Coolant Loss
 

I frequent the board often and have seen little comment about engine cooling systems. Anyone have any thoughts related to the following.


Approx. one month I got a warning indicator for low coolant level and it was indeed low - it took about 10 oz. to bring it into the proper range. Approx. 2 weeks later, same thing happened. The car is not driven hard and the temp gauge has indicated normal temps.

I've gone through the easier motions (checked for liquid on the garage floor and visually checked everything I can see without pulling shrouds and the like) and have found nothing other than another oil leak.

Anyone have any thoughts or have had a similar experience?

Check the oil cooler, there was just repairs posted recently
 

Steve Wiseman and Skiracer (AKA Doug) recently documented this coolant leak to Steve's car, and they performed the repair. Read the whole thread, there's pictures too.

Somebody else had a mechanic that thought it was coming from the water pump, but in the end, it was from the oil cooler also.

The cooler is right behind the alternator, I pulled my engine to acurately show this (man, I better hurry up and get it back in so I can pick my kids up!):

<img src="http://www.audifans.com/marketplace/images/parts/2612.A8.1.JPG">

And here's a couple of pictures from Steve and Doug's thread:

<img src="http://pictureposter.audiworld.com/24433/broken_stub_comparison_640.jpg">

<img src="http://pictureposter.audiworld.com/24433/broken_stub_annotated_640.jpg">

<img src="http://pictureposter.audiworld.com/24433/oil_cooler_back_side_640.jpg">

<img src="http://pictureposter.audiworld.com/24433/oil_cooler_attach_points_annotated.jpg"><ul><li><a href="https://forums.audiworld.com/a8/msgs/19076.phtml">Oil Cooler Coolant Leak Thread</a></li></ul>

Question to Steve Wiseman or Doug
 

This is the bottom right side of the engine, correct?

<img src="http://pictureposter.audiworld.com/24433/oil_cooler_attach_points_annotated.jpg">

If so, did you pull the RH timing belt cover? I can't believe that you did, how about the alternator, which I think you might of.

What belt do we see in the picture? Is it the timing belt or serpentine belt?

Did you remove the fan assemblies too?

Thanks. I'll have to do a close inspection next time to see if that's where my oil is leaking from, I suspect it is. Sounds like I should also replace the plastic coolant parts too if I take the cooler off.

pw

Location of Oil Cooler
 

Yes it is the front lower right side of the engine block. The part that must be removed is the Oil filter housing. This casting has the oil filter, the oil cooler (which has both oil and coolant circulating through a heat exchanger, and the mount for the alternator. To gain access, the air box, air intake ducts, the right belt cover and serpentine belt have all been removed as well as both fans. You may not need to remove the electric fan and the left belt cover for this procedure, I did. The right front belt cover was removed to get clearance to work the oil filter/oil cooler housing out of the car. You may try to get it out without removing the belt cover. Good luck. The Alternator has to be removed also. It mounts to the bracket that is part of the casting for the Oil filter/oil cooler. If you have an oil leak or coolant leak from this area, I would definately replace all the o rings, double oil gasket and plastic coolant pipe while doing the timing belt. Parts are only $26.00 from dealer (maybe $3.00 worth of parts). I don't have the invoice handy or I would give you part #s. I would lose roughly a pint of coolant per day. If the o rings are the only problem I would expect the coolant loss to be less. The short coolant pipe broke at the O ring grove on the block end of the pipe. You can see the pipe still in the oilcooler next to the new pipe I'm holding for Skiracer's photo. My leak would produce a puddle under my car. A slower leak may only make the oil pan wet or be held on the plastic cover under the engine. Driving would blow the coolant off the cover and you may never see a puddle on the drive. There are 5 hex head bolts holding the cooler to the block. 4 are easy to get to, the 5th is a bear. Use an 8mm hex socket to torque to 18 ft lbs. I found that it is easy to check if the water pump is leaking by removing the left belt cover.

Re: Question2 to PaulW, Steve Wiseman or Doug
 

Good thought but not the case however. The metal coolant pipe which brings coolant from the back of the engine has its own O ring connecting port to the oil cooler housing. There is a second exit port (short 2" plastic coolant pipe w/ O rings) to the block. If these plastic pipes start to fail, I belive a good machine shop could machine alumium pipes with the proper tolerances and O ring groves. We would want to make sure that nothing could scar the bores where the O rings seal.

Part numbers-need 2 o-rings for pipe(077 121 437), one pipe(077 117 411A),
 

one seal for oil connection(077 115 441). Dealer managed to squeeze $38 out of these parts and i didn't even address the connection at the rear of the engine.

Re: Coolant Loss
 

I would remove the beauty covers and get the car off the ground w/ ramps to gain clearance to get the lower plastic pan off. Then you should be able to see any coolant leaks. Whether from the radiator hoses or from the oil cooler. A worse case senario is a blown head gasket. I had a oil cooler leak.

Re: Coolant Loss
 

It was the undersigned unfortunate that experienced the coolant leak mistakenly diagnosed as water pump problems on my '97. The thread is authoratative, but if you are not as handy as the experts on this Forum, expect a hefty bill. I will help if you have any more specific issues, but the leak at the oil cooler acts just like a water pump fault but with the leakage dropping off the front passenger side of the oil pan. Best of luck.

Re: Part numbers-need 2 o-rings for pipe(077 121 437), one pipe(077 117 411A),
 

The metal inlet pipe and the short plastic pipe all use the same O ring. I would replaced all three O rings. as well as the oil seal and the pipe. I thought my dealer was high. What was the total w/ labor for your dealer to fix the oil cooler leak?

Paul and Steve are 100% correct, but if there is no puddle or dampness.....
 

under the passenger side of the engine, then it could be something else. Check your oil- does it look normal or is there a milky appearance? If milky, then a head gasket is the problem. 10 oz. in 2 weeks isn't very much- it could easily be leaking from the oil cooler that much and you wouldn't see a puddle. I would try crawling under the car with the lower cover off and look really carefully in the area between the block and the oil cooler for ANY signs of red coolant. Use a white rag to wipe the area down and see if there is any coolant. If you look between the oil filter canister and the alternator right next to the block, you will see a small gap between the oil cooler and the block- this is where to look. The idea of having an aluminum tube made to replace the plastic one is a good one, but we would need to be careful to get the same (or very nearly the same) alloy that the block and cooler are made from due to thermal expansion concerns. The plastic pipe is nearly an interference fit (length wise) when the engine is cool. Having these machined from aluminum shouldn't be too expensive- it is a relatively simple part. If anyone has a new plastic pipe that they can dimension for me, I can get an estimate to get some machined.