pressurised expansion bottle

[welshpete]

I have a 1995 1.8 driver with under 116k on the clock. I find that once the car has been run for a few minutes, there seems to be a lot of pressure in the expansion bottle. It don't overheat, even on a long motorway run of over 200 miles. I had it tested and it is not a faulty head gasket. I had a new thermostat housing put on it last August whilst it was in for a full service, and had the elbow replaced on the lower right hand side of the block as it was weeping.
This has me puzzled as the car uses no oil, but looses water every now and then. The oil is nice and clean, there is no sludge build up and there are no rattles or knocks when cold . Anyone have any ideas? Is this normal for a golf?

[Wayne]

Well if it is building pressure you may still have a head gasket issue.

[welshpete]

As stated, I had each cylinder pressure tested and all 4 are spot on, there is no pressure loss in them, but thanks for the suggestion.

[Deano2711]

Water pump knackered, air lock or dodgy thermostat take your pick. Is the water circulating do you know ??

[welshpete]

All the above were checked, thermostat was changed when serviced and new housing fitted, water circulating fine, system bled also, am totally stumped by this one !!

[kahunajb]

Please excuse my stupidity but isn't it supposed to pressurise once the coolant warms up?? 

If the coolant needs topping up means there is a leak somewhere which could be from numerous places i.e coolant flange, waterpump, expansion tank cap, thermostat rubber seal, head gasket etc.

[Deano2711]

Mine had an exact same fault recently. Took it to garage today and he proved head gasket was fooked. Mine has now gone in for head gasket and skimmed head, water pump and timing belt and tensioner.

[welshpete]

Think mine will have to go to different garage for the same, it may be the only way to resolve the issue. However, it does not lose power, temp. guage never reads more than the normal halfway, and it hardly  ever uses any water, and the oil is still as clean as when it was serviced!! Weird or what?

[Mr Blue]

Mine pressurised and then coolant burst out the cap. Turned out to be the small radiator pipe from the radiator to the coolant bottle that was blocked. You should have a nice flow of coolant coming out that pipe.

Put some antifreeze or dye in the coolant to make it easy to spot a leak.

My bet is on a faulty radiator and it has a small leak. Doubt its the gasket.

[Deano2711]

Mine was the same but today the garage removed the spark plugs to do compression test and plug hole 4 was a water feature !!!!!