock.

[@EXOVCDS]

The hose has a bleed hole. Only slide the hose off far enough until the hole is able to vent air / coolant.

[@jarb688]

@@EXOVCDS I have done that but haven’t seen any coolant come out yet. do you typically do this with the car running?

[@EXOVCDS]

@@jarb688 typically I use a vacuum fill method. You can disconnect the hose fully and add coolant directly into the hose (raise the hose)... coolant will eventually come out of the heater core pipe. At which point you can reconnect the hose.

[@EXOVCDS]

What led you to this point? Coolant change? Thermostat change? Overheating?

[@sandiegojody]

thanks for the info, but how do you properly bleed the system?

[@EXOVCDS]

Detach the heater core hose that has a small hole in it... it is meant to let air out. Fill the coolant reservoir until coolant comes out of the heater core hose or the heater core. Once coolant comes out, reattach the hose to the heater core... but only far enough that the hose is ON with the bleeder hole still exposed (the pipe should not cover the hole on the inside of the hose). Continue filling the reservoir until fluid comes out of the small hole. If the fluid level in the reservoir no longer drops (starts to overflow), remove the upper radiator hose from the pipe that goes to the radiator (fluid might come out of the hose). If no fluid is present, raise the hose and add fluid to the hose (filling the radiator). You might need to install the reservoir cap, to keep fluid from spilling out). Once the upper radiator hose & radiator ar full, attach it back on to the pipe. Push the heater hose on completely so that the bleed hose is covered. That should be it. Run the engine until the thermostat opens... shut the engine off and recheck the fluid level once the engine has cooled off. The quickest way to fill any cooling system.. is to use a Vacuum Fill Method. All the air is sucked out of the system (leaving a vacuum), the vacuum then draws fluid into the system.

[@DeathByHankie]

@@EXOVCDS Thanks a bunch for that thorough explanation

[@88421jake]

What would cause ticking noise when driving or reving my car its audi a4 1.9tdi b7 brb engine had full service too ? Could it be pulley or tensioner

[@EXOVCDS]

Maybe... not sure... I'd have to hear it.

[@Blaydrnnnr]

Thanks for the vid.. it was helpful, but I'm trying to diagnose an issue, where my sons 2002 Passat 1.8T had great heat, then I swapped the alternator, ( had to remove the upper radiator hose) and filled the tank, alternator fixed, but now, no heat. I tried to bled from the heater core hose bleeder hole, but never did see the fluid pour out after raising the tank full with coolant. Thought maybe I had it bled, but after starting and running to operating temp, still no heat. Came looking to see what I'm missing. As I said, GREAT heat, until I disconnected the radiator hose, so I think its air, but not sure. Bottom hose of the tank was cold, even when the gauge said 190°, upper radiator hose was hot at the clamp on top, but cool at the end at the radiator, both heater core hoses seem hot, ( actually, the drivers side was really hot, the passenger side was warm ) Think maybe it didnt bleed out all the way? Do you run the car with the tank raised, tank cap off? Or raised with tank cap on? Or does the bleed out need to be done on a cold engine? Thanks for the vid, gave me a better understanding of this thing. I'm a good mech, but these German nightmares get me messed up...

[@EXOVCDS]

I don't recall ever having to raise the coolant reservoir in order to bleed the system... it does seem to be help a lot of people (from what I have read in forums or seen on youtube). Yes, if you had heat before and are lacking now... definitely trapped air. Disconnect the heater core hose that has the bleed hole... disconnect the radiator hose at the radiator... remove the reservoir cap. Add coolant to the heater core hose (raise hose to be able to do so) until coolant runs out of the heater core or at the hose by the radiator. Reconnect whichever leaks coolant first. If coolant comes out at the radiator or hose, connect that one and continue to fill at the heater hose. If the heater core leaks coolant, attach the heater core hose (leaving the breather hole exposed) and raise the radiator hose and continue to fill. The coolant level in the reservoir will also rise as you are filling either hose.. so keep an eye on that. Once you have coolant at both ends (heater core and radiator) clamp the hoses, install the reservoir cap and see how things are. If you hear coolant rushing through the heater core when engine rpm is greater than 3000, then there's still air in the core.

