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03 A4 Quattro 1.8t Coolant Reservoir Overfloing...NEED HELP!!!

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Old 06-07-2016, 11:47 PM
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Default 03 A4 Quattro 1.8t Coolant Reservoir Overfloing...NEED HELP!!!

Alright. First let me preface this thread by letting everyone know that I have been reading other threads similar to what I am about to post, I am going to try a few solutions but I wanted to post my particular situation because my symptoms are a bit different as is the behavior of my car. With that being said here is what is going on.

I have a 2003 Audi A4 Quattro 1.8t Manual. Currently what is going on is the coolant reservoir is dumping coolant out of the pressure release valve AFTER the car builds up too much pressure. Sometimes this happens while the car is being driven, sometimes after I shut the engine off, and just tonight while trying to diagnose the issue further pressure is built during idle.

Starting with while driving:
What I have found is that I can drive my car carefully, normally, or aggressively, and it doesn't seem to have much bearing on how quickly pressure builds up. I can hear the hoses making their gargling sounds but as far as I can tell the coolant doesn't dump while driving. The temp gauge stays at operating temp (half way mark on the gauge but I don't know what temp it actually is.) while I am driving and has never hit the red line. It will move from half way mark to the 3/4 mark but goes back to half way point when I coast or pull over to idle (This does not always happen). Sometimes it takes 5 minutes to heat up, sometimes a half hour. It is always random how far/how long I can drive for. The coolant light has never come on either, the majority of when the coolant dumps is after I turn the engine off...even if temp gauge never moves from half way mark. Which leads me into when it dumps AFTER the engine is off...

When the engine turns off after driving:
As stated, after driving for X amount of time once I turn the engine off coolant will back-flow through the reservoir and out the pressure release valve. Sometimes it's immediate, sometimes it takes 5-10 minutes. Again completely random but it seems more like it happens sooner than later. This is when the most coolant is dumped and when I go to refill the reservoir back to the min/max line it takes about 1/4 to 1/2 a jug. I am using 50/50 G12 coolant right from Audi and they mix it there for me. I am having to do this almost every time I drive the car regardless of the distance, so instead I stopped driving it so I didn't risk causing any damage to the head gasket.

Diagnosis:
I spoke to the Audi dealership and 2 of the service advisers lead me to believe that the thermostat is to blame for this. Of course what they were going to charge me was more than I wanted to spend so I took the car to an Audi specialty shop and using an infra red temp sensor they also determined that the thermostat was to blame (I never told this shop that Audi had suggested it was the thermostat). How he described it to me was that the thermostat wasn't opening up to allow the coolant to efficiently flow through the engine. So because of both diagnosis's I decided to take on the thermostat, took me a while but I was successful in my endeavor. However, the same thing is happening. I bled the system both with the cap off the reservoir for 10 minutes, and with the cap on but using the bleeder valve until the coolant ran clean. The same problem still exists. So this led me to testing it idle...

Idling the car:
From completely cooled down (with the overflow cap off) it only takes about 10-15 minutes before the coolant level rises in the reservoir, starting at the min/max line and rising to just shy of where it would come out of the pressure release valve. At that point I put the cap back on before turning off the engine, after waiting over an hour for the engine to cool I rechecked the level in the reservoir and it is back to the min/max line with no coolant lost. What this means to me (assuming of course) is that the coolant isn't leaking or dumping out anywhere except for that pressure release valve in the reservoir, and only after it builds enough pressure.

Final thoughts/conclusion/suggestions.
At this point I have no idea what to do. I don't smell exhaust in the reservoir, it's not the thermostat, I haven't replaced the cap or the reservoir yet but those are 2 things suggested in the forums. I have pulled the plugs and there is no residue on them, I just changed the oil during this process and nothing was milky or any signs whatsoever that the head gasket is to blame. I also did a pressure test and it held just fine I just couldn't tell you what the PSI was at the time. With that being said here is what has been done...

This is not the first time this issue has happened, it was doing it probably 4 months ago. At that time I was sure it was the head gasket because like a noob I just listened to people talk rather than investigate or go through a process of elimination type diagnosis as I am now. I purchased everything from Audi that was required to do the head gasket, the timing belt, and water pump since I would save so much on labor doing it all at once...and the timing would have had to be done in 30,000 miles anyway. When I brought it to the shop (this shop was an Audi specialty shop as well just a different one) the tech (who was also the shop owner) informed me the head gasket wasn't cracked/damaged at all. He still did the timing and water pump but he found that the coolant flange on the back of the block was cracked/damaged and he replaced it and somehow that seemed to solve the problem. This issue hasn't happened for months now (4 months/10,000 miles?) and I have thoroughly checked that flange and no damage or leaks at all (It was also checked by the same shop that used the infra red temp sensor and suggested the thermostat be changed, so really should I trust them at this point?). The one thing I am concerned about (because I have been reading it in threads here) is the radiator's flow being blocked, apparently that has caused this issue for other people...however, it wasn't the cause the first time, and my radiator is only a year old. Maybe 50,000 miles on it tops!

