need help with mysterious coolant leak

[bingford]

Hi, Spent the last few days under and over my 2003 Allroad trying to find the source of a coolant leak. I origanlly thougt it was an oil leak and have ruled that out. Coolant level is dropping and the leaking fluid is red and runny. I've cleaned the the underside and watched the leak. Coolant is seeping from inside the torque converter bellhousing, dripping out of one of the sdmall openings, and forming a drip at the bottom of the bellhousing. I've checked almost everything above and can't find a leaking hose, leaking coolant, resevoir, no fluid under the intake, no fluid on top of the bellhousing. There is signs of fluid at the transe temp sensor, but I've cleaned that and it's staying clean. Any ideas where my leak is? Thanks Sometimes it leaks enough to form a 12" spot on the floor, sometimes just a few drops.

[ezveedub]

Originally Posted by bingford

Hi,

Spent the last few days under and over my 2003 Allroad trying to find the source of a coolant leak. I origanlly thougt it was an oil leak and have ruled that out. Coolant level is dropping and the leaking fluid is red and runny.

I've cleaned the the underside and watched the leak. Coolant is seeping from inside the torque converter bellhousing, dripping out of one of the sdmall openings, and forming a drip at the bottom of the bellhousing. I've checked almost everything above and can't find a leaking hose, leaking coolant, resevoir, no fluid under the intake, no fluid on top of the bellhousing. There is signs of fluid at the transe temp sensor, but I've cleaned that and it's staying clean.

Any ideas where my leak is?

Thanks

Sometimes it leaks enough to form a 12" spot on the floor, sometimes just a few drops.

If it has no leaks from the upper rear coolant pipe or sensors or the heater hoses and the coolant is coming out of the bellhousing of the transmission only, then you need the rear crank seal flange. The aluminum flange corrodes though and leaks coolant. The flange is large and covers a coolant jacket section of the engine block. You'll have to take the transmission out, drain the coolant as well as the engine oil to replace this flange if it is indeed the leaking. When the flange is removed, it will dump some coolant into the oil pan and will have to clean out any sediment trapped behind the flange cover. You also need to get the turbo oil feed pipe unbolted and rotated away from the flange to get it out. It has an o-ring that should be replaced also.

http://www.ecstuning.com/Audi-All_Ro...r_Main/ES3114/

[bingford]

Originally Posted by ezveedub

If it has no leaks from the upper rear coolant pipe or sensors or the heater hoses and the coolant is coming out of the bellhousing of the transmission only, then you need the rear crank seal flange. The aluminum flange corrodes though and leaks coolant. The flange is large and covers a coolant jacket section of the engine block. You'll have to take the transmission out, drain the coolant as well as the engine oil to replace this flange if it is indeed the leaking. When the flange is removed, it will dump some coolant into the oil pan and will have to clean out any sediment trapped behind the flange cover. You also need to get the turbo oil feed pipe unbolted and rotated away from the flange to get it out. It has an o-ring that should be replaced also.

http://www.ecstuning.com/Audi-All_Ro...r_Main/ES3114/

Thanks for the reply.
Before I consider myself doomed to the above process I have to ask if there any other way for coolant to get inside the bellhousing?
Is there an opening in the bellhousing and a leak path from above that I could have missed?

Thanks again.

[ezveedub]

Originally Posted by bingford

Thanks for the reply.
Before I consider myself doomed to the above process I have to ask if there any other way for coolant to get inside the bellhousing?
Is there an opening in the bellhousing and a leak path from above that I could have missed?

Thanks again.

Not really. That's why I said to make sure there is no leaks from the coolant pipe or anything attached to it above the transmission. Also make sure there is no coolant in the V-bank of the engine where the aux coolant pump is. If you pressurize the cooling system and check everything above, but coolant is only seen coming out at the bottom of the bellhousing, then it's the flange. I've seen it leak on 2.8 and 2.7Ts way back when the cars were under warranty. It happens rarely, but it does happen.

[Prospeeder]

if its coming from the rear water manifold to head orings, they leak right on top of the trans and can look just like its coming from the bellhousing.

[k_harley]

Dont rule out the coolant bottle overflow leaking into that area. I had this happen once on an S4, so to be sure I moved the overflow tube to the driver side of the engine and then the coolant leak appeared there after a few days instead of around back of the engine / transmission. Its easy to give it a shot.