Coolant leak

[lswing]

I've searched through threads but have not found much info on the problem. Basically loosing about a quart of coolant a week, started a few weeks back and seems to be getting worse each day. Going to the mechanic in a few days. The car had some coolant hoses replaced last year and has been fine until now.

Any primary/common place to look around on the car for the leak? I know it could be a lot of things from a hose to a head gasket.

Thanks.

[hahnmgh63]

Start with what the mechanic replaced. Why did he replace them? Just age?

[lswing]

Serviced for coolant leak about 10 months ago by previous owner. Been good since. Says they replaced the left and right hoses. Hopefully just a loose clamp, will update.

[SteveKen]

Do you have the aux radiators? try looking at all the plumbing to and from them.

The banjo fittings at the supply and drain lines at the turbos.

The infamous plastic oil cooler manifold pipe.

Good luck.

[lswing]

Great, thanks for the info! The radiator setup is stock, as far as I can tell....

[Spidercat]

Good luck! Hope it's something simple. If it is the oil cooler plastic pipe, James Bufkin at Bufkin Engineering makes a nice aluminum replacement with viton o-rings for $25 including shipping. I had mine by the end of the week. Great guy to deal with.

See this thread:
http://www.rs6.com/showthread.php/22676-Plastic-coolant-pipe-replacement?highlight=coolant

BTW, it's still sitting in the glove box. Changing it requires an engine pull which isn't covered under fidelity gold-plus (only platinum) so I'm making do until either the engine has to come out for another reason, or until this gets to be more than a few drips per day. I just wanted it to be ready when needed.

[kismetcapitan]

could also be the coolant recirc valve, which is also made out of amazing plastic...mine's got a slow leak, can't see it due to the engine bottom tray, and I'm losing about half a quart a month.

[hahnmgh63]

I think the oil cooler plastic pipe could be done without pulling the engine. The oil cooler is right in front of the start and I can't say for sure until I get my engine back in but from the looks of it it could be done much easier than pulling the engine. There are 5 bolts holding the cooler assembly on and the plastic pipe (3" long) mounts from the back of the cooler to the engine block. I replaced mine with the Bufkin piece and it is a real nice piece with double o-rings. My plastic original pipe was still very strong so I would think that possibly cars from the warmer climates would have more of a problem with heat soak causing the plastic pipe to get brittle. But if you have a leak or have your engine out there is no reason not to replace it.

[SteveKen]

I've done it on my S6 without an engine pull and it as super difficult.

I had the engine out of the RS6 when I did it. I would say it can be done with the engine in place, but would be damn near impossible without some home made tools to access the PITA low height socket head cap screws that strip just by looking at them.

[Elevens]

Loosing about a Quart a week with no visible signs of leaking doesn't seem possible. When was the Timing Belt done? Since I assume this would include a Water Pump Replacement. But if there is no visible leaking then its not likely a Water Pump. But who knows. Just my thoughts....

[na1mt]

Check your engine oil for signs of coolant

[bmlee007]

I had to replace a hose that went from the block to the throttle body. I was losing fluid slowly, a lot less than you are, but still a pain. However, I knew the general area because it was always burning off of the header when it happened. Also look in the tray under the coolant expansion tank, maybe you have a bad o-ring on the cap and pressure is pushing fluid out slowly. There is a nipple pointing down under the cap area for overflow, if you feel any at the end of the nipple, replace the cap. That was my first step, which worked, until the aforementioned hose let go.

[4everRS]

I agree. This sounds odd. If your not seeing fluid on the ground after this size of loss, it doesn't sound very good.
Check your engine oil for signs of coolant

[lswing]

Timing belt was done about a year ago, water pump also I believe. It has been raining a bunch here, making it tough to notice a leak. It did seem close to a quart to me though, although that may have been over two weeks, I'm now monitoring it closer. At first I thought it was just low, but I now know there is a leak somewhere. In with my mech all Thursday, I'll let you all know. Thanks for the ideas on what to look for.

[lswing]

So either I'm really forgetting things, or the level went back up by a quart today. Same location for checking, would temp matter that much? Is something not returning all fluid to the tank, possible?

[na1mt]

A simple pressure test of the coolant system should narrow down or rule or confirm the simple probabilities.

[lswing]

It's the water cooler behind the drivers side intercooler, didn't even know that was there. Any advice while we're down there? Looking at the Wagner kit since we're in there, but is a good amount of $$. Another other repair pointers? Probably going to order the stock water cooler, will be $300 for the part. Thanks!

[MaxRS6]

Might consider the water cooler behind the passenger side while at it. Maybe they'll provide a quantity discount. I did both of those and the front radiator at one time along with the various hoses. Just make sure they route all the hoses properly back into place so they don't become sliced by a pulley while at a track event as I heard someone else experience..00

[lswing]

Thanks Max. I just remembered, been hearing about eliminating the secondary radiators, I'll search threads, but does anybody want to chime in?

[1 bad 03 rs6]

Yeah, I took out the aux rads. when I did the timing belt and water pump. Not sure they are worth keeping even in a hot climate as the will heat soak the inter"coolers". More of an afterthought by Audi for the North American units in my opinion. Taking them out allows air to flow through the IC's instead of slowing down hitting a wall of heat. I bet it's worth a bit on the power side too. If spraying the IC's helps, I would think this would help a little as well. My 0.02

There are a couple of threads on here with pictures if you do a search.

(I know some may disagree with me, but I did not install the fog lights in the new bumper cover for the same reason. Airflow to the IC's. The fog lights are right in front of the most direct path to the IC's.)