[@martinee4901]

I find they need bleeding several times over several weeks. Once or twice won't do it 100%.

[@310techrepair6]

Hey bro, i have an audi A4 2009. for some reason the coolant tank is dropping coolant and i get a message saying to turn off the car and check Coolant level. at first i thought i was missing coolant but the issue was that it overheats and coolant starts getting spilled. i removed the tank and cleaned it and topped it off again but i keep getting the message to turn opff the car and check coolant. im fukn pissed off right now. any suggestions or how much it will cost to fix ? ... im getting ready to turn it in for a tesla instead.

[@EXOVCDS]

If it overheats to the point of spilling coolant from the reservoir... you're not watching the temperature gauge. Reasons for overheating: - bad water pump - stuck thermostat - broken serpentine belt (if water pump is belt driven) - broken balance shaft (that drives water pump) - bad radiator fans or fuse (only overheats at idle) You'll have to check things over till you find the cause. I can't see / tell what the problem is, from where I am.

[@SteveRobReviews]

Lots of various designs out there. WOW who can work on all brands these days.😂😂

[@EXOVCDS]

Time to get married and be a Stay-at-home Dad! =)

[@SteveRobReviews]

@@EXOVCDS Now were talking . 👍

[@osiris122cf]

Great video so i have steam coming from the return hose on top is it because my thermostat isn't opening at all ?

[@EXOVCDS]

Year, make, model, engine? What's the actual issue? Overheating? Do you have heat inside the car? Any coolant leaks?

[@osiris122cf]

@@EXOVCDS its a 1998 audi a4 1.8t

[@osiris122cf]

@@EXOVCDS no heat and it takes awhile to get it up to temp like a half hour of driving which is weird and no leaks that i can see but it is loosing it out of somewhere I'm thinking the exhaust

[@EXOVCDS]

@@osiris122cf if the engine is not overheating... the heater core is probably plugged (no heat inside) and the thermostat is stuck open (causing the engine to take long to warm up). If you don't have fluid flowing back into the reservoir, it might be because of air in the system / low coolant level.

[@osiris122cf]

@@EXOVCDS ok thank u for all your help I will try flushing the heater core tomorrow

[@SuperTralialia]

Hello if my radiator is cold is becouse of termostat ? Is closed ?

[@EXOVCDS]

Year, make, model, engine? The engine is overheating? The needle in the dash is going past the middle? Do you heat inside the car when you turn the heater on?

[@smok3sum1]

Would this cause the temp gage not to work??

[@EXOVCDS]

No.

[@youssefhassan8524]

I have the b7 Vw Passat Tai how can I bleed the system

[@EXOVCDS]

Basic cooling system filling & bleeding is similar in most vw / audi engines. The best way to do it is to use a vacuum fill method. Not having that, you simply fill the cooling reservoir until fluid no longer drops. To verify that coolant is in various parts of the system, simply disconnect a fitting to check if coolant is present. If no coolant is present, the disconnected fitting will allow air to come out and the fluid level in the reservoir will drop. Connect the hose / fitting once fluid is present. Once you are sure that enough coolant is in the system, start the engine and monitor coolant temperature via gage in the dash or scan tool. Also monitor heat from the interior heater. Air should start to get warm as the engine warms up. Make sure that the radiator fans come on and that the engine does not overheat. If coolant temperature gets too hot, shut the engine off and allow it to cool down. Check / top up coolant level once cold and then run the engine again. kzbin.info/www/bejne/gJ-3hqVmiKp9eNk

[@jaimensito1]

Hi good video, I have Audi A4 2010 is overheating.,It was a lake and then Expansion tank. I replaced it I change the coolant but still overheating , what’s can be the problem?

[@EXOVCDS]

Which engine?

[@EXOVCDS]

I can't help if you don't reply.

