Bubbling expansion tank

[jordeeeezy]

2001 B5 1.8. Noticed that there is some sort of bubbling occurring at the top hose in the coolant expansion tank. Just had the coolant flange replaced (thinking of going aluminum next time if it fails again). Thought that might fixed it but it didn't. Any idea as to what the reason is?

[Luis_Heineken]

Did you burb the system? the system nust have air

[jordeeeezy]

Did you burb the system? the system nust have air

I'm going to do that today. Someone in another thread said it's normal for the most part but my dad's B6 never did that. Will report back after

[$teady$upreme]

maybe just air, need to bleed it.

[jordeeeezy]

maybe just air, need to bleed it.

Yeah I'm gonna try to bleed it. Can't get enough leverage to remove the hose off the heater core without snapping it. Need to see what I can do

[$teady$upreme]

I dont you bleed it like that

[jordeeeezy]

I dont you bleed it like that

That's the only way to bleed it for the B5. There's a small hole on top of one of the hoses, start the car, pull it back until bubbles come out from the hole. Do you remove the cap when you bleed? Not really trying to lose coolant.

Did you burb the system? the system nust have air

Bled the system, still bubbling at the top hose.

[Davdraco1]

Ou don't bleed it thru the hose. You bleed it thru the expansion tank. Just leave the cap off and get the motor hot. No need to make a mess.

[B5 Gang]

Are you actively losing coolant?

[walky_talky20]

Video of said bubbling, please.

[jordeeeezy]

Ou don't bleed it thru the hose. You bleed it thru the expansion tank. Just leave the cap off and get the motor hot. No need to make a mess.

I'm pretty sure that's why the hose has a hole. For no mess. Either way, going to run a compression test and block test to see if there's any CO2.

Are you actively losing coolant?

I'm not. I thought I did because I had coolant on my driveway (obviously it has to be low). I went to work one morning and my car became warmer faster than usual. Coolant was definitely low but due to a warped flange. Swapped that out. Topped it off. No leaks found, or at least not yet.

Video of said bubbling, please.

I would but I'm going to do a block test in a bit and I want the engine cold so I can open the expansion tank before it becomes too pressurized. You can clearly see air going through the small top hose (vent hose?) of the tank. Hopefully you can visualize it

[walky_talky20]

It supposed to pump a jet of coolant through the top hose. So that's normal. But if it is constantly pumping air, that is a problem.

[Davdraco1]

I've bled my car multiple times thru the coolant tank with no issues.

[Rodgman15]

I always use the little hole on the heater core line

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[$teady$upreme]

Learn something new everyday. I always bled thru coolant reservoir too

[jordeeeezy]

It supposed to pump a jet of coolant through the top hose. So that's normal. But if it is constantly pumping air, that is a problem.

From the looks of it, it looks like small amounts of coolant is flowing through the top hose. It's not a direct stream. Going to record a video. I'll put it up by tonight. Did a compression test and numbers were consistent in all 4 chambers. Did a block test, no yellow test fluid. I ran the car for about 10 minutes to see if it would bubble and it didn't occur until I turned on the AC. Just noticed that today.

I've bled my car multiple times thru the coolant tank with no issues.

Tried bleeding it through the tank. Left it open for approximately 20 or so minutes. Still bubbled.

[jordeeeezy]

Update: just left the stealership and asked one of the mechanics what was going on. They said since it only burbles while the AC on, there must be an air pocket in the heater core or it's clogged. Since the heater core is notorious for the B5, I'm gonna blast it hopefully soon. Heater never worked since I bought the car a few years ago anyways so it's probably time. Will report back after I flush it. Thanks for everyone's help.

[elduderino200]

I'm not sure how it could continuously bubble but not lose coolant...

Either it's getting air in the system and losing coolant out the same hole, or you're still just seeing air pockets from the cooling system that need to find their way out.

[Davdraco1]

When you bleed it you always have to blast the heat, no matter how you bleed it. And I use the tank bc it's usually the highest point in the coolant system when I'm leading it. Car is usually up on ramps or stands. Hope you get it fixed. Good luck.

[jordeeeezy]

I'm not sure how it could continuously bubble but not lose coolant...

Either it's getting air in the system and losing coolant out the same hole, or you're still just seeing air pockets from the cooling system that need to find their way out.

The guys at Audi said I have air in the heater core or it's clogged. Either I'm gonna try to flush it or see if I can get the air out.

When you bleed it you always have to blast the heat, no matter how you bleed it. And I use the tank bc it's usually the highest point in the coolant system when I'm leading it. Car is usually up on ramps or stands. Hope you get it fixed. Good luck.

