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[Albus Dumbledore]

Does pressure in the cooling system suggest head gasket failure?

The top and bottom hoses from the rad. are rock hard, but if I take the filler cap from the eks. tank off, the pressure is released and the hoses easy again. Put the cap back on, and pressure slowly builds up again. Also see som sort of smoke/steam from the eks. tank (with cap off). Exhast is grey/hvite.
I've heard it's definite HG if the exhaust is white, but I don't know how white it should be, or how much  

[shyboy]

Have you sorted the blockages in your cooling system yet? Whilst a failed HG will cause pressurisation of the cooling system, couldn't it be associated with your restricted water flow if it still isn't clear.
A failed HG would almost certainly cause rough running. Is this the case?
White 'smoke', (not light blue and with a smell of oil), is normally water condensation, which is a normal product of the combustion process, and is often very noticeable especially when an engine is not at full running temperature. Even then it is evident under various conditions.
I'm not an out and out expert, but I would want to eliminate the easier possibilities before assuming HG failure.

[Kevin Wood]

It's normal for a cooling system to be under pressure. The expansion of the coolant as it warms up causes this.

If it starts to overcome the valve in the pressure cap on the expansion tank you need to start worrying but it's normal for the hoses to be hard.

Head gasket can pressurise cooling system but there would need to be more symptoms for a conclusive diagnosis. Are there any other symptoms that make you suspect the head gasket?

Kevin

[PaulW]

The coolant should also still be a good colour and clarity.  If the coolant water is turning black, then thats also a sign the HG is on its way.

If its mixing with oil and has got brown goop in it, then could most likely just be the oil cooler (check the dipstick see if the oil there is fine if you have goop)

[Albus Dumbledore]

I don't have any other symptoms that suggest HG, no oil in the water or anything, just this steam type of thing coming from the eks. tank. No bubbles when engine running and cap off, but gurgling. (maybe it's a desperate atempt to find just something that might be my problem)

I'm not sure if I got the coolant system unblocked. The heater is working again (didn't before), I degreased the whole day yesterday, took of the rad and rain hot water from the tap through, then degreaser, then hot water, then cold from the draining hole, top and bottom hose.

What to do next? Or should I degrease more?
The RMP isn't constant when car is standing still, but it's not jumping wildly:) If I push the gas pedal is a nice smooth sound (It became smooth after I sorted my EML).

[PaulW]

Try another coolant bottle cap, I've had a few of those fail on me before and hiss away under normal conditions.

There about £22 from vx or something like that, second hand isn't worth the bother as you can't guarantee those will be fine either!

Also, another thing to check, if you have hissing, as the rim around the top of the expansion tank cracked at all??  They have a habit of going there (replaced mine not long ago and its resolved a long-standing slow coolant leak!)

[Albus Dumbledore]

I don't think I have a crack in the eks. tank, but I'll check. I'll try getting a new filler cap.

By the way, when the hoses get rock hard, still the radiator is cold (hot water not coming to the rad).

Should I maybe disconnect all hoses to clean them?