[@WarriyaAndPalimine]

Got some heat problems.. My lower radiator hose stays cold. I get some heat into the car but it gets colder if I drive the car hard. Temp gauge stays at 90 at all times. There is flow through the return hose if I rev the engine. AFR and engine oil temp is good. What could this be? 98 a4 b5 AEB

[@EXOVCDS]

Your car has a radiator fan that is belt driven... yes? Since there is constant air flow through the radiator, the coolant is constantly cooled. The thermostat only needs to open a little bit to allow some cooler coolant to enter the engine. The thermostat then closes again until it needs to open again. If your temperature needle were to "drop" from 90 once the car is moving at a constant speed, then I would say that the thermostat were stuck open (allowing too much cold coolant to enter). Heat that goes away with higher rpm can be caused by a bad / sliping water pump. You will need to investigate things further. Holding the throttle open with one hand (to 2500 rpm and keeping the rpm there) while eventually let you feel "warm" coolant at the radiator outlet hose... confirming that the thermostat opens / you have flow through the radiator. If the thermostat were to stay closed, the temperature gauge would go past 90.

[@WarriyaAndPalimine]

@@EXOVCDS Okay, will try this. Thank you!😁

[@trentgtxst3351]

I just replaced thermostat and I’m getting the same problem of heat being isolated at the top of the motor. Bottom pipe to the thermostat is stone cold even once my coolant temp hits 110C coolant bottle is the same…stone cold. Top pipe is hot and radiator is hot at the top corners of the entry. I get heat in the cabin but barley. It sits perfect at 90C when sitting at idle then as soon as I start driving it skyrockets to 110-120C I’m guessing the new thermostat is no good. Just pissed off I wasted $250aud on genuine g12 coolant. Is the new thermostat no good or another problem

[@EXOVCDS]

Probably an air lock / trapped air in the engine. Did you open the air bleed valve at the heater core hose when filling coolant? The air "might" work its way out by itself after a few cycles of running the engine to 110c and shutting it off. The thermostat will open and coolant might start to circulate due to convection / difference in coolant temperature. I would disconnect both heater core hoses and add coolant to the reservoir. Once coolant comes out of a hose, attach that hose back to the heater core. Hold the other hose close to the other heater core pipe.... add more coolant till fluid comes out of the other core pipe and connect the hose once the hose starts to overflow.

[@EXOVCDS]

If your main reason for replacing the thermostat was because the engine was overheating (meaning the problem was there before you replaced the thermostat)... then it could be that you have a bad water pump. Disconnect the upper radiator hose from the radiator and point it into a container. Have someone start the engine and rev-up the engine. Coolant should gush out of the upper radiator hose into the container. If no, then the water pump is bad (impeller is loose / slipping). You can check the water pump impeller by removing the thermostat and trying to turn the impeller with your finger. You should not be able to move / rotate the Impeller. Use a mirror and flashlight to look at the impeller / shaft. If it is a plastic impeller, look for small cracks around the center shaft.

[@trentgtxst3351]

@@EXOVCDS just ordered a new pump thermostat and radiator hopefully it’s not the heater core clogged. Thanks for the advice bro👍🏼 keep up the videos

[@orgrimdoomhammer2161]

hey there, i need help in form of advice :D i have a problem with my passat 1.8t, awt engine, when i drive and let foot of the throtle it leaves valves open for few sec and then i feel them close, and i see on dash 0.00 mpg, what can it be? pls help

[@EXOVCDS]

What year? Standard or automatic transmission?

[@orgrimdoomhammer2161]

@@EXOVCDS its b5.5 2001, manual 5 speed

[@EXOVCDS]

Sorry about the late reply. Clean the throttle body and perform throttle adaptation... also check clutch pedal position switch.

[@bodgitandleggitgarage]

1st BOOM

[@EXOVCDS]

Boring comment. =(

[@polecat81ath]

It been a long time from this video but I desperately want your help.I want to make an electric fan conversion to my audi aeb and Im puzzled were to put the thermoswitch in the inlet of the radiator or in the outlet @ at top hose or at the bottom.Please help.Thanks a lot.

