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Hi all, 1997 3.7 AEW V8 32v Sport FWD Model with 75000 miles (121000km)
Just taken my A8 on a lovely 1000km driving holiday in the wine region of my state, and of course opened her up many times and cruised at autobahn level speeds on deserted roads, and it didn't skip a beat the entire time.
5 Minutes from home coming back from the holiday the low coolant warning light came on so I pulled over and looked at the expansion tank and as you can see in the photo it was below minimum, I checked the coolant level before leaving that morning and it was slightly below max so was normal, then 300km of driving at high speed it has gone down by that much. I was so close to home and the coolant level was not critically low (still had some in the expansion tank so it wouldn't air lock) so I just drove very gently the rest of the way with no overheating problems as usual.
I had a look at the engine bay and could see coolant had sprayed out of the right side of the engine (looking from drivers seat) near the oil cooler on to the airbox as you can see in the photo, with dried coolant seen on the alternator (? from memory) and leaking down the side of the engine block on to the plastic cover. I posted in another A8 group of facebook and somebody told me the fact that it sprayed out violently on to the airbox made him think it isn't the oil cooler pipe that has let go but in fact another clamped coolant hose that is in that region probably has cracked around the clamp. I'm thinking that what happened was I did a very hard pull up to 190kph at full throttle and the pipe ruptured violently and coolant sprayed out a lot and that could explain the airbox being covered in coolant.
What's the test procedure to check if it truly is the oil cooler pipe leaking? I'm dreading taking the car apart... Does this fabled other coolant hose actually exist? Bear in mind I'm posting this to get some guidance before I begin to take the engine covers off and try and diagnose the problem myself.
Thank you all. Coolant everywhere near the exhaust manifold on the RHS The coolant level was at "max" just 300km ago Sprayed up on to the airbox!
Pressurize the system and look for the leak. I've used a big rubber stopper and blower attachment on the compressor to pump it up to 20 psi or so. Don't freak if it weaps by the water pump. Shafts meant to spin will weep under pressure while not moving.
And yes, there is a coolant line that runs from the matrix straight to the back of the engine, but it is mostly metal pipe if memory serves. Then there are the main rad hoses, the radiator core and endtanks....pressurize it to a few pounds beyond max cap rating and look, listen, smell, feel around massage hoses..
If your oil cooler plastic pipe is broken, replace it with an alloy version. Search another quattro world ish type site for "Bufkin pipe".
The coolant tank nipples break off eventually and there is a tee fitting o the left side near the firewall made of plastic waiting to break. I replaced mine with a brass barbed Tee fitting when mine burst last year with my daughters on a ski trip in the mountains.
Good luck.
Last edited by BrianC72gt; 12-06-2018 at 12:00 AM.
After some serious inspection using an inspection camera looking at the oil cooler, I decided to pull the timing belt cover off an check the water pump which revealed the culprit - my water pump has blown and coolant is leaking from the seal and was flung around inside the timing belt cover by the rotating belt spraying coolant up on to the airbox.
I'm wondering if my timing belt water pump have ever been changed, even though the previous owner assured me it was changed at 94,000km as well as it being written in the service book as being done. I'm currently at 121,000km.
Looks like I'll be organising a timing belt and water pump replacement, any shade tree ways of changing the belt without buying all the special tools and taking the front bumper off?
Front bumper comes off easy enough. You can swing the A/C condensor like a barn door and support it so you don't have to evacuate/refill that system. The work is done with #5 at TDC.
There are two bars. The 40V V8 bar is a little longer than the more common one for the 2.7T and a bunch of others. I accidentally got the wrong one years ago, locked the crank, cut the bar in half, clamped it up with a straight edge and welded in an extension. Worked perfectly. You should be able to find a cheap set for about $35 U.S., not sure what that translates to in AUSD. That said I've done belts with no tools and this one wouldn't be too bad if you just got the crank lock. You could slice the belt to half its thickness all the way around, and slide on the new belt half way from the front, then cut the old belt half off, and slide the new belt on completely. Tricky, but doable. Mark the cam cogs in relation to the block. If the belt is completely removed with no cam lock, the cog may jump forward or backward depending on valve spring pressure on cam lobes.
A 40v model can get a timing belt and water pump with the front bumper in place and no special tools, I am not sure about the 32v.. You can put the crankshaft into a safe, resting position like you do on a Porsche 928 and the RH cam won't fight you like it is wont to do at TDC. Then it's not difficult to swap belts and water pump. I made a lot of matchmarks at TDC then put the engine at 45 BTDC and made extra marks. The cams are then 22.5 degrees BTDC. It's pretty easy and very familiar to a 928 owner. After getting the belt on check the marks at TDC with the belt tight. With the special tools you do not have the issue of having to let the tensioner pull the engine into time (it pulls slack on one side of the belt and skews the timing) but if you've done a few timing belts you'd be used to this.
You do not get to do the front crank seal in this procedure since the crank is not locked. It's not ideal, the 40v has two belt tension adjusters and you want to balance the belt slack to get the cams phased just so. But the factory procedure also seems to not get the cam phasing all that great either, at least as far as the computer says. The 32v might be simpler in that regard where you just get the marks lined up (or offset to account for belt slack) and pull the pin. Preloading the belt tension with the pin still in the tensioner helps a lot if you can manage that.
12-05-2018, 05:48 PM
Is this the dreaded oil cooler pipe leak?
