Coolant leak

[Tamas]

Well I guess its my turn be lucky.....I just discovered a small coolant leak under the allraod. Cannot see anything from above, and only a tiny drop visible on the skid plate and a small puddle/leak on the concrete under it. No significant fluid loss.

Also, I have noticed this several weeks ago as well, but nothing since, and then again this morning.

I have not had a chance to take it to the mechanic or get under it really to see where it is coming from, as nothing is visible from the top. So the ultimate (perhaps idiotic) question :: Any idea where its coming from?

[A62TURBO]

Most likely the aux water pump under the manifold. http://www.audiworld.com/tech/eng69.shtml

[Tamas]

Oh bloody hell! I hope not. Is it an expensive thing to fix? Is there a quick and easy way to troubleshoot it?

[Johann2.7t]

100 bucks and a 2-3 hour diy, easy job.

[Tamas]

100 bucks and a 2-3 hour diy, easy job.

is there a very detailed writeup on how to do it? the article quoted above is good, but I dont think I could follow that one.

[A62TURBO]

is there a very detailed writeup on how to do it? the article quoted above is good, but I dont think I could follow that one.

The article I quoted is actually very detailed, I would follow it.

[Tamas]

The article I quoted is actually very detailed, I would follow it.

Ok, let me rephrase it then.....is there an idiots guide? An even more detailed version for those of us that might not be as "mechanically inclined" or are "wrench challenged"?

[blkrhyno]

I just discovered that my auxiliary pump is leaking also just order the pump and new manifold gaskets, for those of you guys that have done this did you also change the coolant switch to the blue one that come on at a lower temp or no ?

[Johann2.7t]

I just discovered that my auxiliary pump is leaking also just order the pump and new manifold gaskets, for those of you guys that have done this did you also change the coolant switch to the blue one that come on at a lower temp or no ?

I didnt but you dont have to do it all at once. I probably will down the road if i find a spare $50 hiding somewhere.

[blkrhyno]

I didnt but you dont have to do it all at once. I probably will down the road if i find a spare $50 hiding somewhere.

So changing to the low temp switch is not a bad idea

[a62.7t4ceo]

Remove the belly pan first. If it's coming from the rear of the pan, between the tranny and the engine, it's most likely form the aux pump. If it's coming from the front, it could be a couple things like the water pump or thermostat housing or hoses.

[slick50]

first thing i would look at is the valley under the intake manifold, usually when the after run is bad there is coolant pooling around it, you also can often see dried coolant on the pump itself(pink crusty crap).

[theswed86]

check the hose clamps..

[Tamas]

Well made it to the mechanic today, took off the belly pan and saw nothing.....now it might have to do with the several cm's of snow we got last night washing away the evidence on the pan, but even when they looked up from below and down around the manifold, they saw no residue at all or any sign of leaks - dry as a whistle.

So any other suggestions? How do you find an intermittent leak that doesn't leave a trace?

[Johann2.7t]

was there any fluid on the tranny? Perhaps its only activating with high temps but i could almost promise you that its your aux pump. Spend 100 bucks and rip that manifold off, worst case is that you replace and old part and get to know your car a little better.

[walky_talky20]

So any other suggestions? How do you find an intermittent leak that doesn't leave a trace?

You do a pressure test of the cooling system. Seeing as you took it to a mechanic for a coolant leak, I would hope that they did that for you. It takes only a few minutes to do. That is like the first step if the leak is not obvious. Next would be a pressure test while hot. If it leaks off the pressure, you've got problems.

[Tamas]

was there any fluid on the tranny? Perhaps its only activating with high temps but i could almost promise you that its your aux pump. Spend 100 bucks and rip that manifold off, worst case is that you replace and old part and get to know your car a little better.

Would love to do this, but the $ are super tight right now, so unless it has to be done, and the exact culprit is found, I don't have the room to experiment.

[Tamas]

You do a pressure test of the cooling system. Seeing as you took it to a mechanic for a coolant leak, I would hope that they did that for you. It takes only a few minutes to do. That is like the first step if the leak is not obvious. Next would be a pressure test while hot. If it leaks off the pressure, you've got problems.

They did both, still no dice.....it seems its the "all well in the dentist seat" scenario.

[mpower]

If the leak is in the front of the engine it could be your thermostat or water pump...

If the leak is in the back of the engine its most likely your Aux Water pump.

If you replace the aux pump (PITA, but possible without removing the intake manifold) still see coolant in the valley under the intake manifold, its the O-rings on the hard coolant pipes under the manifold. They go bad resulting in a leak that resembles the aux water pump leak since the coolant gathers in the same valley then leaks out at the back of the engine, esp when your car is parked uphill. One of the O-rings is a common failure.. its the one that goes from the front of the block into a heater core... Item 17 pg 27 in the doc below... but I'd replace all 5 O-rings on the coolant hard pipe. Intake manifold has to come out so you'll need 2 of the intake manifold gaskets as well.

Start on page 27 for diagram and 28 for part numbers needed.

http://www.vaglinks.com/Docs/Audi/B5...artNumbers.pdf

[Asicks]

Also check the coolan ttemp sensor on the passenger backside of the motor. I have replaced that o-ring twice on the A6. I would lose fluid in the form of vapor there once the motor was warm.

[Tamas]

Thanks for the detailed info guys.....I have looked again today, no sign of drips warm or cold (even overnight from last night) and I cannot see anything in the "valley" that resembles coolant ** but man, there is a lot of stuff under there

So the hunting continues....it seems it comes and goes as it sees fit

[Asicks]

Also check your coolant expansion tank...with age they can become brittle and crack......just another thing i know....but an easy thing to check ;)

[mpower]

I'd agree with Asicks.. The coolant expansion tank and related hoses/connections are the first things to check before jumping into the other items.

[Tamas]

That was the first thing I checked, there was some crud on one of the hoses, wiped it off a few months ago and nothing since.

[Siricospeed]

Well made it to the mechanic today, took off the belly pan and saw nothing.....now it might have to do with the several cm's of snow we got last night washing away the evidence on the pan, but even when they looked up from below and down around the manifold, they saw no residue at all or any sign of leaks - dry as a whistle.

So any other suggestions? How do you find an intermittent leak that doesn't leave a trace?

Cracked Coolant reservoir? Quite common. Look for crusties underneath the coolant tank. The "T" just off the front of the top hose from the tank also likes to break.

(oops, Just read the rest of the thread)