[@EXOVCDS]

Bottom hose is outlet. All older VWs & Audi's had a rad fan switch at the bottom of the radiator close to the outlet.

[@polecat81ath]

@@EXOVCDS Thanks a lot for your answer but it confused me more.If is in outlet that mean that the temprature will be lower than exiting the engine and if the fan kick in the temp will drop instantly and power off the fan and again and again.Thanks anyway you are the best.

[@EXOVCDS]

@@polecat81ath www.passatworld.com/threads/electric-cooling-fan-conversion.321417/

[@EXOVCDS]

@@polecat81ath Better info. www.audiworld.com/tech/eng34.shtml

[@bryceb1503]

I have an issue with no heat, when facing engine does the coolant go in the left side (bleeder hole)and out the right? My right side hose is hot and I get flow out of bleeder hole but if I remove bleeder side hose I only get a trickle out of heater core and nothing out bleeder hose. Any ideas?

[@EXOVCDS]

Goes in RIGHT comes out LEFT. Your core is probably plugged.

[@bryceb1503]

@@EXOVCDS ok thank you, car was down for 2 weeks for transmission repair, had heat before but 2 weeks later not heat, thought it was strange.

[@EXOVCDS]

@@bryceb1503 Flush it in both directions with a garden hose.

[@bryceb1503]

@@EXOVCDS i will try it, thank you for all your work with the videos, its really helped me!

[@xsilata]

I apologize for the bad language (translator). I have a question - If my heating core is blocked, where will the water circulate from (before opening the thermostat)?

[@EXOVCDS]

Same way (heater core is bypassed). The engine should NOT overheat with a blocked heater core. If your engine is overheating, it is either because of a bad thermostat or bad water pump.

[@xsilata]

@@EXOVCDS If the heating core is a bypass, where does the antifreeze return to the cylinder block (before it opens the thermostat)? The pump and thermostat are new. The head gasket too. There are no exhaust gases in the cooling system (gas analyzer).

[@EXOVCDS]

@@xsilata the bypass enters next to the thermostat. What year 1.8t?

[@EXOVCDS]

@@xsilata the heater core is not "a bypass". A separate bypass is already present and constantly bypassing coolant to the water pump... that is why the heater core can get plugged without causing any issues to the engine. Once the thermostat opens, the coolant that usually goes from the head to the pump, now goes through the radiator.

[@EXOVCDS]

@@xsilata as explained in my video.

[@matej4854]

Should there be a flow of coolant with cold engine on return hose on Passat b5.5 with 1.9 tdi PD engine (year 2002, 96kw, avf engine code)

[@EXOVCDS]

I haven't checked one in a while so I can't recall if it acts the same way as the 1.8t. What's the actual problem... might be more helpful to me, so I can better guess as to what the issue might be.

[@matej4854]

@@EXOVCDS Thanks for reply. I changed the coolant in the car because it was old and now I can hear small amount of air going trought heater core especially while acccelerating and decelerating. I changed the coolant by draining it from the radiator and from block and then I slid off the hose on heater core till the bleed hole is off the nipple and then i first filled coolant in radiator hose till full and then fitted it back and then I filled expansion tank and elevated it above heater core till there was steady stream of coolant going trough the bleed hole and then while tank was still elevated I slid the hose on heater core back. Car has steady operating temperature and has plenty of heat inside. I tried heating up the car but its cold outside and i have mechanically driven fan so I cant get the lower hose hot it cooles down somewhere in the middle of the radiator. I asked should there be a flow in return line because it would help in bleeding that remained air out but i guess its the same as 1.8t. And i guess that i should heat up the car till lower radiator hose is hot too and thermostat is fully opened for some time to get flow in return hose.

[@EXOVCDS]

Yes, you just need to bleed it more... holding it at high rpm (2500 to 3000) on the highway can do it, or you just hold the RPM while the car is not moving. The thermostat is opening (even when the lower hose feels cold), it's just not open much and the constant "colder fluid" from the radiator makes it seem like there is no flow.

