Audi A8 This full sized Audi A8 sedan offers interior luxury and spaciousness comparable to any car in the full sized luxury sedan class

A8 mystery coolant leak

  #1  
Old 10-19-2012, 11:05 PM
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Default A8 mystery coolant leak

1999 A8...I recently put a new timing belt & water pump on. mostly because I bought the car with 198,000 miles and there was no record of timing belt change. thought the water pump was bad because it made this clearly audible bad water pump rattle. turned out to be the fan clutch. the next day I had a puddle of coolant under the car. day after day, it wouldn't leak when running, but after cooling off for 6 or 8 hours a little coolant would leak on the floor. the drip would come from the bottom of the engine, just behind the timing belt cover. I tore it down assuming it was the water pump gasket that hadn't taken. found the water pump bolts pretty loose, so I torqued them down about double what the procedure on this web site says. put it back together. still had the little annoying leak. after reading up on possibilities, settled on the leak must be coming from the oil cooler. the oil cooler has coolant passing through it to cool the oil. the oil cooler is the oil filter housing and alternator bracket all in one. there is a little plastic tube that carries coolant from the block to the oil cooler. it's about 1.5" long and 3/4" diameter. a plastic tube, which breaks off on both ends, besides the o-rings rotting off. why they did this instead of using an aluminum one is an error one doesn't expect on such a vehicle. I found a guy on ebay who makes and sells aluminum replacement tubes with double the o-rings. pricey at $27 but well worth it. plus you have to buy the fancy figure 8 gasket which isn't cheap. how to do the job is posted here: audipages A8 Oil Cooler Removal and Reinstall . the job isn't near as bad as they make it out to be. the hardest part was the turning it this way and that to get it out and back in. put it back together and no more leak. cost about $60 in parts. I highly recommend the aluminum tube...
 
  #2  
Old 10-19-2012, 11:30 PM
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Default A8 oil, vacuum & coolant leaks 1998

I bought a 1998 A8 about a year and a half ago. typical of a 100,000 mile+ car the first thing you have to do when you get it home is tear down the back of the engine. what I mean is you take off the plastic engine covers, along with the throttle body and intake elbow. there are vacuum, coolant and crankcase vent tubes on the back of the motor that will need to be refreshed. there is a bundle of vacuum lines that appear to be brake related. if your lucky they will be in good shape. if not it might cost you a lot to replace them. or maybe a clever person can rig them up home style. I like factory fit. I found a rip on a little Y elbow piece. I managed to clean it up good with electrical cleaner, and then mend it with black silicone. worked better than I thought it would. a metal coolant pipe goes from one side of the block to the other. replace the o-rings on each side. the crankcase vent tubes are big and tend to flatten out. replace them if you have the money. check and replace other vacuum lines as needed. then for desert, replace the output shaft gasket on the transmission. these things are not difficult. they just take some time. I love working on these cars because they are worth working on. up here in Maine. an aluminum body that never rusts and 4-wheel drive go a long way. We have two of them. a 98 and a 99. 300 horse V8, very quiet and comfortable. very well built. 4100 lbs when it's made of aluminum means there a lot of car in there. I do my own work, so I can afford to fix them. For the reputation they have, they really aren't difficult to work on. by the way, I forgot to mention most likely you'll have to replace the power steering lines and transmission lines. these 2 sets of lines are the cars major weakness. they rust quite badly, and aren't cheap. awesome cars.
 
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