Lol blast the heat? I didn't know that. The guys at Audi said though about raising the car and bleed through the tank too. Gonna put the front end on ramps while on the driveway and see. I did notice a little heat when I bled through the bleed hole but it disappeared. Thanks for the info man! Appreciate it.

[Davdraco1]

You wait until the coolant is up to temp with the heat off. Then you blast the heat and it will suck the coolant they the heating system. People usually forget that and that's why they can't find the air pockets. If you blast the heat right away it will take forever to get the coolant up to temp so only do it once it is warmed up.

[walky_talky20]

I'm not certain what you guys think "blasting the heat" actually does, but I believe you may have some incorrect information. On all B5's, engine coolant flows through the heater core *at all times*. There is no shut off valve (manual or electronic) like other cars have. Even if you have the A/C blowing ice cold (or even have the HVAC completely OFF), you still have scalding hot coolant running through the heater core.

It's literally the same thing as saying "Always make sure your Radiator Fans are ON HIGH when you bleed the cooling system. If those fans aren't running, you'll NEVER get all the air out". Obviously that statement doesn't make sense, knowing the system operation. That said, running the heat is a good indicator as to whether you are getting good coolant flow through the core. But it is just that: an indicator.

[Davdraco1]

Huh. Never knew it always ran thru. Thanks for the info. All my other cars you had to have the heat on to get it to go thru that system in the car.

[Believer]

I've dumped and filled the coolant in my B5 more times than I can count. Every time the process is the same; pour the coolant in with the engine off till it stops accepting and fills up the res - usually takes a few top offs. Start the engine, let it warm up with the cap off. Wait for the level to fall, top of when it does. Cap and drive. Never had an issue, never needed to use the pin hole.

[walky_talky20]

Huh. Never knew it always ran thru. Thanks for the info. All my other cars you had to have the heat on to get it to go thru that system in the car.

Certainly. Many other cars - like Camry, Accord, Civic, Corolla, BMW's etc - shut off flow via a cable driven or motor driven valve. Audi and VW do not. Full flow all the time. Until they clog. Lol

[jordeeeezy]

I've dumped and filled the coolant in my B5 more times than I can count. Every time the process is the same; pour the coolant in with the engine off till it stops accepting and fills up the res - usually takes a few top offs. Start the engine, let it warm up with the cap off. Wait for the level to fall, top of when it does. Cap and drive. Never had an issue, never needed to use the pin hole.

I haven't flushed the system. I had the timing belt and water pump done since I didn't have the proper tools. The shop was the one that topped it off but they couldn't figure why I was getting burbles in the system (shouldn't have taken there. They need to rename Eurotech to We do BMW with basic knowledge of VW/Audi) anyways.. I tried burping the system with the cap off for aboit 45 minutes with no success.

Certainly. Many other cars - like Camry, Accord, Civic, Corolla, BMW's etc - shut off flow via a cable driven or motor driven valve. Audi and VW do not. Full flow all the time. Until they clog. Lol

The mechanics at Audi were nice enough to tell me what might be the problem. Air in the heater core (which I don't think) or clogged (highly certain) since I haven't had heat since I've purchased the car. Going to blast it out soon and I hope to clear it out.

[Believer]

I haven't flushed the system. I had the timing belt and water pump done since I didn't have the proper tools. The shop was the one that topped it off but they couldn't figure why I was getting burbles in the system (shouldn't have taken there. They need to rename Eurotech to We do BMW with basic knowledge of VW/Audi) anyways.. I tried burping the system with the cap off for aboit 45 minutes with no success.



The mechanics at Audi were nice enough to tell me what might be the problem. Air in the heater core (which I don't think) or clogged (highly certain) since I haven't had heat since I've purchased the car. Going to blast it out soon and I hope to clear it out.

Definitely sounding like the clogged core is your problem. I've heard of folks having good luck with CLR? Never used it myself.

[jordeeeezy]

I forgot to add. Anyone have tips on blasting the heater core? I've seen some people use CLR, others just run water until it's clear. I have an air compressor that I can use. I heard to use short low pressure bursts so I don't damage it.

What I suspect is that one of the previous owners used green coolant and it began to gunk up and corrode the hoses which in turn backed up into the heater core. Reason I say that is because I noticed in the tank that there is that bronzish gunk on the walls of the tank. I'm thinking of doing one of those pressurized flushes with the shop machine after I clear out the heater core.

[Believer]

... Reason I say that is because I noticed in the tank that there is that bronzish gunk on the walls of the tank. I'm thinking of doing one of those pressurized flushes with the shop machine after I clear out the heater core.