[@matej4854]

@@EXOVCDS I was trying to heat up the engine more but its starting to get pretty cold at my place and that mechanically driven fan cools down the coolant too fast. Coolant gets cold after first half of the radiator so i cant get the hole system hot to get thermostat fully opened for some time. But I solved the problem of remaining air which was making sound in heater core. The problem was that when i was bleeding the system the car was slightly downhill so there was always a little air left in the heater core because it was on slightly higher position than that bleeding hole on hose. After i figured that up I set the car up the way that the front was slightly uphill and then I repeated bleeding procedure and sure there was little more air that came out of the bleed hole. Now that sound is finally gone it was driving me crazy lol. And thanks a lot for answering I truly appreciate your time and effort to help me.

[@EXOVCDS]

@@matej4854 thanks for the update! I was gonna suggest some cardboard in front of the radiator or removing the Fan. Good thinking about having the front higher!

[@mousax24]

Hello i have audi a4 apu engine, i have problem air conditioner clock air conditioner with code 49 exceeds 100 temperature i replaced thermostat and tube of thermostat and 2 sensors down and down motor and also disarmed system pressure and heat still rising I have a new one because I have another poly where the thermostat rides and it still warms up

[@EXOVCDS]

Sorry, I'm not following what you are saying / have done / what the problem is.

[@mousax24]

Thomas EXOVCDS water hot to mutch

[@EXOVCDS]

Clean / wash the AC condenser and the radiator. Do you have one or two electric radiator fans?

[@Matte_Blak]

Bro my upper radiator hose gets hot, radiator fans turn on, but there’s no coolant returning. My dash temperature gauge is also acting wonky it stays on cold and the needle doesn’t move. I’ve changed the temperature sensors, water pump, thermostat, and still can’t believe it.

[@EXOVCDS]

Year, make, model, engine? I assume 1.8T? If it's a Passat, coolant doesn't return until the thermostat opens. On golf & jetta engines, coolant returns as soon as the engine is running. If the return hose is plugged, coolant can't return. If the fans come on, then the radiator must be getting hot / the thermostat is working. Do you have heat inside the car? Temperature sensor wiring or dash / gauge issue. Using a scan tool, one can communicate with the ECM & instrument cluster, to see what the temperature values are. Using a scan tool, one can also activate the gauges in the dash... to see if they sweep correctly from cold to hot, empty to full, 0 speed to max and 0 rpm to redline. If a needle doesn't move as it should, that means that the problem is in the cluster.

[@Matte_Blak]

@@EXOVCDS 2005 Audi a4, there’s no heat when I turn on heater. I’ll be sure to check it out with the scan tool thanks

[@IntradeMotors]

you forgot 1 more important thing the G12 and the big symbole of the book on the coolant bottle as that dont means to read comics. it means use vag approved coolant G13 g13++ or g12 only compatible coolant are wrong coolant if they are not meeting this spec.

[@EXOVCDS]

Yes, when car is under warranty... doesn't matter when car is 15 years old.

[@martinee4901]

I have had problems with coolant being mixed & turning into snot in a A4B5.5 2.4 that I bought, it's also got a stuck open thermostat & cracked plastic inlet hose on the heater core. On a A4B5 2.4 I have the same cracked inlet pipe & a disintegrated waterpump vanes. I 5hink anything but G12 or G13 will ruin the plastic in time, also rear coolant flange will leak. On my A4B5, the plastic legs holding the thermostat in place break & let it stay open & cold, also the heater flat motors potentialmeter resistor gets dirty ( not related)

[@martinee4901]

Sorry, plastic legs on the A4B6 thermostat, part # 06B121111D, rear coolant flange is on the 1.8 & 2.0

[@LM-gg9tg]

I think all audi a4 from b5 to b8 coolant systems flow backwards

[@EXOVCDS]

All VAG / Audi engines flow hot coolant from the engine to the upper radiator hose... and the lower radiator hose returns coolant to the engine / through the thermostat.

