Passat coolant loss - L.Cleaver1
I had a coolant loss issue and thought I'd traced it to expansion tank and cap (when engine hot coolant coming out of top of expansion tank by the side of the closed cap and from overflow at the bottom of the tank). Now replaced both tank and cap and after 150 miles it's still happening at exactly the same places.

I've had a garage look at this and they said there are no obvious leaks.

Could there be too much pressure in the system so the expansion tank cap is (correctly) venting this through the overflow? Does anyone know where I could start looking - I'm off on holiday in about a week and going to drive about a 1000 miles so I need to get this sorted asap.

All help gratefully received.

Passat coolant loss - robcars
Did the garage that looked at it do a cooling system pressure check? It would be the obvious thing to do and possiby the only way to get correct answer?

If they didnt I suggest you get 1 done pdq. And also consider another garage if they didnt test it and tried daignosis without test.
Passat coolant loss - Hamsafar
Sounds like a possible burst head gasket - the high pressure combustion gas in the cylinder seeping into a coolant waterway and pressurising the coolant system. The cap is designed to be the weakest point to stop other parts bursting! A good garage can test the system as above and also draw off a sample of coolant and mix it with a tester that turns red if dissolved exhaust gas is present.
Passat coolant loss - L.Cleaver1
Thanks for suggestions - really helpful. Just been on a 30 mile journey - it's gone from full in the expansion tank to empty (literally as I pulled in to my house). When I take the cap off, the pressure is released and a lot of coolant flows back into the expansion tank.

There's seems to be no mixing at all of oil with the coolant in the expansion tank. The coolant itself is red so not sure if the dissolved exhaust gas test would work.

Anyone know of any good garages in the Birmingham area that could look at this (not keen on VW prices!). The car is a 99 TDi tiptronic estate.


Passat coolant loss - Big John
Check for leakage at the cambelt end of the engine (you may have to remove the cambelt cover), the water pump can fail but it is not always obvious as its driven by the cambelt, this can disguise the leak. If you suspect the water pump at all replace ASAP (+cambelt&tensioners) as if the pump fails so does the cam belt etc...
Passat coolant loss - Big John
P.S. If your carpets are wet it could be the heater matrix.
Passat coolant loss - L.Cleaver1
Carpets aren't wet - that was one of the first thoughts I had.

I'll get another garage to look at the water pump to see if it's leaking

Ask Honest John

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