Long Term Coolant Loss
 

Had the 1.8T for nearly six years now. When I got it it had done 38,500mls and was using about a cup full of coolant every month. Could not see any external leaks so decided to do the head gasket. Fitted new head gasket (BW750) belts & water pump. Whilst the head was off I checked liner heights which were just proud of the block. 50,000mls later and it still uses about a cup full of coolant a month.

Over the years I have replaced all the rubber hoses and connections. Last year I fitted a VVC manifold. Still uses a cup full a month. Only seems to loose coolant after a series of short trips.

Yesterday after buying a pressure test kit I pumped the cooling system up to 20psi and after half an hour it had dropped to 15psi. After removing the pressure test equipment the coolant was low as you would expect as it had been pushed out somewhere. I could see no external leaks. Where the heck is it going? When I started the car it ran perfectly as it always does. If the coolant had been pushed past the head gasket or VVC manifold I would of expected it to run lumpy for a couple of minutes but it didn't. Anybody hazard a guess where it is going? I've had the bumper off in the past (several times) and can't see any leaks from the radiator.

Regards John

Water pump?
Just because you didn't mention it.

Maybe try some fluorescent dye and a UV torch. It can be handy for locating an external leak when all else fails.

http://i5.photobucket.com/albums/y19...ps2ac75286.jpg


TC

Yes, forgot to mention I did put a new water pump on at the time but that is now 50,000mls old. Fluorescent dye is a good idea. It does (to me) have all the hall markings of a failing water pump. When I fitted it I did not apply any RTV sealant just relied on the supplied O ring. I have read a few posts about using RTV as well.

Regards John

Are you checking the level with the vehicle level and when cold? Are you using the correct "Max" level ( it is at the bottom of the part of the header tank that you can see)? Have you replaced the header tank cap or seals? (they are prone to leaks)
:shrug:
All worth checking before you suspect hgf problems.
Mike

It could also go into the oil. At least in theory.
A small amount like that would be burnt off and would not cause any visible mayonnaise to be formed.

If you suspect the coolant is getting into the engine oil, there's a rather neat test you can do. Maybe worth trying.

The test involves placing a couple of drops of used oil on blotting paper, filter paper or even the back of a business card. The paper is left to stand for a few hours during which the lube oil will migrate outwards in a ring. If a dark or brownish stain is left in the center after the oil moves outwards, then this could be due to failing oil dispersancy and soot coagulation. This is a common effect of glycol contamination. A black sticky paste with a well-defined edge is cause for concern. Very often a soot ring develops around a yellow/brown center when glycol is present.

TC

Yes I am checking the level when cold and only fill it to the max level at the bottom of the tank. Over the years I have had six new caps and a new header tank. Still looses coolant. Also before I did the pressure test coolant was sitting on the max level but afterwards it was not even on the minimum. Took a good cup full to bring it up to the low level.

I don't think it is going into the oil as the level never rises and it is not milky at all.

Regards John

Are you getting any coolant smells/leaks from the heater matrix/hoses in the cabin area (often smells a bit like curry-strangely!)? The heat will often evaporate the coolant but leaves a stain on the carpets/in the area of loss.

No smells inside the car. I am going to whip the timing belt cover off to have a look at the water pump to see if that is leaking.

Regards John