[cosimo]

I have a very strange coolant leak, that my mechancis have not figured out yet. It leaks a "puddle" in the garage after driving it and it cools off. Checked hoses, replaced water pump gasket, did pressure test after and it passed. It seems to be coming front the right front. Going to take it make to IMA but I thought maybe one of you tech gurus would have an idea on what the problem is.

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[banditsc]

In the right front you have the lower rad hose, the thermostat housing, the heater control valve, I suppose the water pump could look like right front also. What are the age of these parts?

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[flash]

i'm betting heater control valve - i had one do that - would seep a bit, but only at certain temps - tiny puddle, but no signs of leakage anywhere else

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[Renalicious]

There are a couple coolant leaks that I've had in the past (well one of them I have right now). First one happened right after I had the whole front end serviced 2 years ago, and there was a bad clamp on one of the hoses. When the car was first started and the system pressurized, the coolant started leaking. Then once everything got up to temp and materials began expanding, the clamp would tighten up and stop the leak.



Currently I too have a leak that is a bit mysterious too, but it looks like over pressurization when the car is cooling down. Basically I think my thermostat is telling the fans to kick in too late, and the coolant in effect boils over for a few seconds. This can happen while the car is running and sitting in traffic, or after I shut it down and there is no more circulation. I'm going to ask the shop if they can put in a new thermostat with a lower threshold and see if that helps at all.



And yes, if you haven't replaced the heater control valve, do so now. When it goes, its GONE. Save yourself the headache and do it the next time you're at the shop.

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[banditsc]

[quote name='Renalicious' post='47757' date='Feb 19 2008, 11:00 AM']There are a couple coolant leaks that I've had in the past (well one of them I have right now). First one happened right after I had the whole front end serviced 2 years ago, and there was a bad clamp on one of the hoses. When the car was first started and the system pressurized, the coolant started leaking. Then once everything got up to temp and materials began expanding, the clamp would tighten up and stop the leak.



Currently I too have a leak that is a bit mysterious too, but it looks like over pressurization when the car is cooling down. Basically I think my thermostat is telling the fans to kick in too late, and the coolant in effect boils over for a few seconds. This can happen while the car is running and sitting in traffic, or after I shut it down and there is no more circulation. I'm going to ask the shop if they can put in a new thermostat with a lower threshold and see if that helps at all.



And yes, if you haven't replaced the heater control valve, do so now. When it goes, its GONE. Save yourself the headache and do it the next time you're at the shop.[/quote]







@ Renalicious



Have you installed a lower temp thermo switch yet?

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[Renalicious]

Nope, but I have heard a lot of people on this forum talk about it though. I'm hesitant to do so incase there is a much more serious problem lurking <img src="/forum/images/smilies/968/mellow.gif" class="smilie" alt="" />

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[cosimo]

Have not replaced heater control valve. Water pump and lower temp thermostat have been replaced. I will suggest the HCV as I have heard they are notorious for going bad. The amount of coolant is not a tiny puddle but is big enough to flow out the side of the car. I believe there is an Audi part made of metal. Is that part still available?

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[flash]

also, when you get in there, make sure you are running a phosphate free coolant and de-ionozed or purified water - these radiators are also notorious for blocking due to deposits from the coolant and water



by the way, everybody should be doing a complete coolant flush at least every 2 years

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[94SilverCab]

Cosimo,



Pete has reccomended the OEM HCV over the Audi one because the internal valve is different. (Shutter valve vs. butterfly). I understand that folks have successfully used both. The Audi one is available from Autozone...some are all metal, others have plastic internals, my understanding is that it is the same part # so you don't know which it is until you see it.



Jay

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[cosimo]

Thanks, Jay. I did a search on HCV and read the comments including Pete's. It seems both camps have had success. My only thoughts were 1) why does it happened only when the engine cools off and 2) it is headed for a catatrospic failure? i.e. can I drive the car?

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[flash]

because of the material, there is no telling how long it will continue the way it is - like said above, when it goes, it will go completely, leaving you stranded



$25 part - 1 hour tops to install

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[Chris Vais]

I have experienced some of the leaks mentioned above and one which hasn't. There is a drain valve at the bottom of the radiator, left hand side I believe, that was leaking on my car. I had a small pool of coolant on the garage floor every day that I used the car. This valve is rather fragile, being made of plastic, it has a tendancy to break if you mess with it. My advice is don't mess with it without having a replacement on hand. I have also learned that in some cases the fluid I see accumulate on the garage floor isn't always directly below the source of the leak. I didn't identify the valve as a leak source until I removed the lower engine shroud and ran the car without it in place. The source of the leak became more obvious.

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[Mark]

Cosimo- I'll bring one of my extra HCVs for you on Saturday. Only PITA about changing it is (at least from what I remember when one of mine let go) is you have to remove the oil filter to get to the HCV.

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[Darryl]

[quote name='Mark' post='47780' date='Feb 19 2008, 04:05 PM']Cosimo- I'll bring one of my extra HCVs for you on Saturday. Only PITA about changing it is (at least from what I remember when one of mine let go) is you have to remove the oil filter to get to the HCV.[/quote]



Although I don't have an extra HCV, I was going to suggest the same thing...I'm sure between the frou or five of us, we can sure manage an HCV swap!



I had to replace the smaller of the 2 connecting hoses when I did mine but I don't recall if I had the oil filter off or not. I don't think I did, but you definitely have to get the power steering resevoir out of the way.



- Darryl

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[flash]

and PULEEEEASE make sure that thing gets put back in the right spot, and not in the upper location - that dent sucks

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[cosimo]

Flash, no problem with the power steering reservoir. I already have a mark on my hood from a previous misktake by a mechanic. Mark, thanks for your consideration. What do you need from me?

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[Mark]

I need you to make the forecast I just heard for friday/saturday go away. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" /> I have 3 or 4 HCVs between the spare in each car and whatever is in the cabinet.

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[flash]

ugh - way too many (including myself) have done that - easy to do

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[RS Barn]

When we replace the HCV's the old hoses are usually swollen and don't fit tight on the ne HCV. The new OE hoses appear too short and require some stretching - clamping , cussing. We've seen these clamps loosen after replacement -heat expansion etc.

There is also a hose at back of heat tube over exhaust manifold that can leak.

Actually there is way too many places we see that leak over time.

Pete

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[flash]

that tears it - i'm working out the relocation mod

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