Mystery Coolant Loss

**yetikev** · 26-01-2009,09:14 AM

I have a 2002 1.9 TDI (130) A4 Quattro Avant, that is losing a lot of coolant, but only when the engine is under load. For example, I managed to cruise 200 miles on the motorway at constant revs (<2.5K) and lost virtually no coolant, but it will take the header tank to below minimum in less than 10 minutes of proper driving on A-roads (i.e. where there is regular progression through the gears and variability in revs).

Four seperate garages have now investigated this, with non of them finding it. All did leak tracing, pressure tests, hydrocarbon tests.

The first changed the header tank and cap as they thought it was being over-pressurised and leaking from them.

The second vaccummed out the system as they thought it may be an airlock.

The third did nothing.

The fouth changed the water pump.

Non of these remedies have changed anything, nor has an application of K-Seal (last resort to see if cylinder or head gasket).

Pretty sure it is not the head gasket, as no gunk in oil.

Any other suggestions? I cannot keep paying for garages to not fix it!!

Thanks in advance.

Kev

**zollaf** · 26-01-2009,09:39 AM

my money would be on the head gasket. i presume by hydrocarbon test you mean the blue liquid in the tube in the header tank, that changes to yellow. these dont work well with diesels.k seal wont seal a hole thats got too much pressure behind it, as it gets blown out. if theres no leak from radiator or any where else, and youve done the water pump, and its not the heater matrix, what else can it be ? any one else got any suggestions?

**yetikev** · 27-01-2009,01:32 PM

With the volume of coolant that is 'disappearing', if it was the head gasket would it not manifest as gunk in the oil or would the oil level not increase?

When I said garage three did nothing, they did an exhaustive check of the heater matrix to check for a pinhole leak or something similar, with nothing found.

All four garages seem confident it is not the head gasket, but cannot offer any other explaination. Thanks for your reponse ... Any other ideas? Has anyone else experienced anything like this before?

Kev

**nskeates** · 27-01-2009,04:39 PM

has the expansion tank got an overflow pipe ? if so it might be worth checking its not coming out of there on a hard run ? I know it shouldn't but the coolant has to be going somewhere

**jastimongo** · 27-01-2009,04:59 PM

Try taking the plastic cover off the top of the engine. Running diagonal to the camcover is a pipe with an allen key stopper in it. Nearly everyone Ive seen has coolant leaking from it. You cant see it when the cover is on. Tighten it up, maybe its that.

**yetikev** · 28-01-2009,06:49 PM

No sign of leakage under the engine cover either ... the mystery thickens!

**randall977** · 28-01-2009,08:14 PM

I've had a 1.9 TDi PD115 Passat and Golf and the head gaskets went on both - one at 36K, the other at 80K. There was no overheating, no white stuff in the oil and no sign of coolant leaking. I was fairly sure it was the HG so took it to VW and they did all the tests and said it was fine - I got them to do it again and they found it had gone. The hole must have been so small that it allowed a coolant loss without many other side effects. One thing I did notice was very tiny black specs in the header (almost undetectable) - the coolant should be absolutely uncontaminated and clear. Hopefully your HG is fine but it is a weakness on these fantastic engines. The cost isn't too excessive and it's an opportunity to get the cam belt and water pump done - cost me around £450 at a VW garage.

The Golf was fine upto 80mph then lost a lot of coolant over that!

**jastimongo** · 28-01-2009,08:25 PM

Last chance saloon!!........the header tanks are prone to cracking and in this weather expansion and contraction is greater than normal. If it is cracked at the rear against the bulk head the coolant will be leaking down the back and you wont see it as it will be dissappearing under the car.
Cant remember if you said you had a decent pressure check, but if not then its a must.

**hongkongstuey** · 16-02-2009,11:35 AM

Originally Posted by randall977

I've had a 1.9 TDi PD115 Passat and Golf and the head gaskets went on both - one at 36K, the other at 80K. There was no overheating, no white stuff in the oil and no sign of coolant leaking. I was fairly sure it was the HG so took it to VW and they did all the tests and said it was fine - I got them to do it again and they found it had gone. The hole must have been so small that it allowed a coolant loss without many other side effects. One thing I did notice was very tiny black specs in the header (almost undetectable) - the coolant should be absolutely uncontaminated and clear. Hopefully your HG is fine but it is a weakness on these fantastic engines. The cost isn't too excessive and it's an opportunity to get the cam belt and water pump done - cost me around £450 at a VW garage.

The Golf was fine upto 80mph then lost a lot of coolant over that!

i have tiny black specs in mine too, just thought it was years of dirt build up etc but you have mne worried now, im gonna ring the garage and see what they say now, they arent the sort of people to con me out of hundreds of pounds cos doing hg will take up a lot of room in their garage and they wont have the usual turn around of cars. my coolant is pink and no traces of any crap in it, but their was a petrolly sheen on the coolant when i replaced water pipe and coolant came out. running higher boost than standard so i guess it has found a way to leak.