[@LM-gg9tg]

@@EXOVCDS that's interesting.Im a new audi owner and do many diy. Glad I came across your channel. Thank you for a very informative video.You actually SHOW and explain what's going on. I'm hooked on your channel

[@justinkremer7371]

Hey my man! I have a b5 1.8t a4. I have an overheating problem which I believe is related to the water pump. I found that the belt was very loose so I put on a new belt and it is still much too loose. Any suggestions would be greatly appreciated. Thank you.

[@EXOVCDS]

I haven't worked on one of those in a long time (water pump mounted to the side of the engine). If there is no adjustment for the belt and it does not have a split pulley (where you can remove shims from the middle to make a tighter fit around the belt), then the only option you have, is to find a belt that fits as best as possible. A little looseness is ok... the pump just freewheels along, it can't cause belt noise like power steering or the alternator.

[@justinkremer7371]

. I have seen others with this problem, but have seen no solution. So the belt only runs from w p to p s p. It does have a split pulley and the only possibility that someone else said that made sense was shims but I didn't see any. I will have to take it back apart and check. The shims would just be between the two halves of the pulley right? Other than that, I assume I would just have to find a shorter belt.

[@justinkremer7371]

@@EXOVCDS I can just turn the pulley by hand with the belt on. That would be too loose correct? I have never seen a belt this loose before.

[@EXOVCDS]

No, might not be too loose. As long as the pump turns, the belt should not slip. The PS pulley is the split pulley. Yes, if no shims are between the pulley halves, you will need to look for a shorter belt. I can't tell how loose it is from here. If you have no overheating issues, all is fine.

[@justinkremer7371]

@@EXOVCDS the water pump is the split pulley. No shims. I used a little Emory cloth to make sure everything is seating well. Seems a little better, I believe there is too much resistance on the pump probably from worn bearings. I will cross my fingers and take a test drive, but I think I will be replacing the pump.

[@TheCowgirlNiamh]

My brain hurts .... 🤔😂😂😂

[@EXOVCDS]

Take two Tylenol and call me in the morning! LOL

[@TheCowgirlNiamh]

Will do! 😉😂😂

[@ptrollan]

wait a minute here !!! you really don't need G12 coolant for my 2003 Golf with a 100k on it ? coolant light was flashing today, went to auto zone n advanced auto no G12 in stock

[@EXOVCDS]

The problem is with mixing different coolants... although, I have yet to see adverse effects. A complete flush with water and fill with universal is OK. Yes, G12/13 would be ideal... but I've seen many VW's (even boxer engines) running universal green / yellow with no issues (that I could see / detect).

[@dimitrijemladenovic9541]

Hello i did bleeding air on my 1.8t passat, and my heating worked for couple of days, but today i noticed air in system again and no heating... also sometimes my temperatue fall and come back to 90 again. could that mean thermostat is maybe bad?

[@EXOVCDS]

Could be. If the fluid level stays at the correct level, then it could be the thermostat. If the fluid level drops after a day or two, then there was still air in the system. A faulty temperature sensor can cause the needle to drop quickly and come back to normal quickly. A thermostat that is stuck open will cause temperature to drop when the car is moving and will slowly rise again once the car has stopped moving.

[@dimitrijemladenovic9541]

mine sometimes drop quickly and then rise again, not all the time just sometimes. i dont get heat, when i bleed system i get heat but still it feels like its not warm enough, i used to drive 1.9tdi passat and my heating was melting my brain :D, i bought thermostat and will change it today and if not i will try to look for other soultion like temp sensor.

[@dimitrijemladenovic9541]

@@EXOVCDS Thanks for answer, my temperature sometimes fall and come back fast, its very confusing. I will change thermostat today to see will that fix my heating problem.. also i bleed the system again and i got heat but not warm enough, i used to drive 1.9tdi passat and my heating was melting me... :D But now im freezing and its cold outside. Only good thing my heated seats work so i can kinda get warm :D, also i washed my heater core. But idk what to think anymore. i hope its thermostat or just more air in system. But how can air still get inside, maybe i didn't bleed it correctly. Can u tell me how to bleed it correctly? :D sorry for a lot of questions :D

[@PonderingOne]

I too am having problems bleeding air out and getting adequate heat. I thought the heater core was plugged but I took off the heater core inlet and outlet hoses and pushed water through the heater core in both directions. I’m looking for the complete bleeding procedure.

