[wayne 72]

Having problems
Vauxhall Astra CDTi 2003
loosing water told it was the head gasket-replaced it
thermostat-replaced it
still loosing water
appears to be coming from coolant reservoir cap.
what could cause some much pressure, or is this a fault with the cap.
I'll be gutted, having spent £700 but just want to see an end to it.
cheers wayne

[wagolynn]

There is not a nice way to say this. The coolant cap does two jobs first it seals the system, if you look under the cap there is a seal of some sort, second it is a safety valve to release pressure should it get too high, if this is leaking then water gets lost. All in all, I would change the cap and see what happens. The other thought is, are you trying to overfill it?

[wayne 72]

hi, Im not over filling. it seems to be leaking when ive been driving for half an hour or so which was making me think increase in water temp and pressure. ive even let the water level drop in case this was causing the pressure build up.

[Rolebama]

Have you had the cap tested? They do fail occasionally.

[wayne 72]

ive replaced the cap. still loosing water. the garage say the engine block could be porous, surely this would cuase a water loss via the block, not back pressure to the expansion tank. please help

[Hometune]

Unfortinately a cracked cylinder head could cause this. You need the garage to do a proper pressure test to determine if the engine can hold pressure.

[wayne 72]

I've had the head skimmed pressure tested, head gasket replaced, and thermostat replaced. still loosing water from cap when the engine gets hot

[wagolynn]

Not sure, this is a valid test but I have used it myself and it worked. If the cooling system is functioning correctly then after the engine has cooled down, I mean cold, there should be a slight vacuum in the system. When you open the cap, you should hear an inrush of air. If you do not there is air getting in somewhere, this indicates a leak, rather than overheating due to engine malfunction.

[wayne 72]

thanks, I tried it and there was an inrush of air as you describe. I drove around for 2 hours today checking the water every half hour. the cap only started leaking after 2 hours. its got me beat.

[Hometune]

We need to go back to square one with this. Wait till engine is stone cold. Ensure water at correct level in tank. Start up with expansion tank cap OFF. Let engine idle and feel the pipes to the heater inside the car. Does one get warm quite quickly?
Now run the engine at around 2,000 revs or so and hold the radiator top hose. When the temp on the gauge shows normal/hot, the thermostat should open and the top hose get hot. Then the radiator will get hot too.
If the water in the tank starts bubbling over BEFORE this point is reached then either the thermostat is staying shut OR the water pump is not driving the water round the engine.

[wayne 72]

Ok, followed your instructions.
one heater pipe warmed up before the other.
the hose to the top of the radiator got hot. then the radiator. all before the water in the tank .
the 2 small pipes to the top of the tank are circulating water into the tank.
thanks any further advice would be appreciated

[Hometune]

Does the radiator fan come on at all? If never then suspect the cooling control module. Its behind the bumper on passenger side.

[jimmstermann]

Originally Posted by wayne 72

ok update on my Astra. Fan is working thermostat works (replaced). temp sits at 85 . garage said i had a porous block, so they used engine sealant. this has made the back pressure a lot worse. Loosing water out of the expansion tank more quickly than before. Sounds like a blockage to me and adding this solution has added to this. I could be wrong, the garage has got it back. will keep you informed. Anyones advice is welcome. thanks to everyones input and merry christmas.

sounds to me like a stupid mistake on the part of the garage that has replaced the head gasket on these 2 cars , my diagnosis is that the head gasket has been fitted upside down , this will cause one of the waterways between the block and the head to be blocked off , the car will act normally but will pressurize the water system causing coolant loss through the header tank , needs to be rectified as this can also cause hotspots within the engine leading to head gasket failiure again!!

[Frank1977]

Same here

Hi Wayne. Just wondering if you' had any luck with this as got the same problem with my van. Any help highly apreciated. Thank you.