This raises a flag to me. You are absolutely correct, it could be from mixing coolants. It can also be from a failing oil-cooler, which allows oil to seep into the coolant causing the brownish sediment you see.

It could be worth your while to try and clean out that reservoir. Then, after you've filled the system with fresh coolant, you can monitor your reservoir to see if the sediment/residue returns. If it does, you may be looking at an oil-cooler replacement.

[jordeeeezy]

This raises a flag to me. You are absolutely correct, it could be from mixing coolants. It can also be from a failing oil-cooler, which allows oil to seep into the coolant causing the brownish sediment you see.

It could be worth your while to try and clean out that reservoir. Then, after you've filled the system with fresh coolant, you can monitor your reservoir to see if the sediment/residue returns. If it does, you may be looking at an oil-cooler replacement.

Damn the oil cooler too..? Haha. What're the chances of that going out? Dependent on how much and how long the wrong coolant has been used? I'm gonna read up symptoms and check how easy it is to do. I'll probably change it when I do an oil change if I need to.

I siphoned some coolant yesterday before the block test and had it settle down. Saw some gunk separate and settle at the bottom of the bottle. I'd take a picture but I'm not sure if you can really see it. The g12 is pretty cloudy.

[walky_talky20]

I used a Blast-Vac before and it worked really well:
https://www.amazon.com/OTC-6043-Blas...ords=blast+vac



Thread here:
http://www.audizine.com/forum/showth...-working-again

[jordeeeezy]

I used a Blast-Vac before and it worked really well:
https://www.amazon.com/OTC-6043-Blas...ords=blast+vac



Thread here:
http://www.audizine.com/forum/showth...-working-again

I just saw your video. Maybe Harbor Freight might have something similar. I think I'm going to try to get it done later today. You just hooked it up to a compressor and the hose?

[jordeeeezy]

Also, Ryan (Believer). A bad EGR cooler, oil cooler, or head gasket would be the only way oil could get into the cooling system right? Did some research, head gasket is good (compression test showed consistent numbers throughout). A bad EGR cooler would show milky oil and loss of coolant as well as coolant residue in the exhaust (no loss since coolant flange has been changed). Oil cooler would show milky oil (didn't see milky oil on the engine cap or on the dipstick).

Should I still change the oil cooler? The coolant is fairly new. The timing belt kit from ECS came with a gallon and I'm pretty sure the shop changed used it when they did the thermostat and water pump. I wanna say from the amount I siphoned, there was about give or take 5% of the gunk settling at the bottom.

[Believer]

In regards to the oil cooler: my experience and others from my research showed oil in the coolant reservoir in the form of brown residue/sediment in the bottom and other spots. I have not read experiences of a failing oil cooler resulting in coolant in the oil though I have seen that asserted.

I'm not saying yours is failing but just that brown residue and sediment in the coolant could be a failing oil cooler. As for replacing it, that's your call. They are not very expensive and replacing it is fairly straight forward.

Brown coolant could also just be from mixing. The tell tale is of it continues appearing in the coolant, at least in my experience. After dumping the coolant twice and continuing to see the residue building and collecting I began to suspect the cooler.



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[jordeeeezy]

In regards to the oil cooler: my experience and others from my research showed oil in the coolant reservoir in the form of brown residue/sediment in the bottom and other spots. I have not read experiences of a failing oil cooler resulting in coolant in the oil though I have seen that asserted.

I'm not saying yours is failing but just that brown residue and sediment in the coolant could be a failing oil cooler. As for replacing it, that's your call. They are not very expensive and replacing it is fairly straight forward.

Brown coolant could also just be from mixing. The tell tale is of it continues appearing in the coolant, at least in my experience. After dumping the coolant twice and continuing to see the residue building and collecting I began to suspect the cooler.



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Thanks for the info. I'll probably have it done when I'm due for an oil change.

[Woorkhorse]

Not sure how old tread is but just flushed my daughter's core flushed radiator all ready did piping on back side of motor crossover pipe ! Burped and ran car with expansion tank open and Stat opens full heat on and shut it off and blow off again !! I read in here some place that lower half of radiator gets plugged and back pressure is the culprit! I'm in the same boat ! Fyi any info would be absolutely awesome 👌

[zandrew]

Buy a burp funnel or what some call a coolant funnel. It will make bleeding coolant much easier.

The proper way is to park it flat, pull heater core hose out past bleed hole and elevate the coolant tank above the heater core hose by removing the the 3 screws that hold it in. Increase rpm and wait for the thermostat to open. Once coolant stops bubbling out and just a stream of coolant comes it's bled properly. Using the funnel makes it so much easier.