compression test?

[dibdub]

just reading post by blue mk2(sory to here bout problem) .what is a compression test?and how is it done?sorry if i sound bit stupid.thanks for the help anyone.

[Blue MK2]

trust me im not that clued up in the engine area myself

Its some sort of test that tells you if your head gasket is leaking.

If its possible to find a test kit at halfords then ill use it and return it... lol

[golfvr6]

A compression tester does what it says, it tests each cylinder for compression pressure. It simply screws in instead of the spark plug, you disable fuel and ignition, then crank the engine on the starter with the throttle wide open.
If pressures are low then you can pin point problems with piston bores/rings or valve guides/seats or headgasket problems.
I would shell out for one, they are not expensive and are worth having.

[Blue MK2]

roughly how much VR? Gonna grab one 2moro

[richandhazel]

Shouldn't have to spend more than ?20, probably about ?15

[richandhazel]

roughly how much VR? Gonna grab one 2moro

Now that you have that Bentley working, have a look at compression testing........gives you some good info in there

[Blue MK2]

ohh Rich your spoiling me today aint ya!

[Helios_Blue_Valver]

Compression test may not tell if the head gasket is going though. If you have low compression on a cylinder try a teaspoon full of oil down the spark plug hole. If compression improves then you have worn rings. If not bad valves. If you have a leak between an oil passage and the water jacket compression check won't show it. in that case you need an exhaust gas analysis.  If it is between the water jacket and a cylinder though a tell tale sign would be lots of pressure in the cooling system with the engine running. Same with an oil port and a cylinder. As everyone said though do a compression test though as that is the easiest path. if you don't turn up anything out of the ordinary than take it out for a good run and see if the mayo reappears under the oil cap. if it does get the exhaust gas analysis done. Loss of power is a big indicator to low compression though as is hard starting. Hope for the best mate. let us know how it goes.

[golfvr6]

If there is poor compression in two adjacent cylinders then the likely cause is a blown head gasket. Gasket failures between cylinder and water jacket will show as the hoses go rock hard quite quickly and the expansion tank vent will leak all the time as the pressure in the system is getting too high. Testing the coolant system for exhaust gases will quickly show this.

[Helios_Blue_Valver]

If there is poor compression in two adjacent cylinders then the likely cause is a blown head gasket. Gasket failures between cylinder and water jacket will show as the hoses go rock hard quite quickly and the expansion tank vent will leak all the time as the pressure in the system is getting too high. Testing the coolant system for exhaust gases will quickly show this.

Sorry didn't think of that. lol. was a bit on the sleepy side last night. i was more thinking of a leak between the water jack or oil passages and a cylinder. 100% right though you are.