Pressurised coolant tank

[metalworker0]

Well, what i said before ...a pressurised cooling system after overnight stand proves its the headgasket, it's a no brainer .

Why? after its been done before.

1. Not done properly ...maybe head needed skim/clean up and it wasn't done
2. Cheap head gasket bought, I've done that once, on a rover 420, bought from an ebayer called Shirley ..noticed that the layers (MLS) did not line up when i put it on- waveyness between layers ... slept on it... or rather didnt sleep ...and took it off the next day and bought a "PAYEN" one.
3. Cracked cylinder head - not noticed when changed.
4. Used the same head bolts again ..
5 Head is warped
6. Replaced by incompetent mechanic who did not have a torque wrench.
7. Was never done .. you were lied to !

Temperature fluctuations
can happen with sensor that is defective or faulty thermostat. or having air locks near the sensor. (air locks would be when the sensor is high up in old style system near the top hose and stat housing)

Human symptoms
Confusion , baffled , lost , guessing , wandering, thinking youve cured it , all common for the owner that has one on its way out , that isn't showing itself in full, head gaskets can be sneaky and deceiving.... you can waste months of time thinking about it, then one day, it goes big style.

The cure
You either guess and replace - or you buy all the tools necessary to do the full diagnostic tests ... cooling system pressure tester , sniff tester , compression tester , boroscope, leak down tester. laser temperature reader gizmo. and still end up replacing it .

all the best.mark

[T350camper]

I'm not going to repeat everything metalworker has said (although I agree with all of it) but head gaskets can be very sneaky and don't always fail in the obvious manner discussed in many a good pub over a few pints.

I had a car some years ago that would use a litre of coolant for no reason at random. No other symptoms, no leaks or temperature fluctuations, no steam from the exhaust etc. Then it would run for weeks or even months and not use a drop. Eventually I decided to remove the cylinder head and found the tinniest of tracking marks in the gasket. It was only at certain temperatures that the failure was occurring between a cylinder and water jacket. New gasket and head refaced...solved.

Also a thermostat that does not fully close will give you those temperature anomalies and the fan will not cut in if the temp next to the sensor is below the required level.

[andz327]

How you checking fan ? ? It won't come on until its up nearer the red and hard to get them up that high

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