[@EXOVCDS]

There is no "complete" bleeding procedure. The service manual will either refer to the 2 bleed holes... one on the coolant pipe above the intake manifold and the other at one of the heater core hoses. Or it will simply say to vacuum fill the cooling system. When filling any cooling system (any engine), you have to know how much coolant came out & how much coolant the system can actualy hold, where the thermostat is, if the thermostat has a bleed hole and how the coolant in the reservoir gets to the engine. If you drained 4L and only added 2L because the fluid level is not dropping in the reservoir... then you have to think about why the coolant is not entering the engine. If opening the bleed locations doesn't help, then disconnect the upper radiator hose and fill coolant into the hose until it is full. If the radiator is empty, add coolant to the radiator and reconnect the hose. A heater core can partially be plugged and still flow coolant... making one think that the core is ok, even though it is not. Running the engine until the thermostat opens will then allow air that is trapped in the engine to return to the reservoir as pointed out in the video (no return flow until thermostat opens). Shutting the engine off and allowing the coolant to cool can also help with "bleeding", as the change in temperature promotes circulation. If the engine is not overheating, it's safe to assume that the water pump is OK, the thermostat is OK and that "enough" coolant is in the engine. A few cold to warm cycles and a few times of topping up coolant may be required to burp all of the air out of the system / into the reservoir. If there is still a problem (overheating) even after vacuum filling, verify water pump & thermostat operation.

[@karlsarkozi3626]

It's ok, Thomas. Everyone still appreciates your videos. I don't think you will be nailed to the cross because you left something out about coolant flow...

[@EXOVCDS]

I hope I won't... it is / was a big piece of info that could have saved someone a bunch of frustration. =(

[@nickosberg7290]

I have no heat both lines coming in to the heater core are cold

[@EXOVCDS]

Year, make, model, engine? When are you checking the hoses for heat? Engine cold or warm? How high does the coolant temperature needle go? Is the engine overheating?

[@nickosberg7290]

@@EXOVCDS 2004 Audi a 4 1.8 T It does not overheat the heat work sometimes Sometime the line coming in the heater core is hot and line coming out is not have heat whean i step on the gas but the other day i checked and both lines were cold coming into the heater core and the car was warmed up

[@nickosberg7290]

i flushed heater core last night seemed not to be clogged

[@EXOVCDS]

Not sure... could be an air lock in the core, but if you flushed it, at minimum it should have been full with water when you reattached the hoses. Hold the engine rpm at 3000 for 5 to 10 minutes. If you hear water rushing through the core, that's a sign that you have air in the core. Hold the rpm high until the rushing water sound stops.

[@klitoni1]

Mine acts weird, there is no flow at all to the bottle at any time

[@EXOVCDS]

As long as a cooling system is full... a plugged return hose is a non issue. If you don't have any overheating issues or lack of heat issues inside the car, it's nothing that you have to worry about right away. Sometimes the nipple at the reservoir is plugged... not the hose or the outlet at the engine.

[@klitoni1]

@@EXOVCDS Im not having issues, temp never gets above 97C(vcds) when pushing the car hard and i get good heat inside the cabin. Thank You

[@EXOVCDS]

Thanks for watching!

[@martinee4901]

Don't these run @ 89-93°C ? Mine do.

[@88421jake]

What would cause ticking noise when driving or reving my car its audi a4 1.9tdi b7 brb engine had full service too ? Could it be pulley or tensioner

[@EXOVCDS]

Maybe... not sure... I'd have to hear it.

[@88421jake]

@@EXOVCDS i will get a short video clip of the noise next time the noise happends thank

[@EXOVCDS]

Ok.