Mystery Coolant Leak - 3.0 V6 TDI

[chrisw880]

For the past 2 months, I have been experiencing a mysterious coolant leak. Took it to a local VW specialist this morning (25/07) for a pressure test which showed no external signs of a leak (engine and undertray are dry/clean), also got the car booked in at a local tuner in 2 weeks for a 2nd pressure test (08/08) to see if the specialist could have missed anything.
The specialist seems to think that there's a small chance the leak could be caused by the EGR Cooler, and the only next logical step would be to strip everything to see if that shows anything.

Has anyone on here experienced something simular and what was the cause for theirs.

Car in question is a 2008 '08' Audi A4 Quattro 3.0 V6 TDI, current mileage is 78600 and has FASH

Thanks in advance

 

[fouryoghurts]

So the pressure tests reveal zero drop in pressure?
What volume of coolant you losing over what period of time?

 

[chrisw880]

Losing about 1-1.5 litres over 5-6 weeks/~1300 miles

 

[razza1]

That's a fair amount....have you checked your water pump? The old ones had a plastic seal on them, newer ones had metal as they didn't melt...
Are you overheating as well or just having the level drop?

 

[chrisw880]

No overheating, just the level keeps dropping

 

[fouryoghurts]

If pressure test doesn't identify discrete leak and there are not signs of an external loss, perhaps you're losing it to the cylinders, i.e. head gasket's away? This can be checked with a gas analyser. Might be worth a 'stop leak' treatment...while not the best thing for your heater matrix, perhaps beats doing the head gasket...

 

[desertstorm]

I have heard of the odd EGR cooler on the older 2.5 and 3.0 V6 engines that have failed and have been the cause of water leaks but not on the newer engine.
Although they are pretty much the same design so it wouldn't be impossible for it to fail. If the EGR has been leaking they tend to be quite clean as they effectively get steam cleaned compared to a normal cooler which will have hard black carbon deposits.

Karl.