So PLEASE, any help or suggestions at this point would be helpful. I do not know what my next step is except to replace the cap and/or reservoir. I of course will let everyone know if that is the issue but please, please, offer suggestions. Thank you for taking the time to read this, I know it was a novel but I wanted to be specific.

-Steven
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K Bill Adriatic (02-02-2021)
Old 06-08-2016, 01:54 PM
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Sorry to be the bearer of bad news, but I'm pretty sure your head gasket has a breach.

I was unfortunate enough a few years ago to have a Series 1(96-99) Subaru. The company managed to follow up on one of their best engines (2. 2) with one of their worst (2.5 4 cam). Famous for blowing head gaskets, which the 1.8 Audi is not, btw. On the Subie, I lost the first one at 80k, the second at 160k.

The gurgling sound is either air bubbles, or more likely, combustion products in the system. When my Outback's HG started to go, it wasn't all or nothing, the problems you are describing happened intermittently at first, sometimes with months in between. But eventually you couldn't turn the car on without it pumping up the system and blowing out coolant. The coolant flange at the back of the engine is a common failure in these cars, and may have been a cause of a leak, but that's not your problem.

The combustion over pressure causes the cap on the coolant tank to compress it's spring-loaded valve, relieving the pressure by diverting coolant out the overflow tube. The coolant tank itself has no pressure relief valve. You could try a new cap, as the current one may be gunked up. Eventually this will happen when the coolant hasn't even warmed up.

You can use a CO sniffer to test for combustion products in the coolant.

If you want, repeat the test with the cap off on a cold engine. Start it up, and look closely for little bubbles in the tank. After you turn off the engine, there will be bubbles also, but you can't see them because the system wants to blast in your face if you remove the cap.

BTW, how long have you owned the car? Has it ever overheated on you? How long after you bought it did this start happening? Perhaps the PO cooked it badly, knew what he had done, and got rid of it.

Last edited by W261w261; 06-08-2016 at 03:15 PM.
Old 06-09-2016, 03:51 AM
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I suggest you get hold of a radiator pressure tester. It's essentially a littler pump and guage. The coolant system will operate between 1-2 bar, so you park on some dry concrete, remove the plastic under tray, pump the pressure tester up To say 2.5- 3 bar, take note of the coolant level and leave it say overnight. If you have a crack in a hose or the rear flange you will have a puddle, if you loose pressure ( and coolant) but no puddle then it points to a head gasket. If no pressure loss then you rule out cracks, hoses & head gasket. At least you start removing the guessing. If you get on OK with a local mechanic you may be able to borrow the tester overnight.
Old 06-22-2016, 06:35 AM
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alright after a bunch of ripping apart and putting back together and pressure testing I found a pinhole in the overflow tank. I replaced that and the cap with it of course and it seemed to have solved my problem with it pouring out after it builds up enough pressure. However my gauge still jumps around every now and then to the 3/4 mark and then back to operating temp. One time since my last post on this did the gauge start to climb and my coolant light came on the dashboard. I pulled over and the overflow was at the min/max line, there are no indications of leaks or anything. I let the car cool for about 15 minutes and then drove it again. Coolant light has not come on since nor has my gauge jumped. So the car is running fine right now but I am still concerned with what caused that jump and indicator to come on.
Old 06-23-2016, 07:59 AM
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How about the gurgling, which indicates air in the system? If an air bubble goes by the temp sensor you can get a needle jump as you described.

I doubt a pinhole leak would result in fluid "pouring" out. IfIf things have calmed down, more likely the new radiator cap was the solution.
Old 06-23-2016, 08:16 AM
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I'm going to guess that you had air in the system due to the coolant leak. That can cause the gauge to do what you described. In the future if you are worried about a head gasket leak use this:

https://www.amazon.com/UVIEW-560000-...rds=block+test
Old 06-24-2016, 06:55 AM
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After bleeding it forever the gargling went away, according to Audi the pinhole in the tank was letting air go in the system and the was causing it to flow out once pressure built up. I asked if the cap could be the issue instead of the tank and they replied by saying since the tank has a hole in it, even if the cap was bad the hole would still cause an issue. I was already annoyed at what's been happening, I replaced the tank and again bled the system, no leaks, no gurgling, and outside of that one event I just mentioned above my car has been treating me well. Making some new sounds and my wipers for some reason don't move or work now but at least the coolant issue seems to be solved.
Old 09-27-2020, 09:50 PM
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Default Coolant leak through the release valve

Originally Posted by Kryptoknight
Alright. First let me preface this thread by letting everyone know that I have been reading other threads similar to what I am about to post, I am going to try a few solutions but I wanted to post my particular situation because my symptoms are a bit different as is the behavior of my car. With that being said here is what is going on.

I have a 2003 Audi A4 Quattro 1.8t Manual. Currently what is going on is the coolant reservoir is dumping coolant out of the pressure release valve AFTER the car builds up too much pressure. Sometimes this happens while the car is being driven, sometimes after I shut the engine off, and just tonight while trying to diagnose the issue further pressure is built during idle.

Starting with while driving:
What I have found is that I can drive my car carefully, normally, or aggressively, and it doesn't seem to have much bearing on how quickly pressure builds up. I can hear the hoses making their gargling sounds but as far as I can tell the coolant doesn't dump while driving. The temp gauge stays at operating temp (half way mark on the gauge but I don't know what temp it actually is.) while I am driving and has never hit the red line. It will move from half way mark to the 3/4 mark but goes back to half way point when I coast or pull over to idle (This does not always happen). Sometimes it takes 5 minutes to heat up, sometimes a half hour. It is always random how far/how long I can drive for. The coolant light has never come on either, the majority of when the coolant dumps is after I turn the engine off...even if temp gauge never moves from half way mark. Which leads me into when it dumps AFTER the engine is off...

When the engine turns off after driving:
As stated, after driving for X amount of time once I turn the engine off coolant will back-flow through the reservoir and out the pressure release valve. Sometimes it's immediate, sometimes it takes 5-10 minutes. Again completely random but it seems more like it happens sooner than later. This is when the most coolant is dumped and when I go to refill the reservoir back to the min/max line it takes about 1/4 to 1/2 a jug. I am using 50/50 G12 coolant right from Audi and they mix it there for me. I am having to do this almost every time I drive the car regardless of the distance, so instead I stopped driving it so I didn't risk causing any damage to the head gasket.

Diagnosis:
I spoke to the Audi dealership and 2 of the service advisers lead me to believe that the thermostat is to blame for this. Of course what they were going to charge me was more than I wanted to spend so I took the car to an Audi specialty shop and using an infra red temp sensor they also determined that the thermostat was to blame (I never told this shop that Audi had suggested it was the thermostat). How he described it to me was that the thermostat wasn't opening up to allow the coolant to efficiently flow through the engine. So because of both diagnosis's I decided to take on the thermostat, took me a while but I was successful in my endeavor. However, the same thing is happening. I bled the system both with the cap off the reservoir for 10 minutes, and with the cap on but using the bleeder valve until the coolant ran clean. The same problem still exists. So this led me to testing it idle...

Idling the car:
From completely cooled down (with the overflow cap off) it only takes about 10-15 minutes before the coolant level rises in the reservoir, starting at the min/max line and rising to just shy of where it would come out of the pressure release valve. At that point I put the cap back on before turning off the engine, after waiting over an hour for the engine to cool I rechecked the level in the reservoir and it is back to the min/max line with no coolant lost. What this means to me (assuming of course) is that the coolant isn't leaking or dumping out anywhere except for that pressure release valve in the reservoir, and only after it builds enough pressure.

Final thoughts/conclusion/suggestions.
At this point I have no idea what to do. I don't smell exhaust in the reservoir, it's not the thermostat, I haven't replaced the cap or the reservoir yet but those are 2 things suggested in the forums. I have pulled the plugs and there is no residue on them, I just changed the oil during this process and nothing was milky or any signs whatsoever that the head gasket is to blame. I also did a pressure test and it held just fine I just couldn't tell you what the PSI was at the time. With that being said here is what has been done...

This is not the first time this issue has happened, it was doing it probably 4 months ago. At that time I was sure it was the head gasket because like a noob I just listened to people talk rather than investigate or go through a process of elimination type diagnosis as I am now. I purchased everything from Audi that was required to do the head gasket, the timing belt, and water pump since I would save so much on labor doing it all at once...and the timing would have had to be done in 30,000 miles anyway. When I brought it to the shop (this shop was an Audi specialty shop as well just a different one) the tech (who was also the shop owner) informed me the head gasket wasn't cracked/damaged at all. He still did the timing and water pump but he found that the coolant flange on the back of the block was cracked/damaged and he replaced it and somehow that seemed to solve the problem. This issue hasn't happened for months now (4 months/10,000 miles?) and I have thoroughly checked that flange and no damage or leaks at all (It was also checked by the same shop that used the infra red temp sensor and suggested the thermostat be changed, so really should I trust them at this point?). The one thing I am concerned about (because I have been reading it in threads here) is the radiator's flow being blocked, apparently that has caused this issue for other people...however, it wasn't the cause the first time, and my radiator is only a year old. Maybe 50,000 miles on it tops!

So PLEASE, any help or suggestions at this point would be helpful. I do not know what my next step is except to replace the cap and/or reservoir. I of course will let everyone know if that is the issue but please, please, offer suggestions. Thank you for taking the time to read this, I know it was a novel but I wanted to be specific.

-Steven
I have this same problem on my Audi A4 1.8T 2004 Model.I can drive for some hours but when you turn off the engine coolant comes through the release valve
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