10 replies to this topic

[lewismason]

I recently did a compression test in an attempt to solve my idle problems. The results were:
Flywheel - 150 - 125 - 125 - 150 - radiator
I know they aren't horrendously low but they still differ more than 10%.
What's everyone else's opinion?

[Boycie]

Probably not enough to cause significant running issues on a standard road car.. but I'd say you either have the usual leaky valves/ worn rings or maybe a leak between cylinders 2 and 3.  Perhaps the head gasket is on its last legs.

[Carlos W]

Was the throttle wide open when you did them?

Drop a little oil in the bores and see if it improves, if it does it's rings

[minidave54]

I have a similar issue with my 95 spi, although my overall figures are higher.

It's used regularly, would people consider it ok to drive until i get time to take the head off for investigation.

[sonikk4]

I have a similar issue with my 95 spi, although my overall figures are higher.

It's used regularly, would people consider it ok to drive until i get time to take the head off for investigation.

 

If its running fine without using oil or water then carry on chugging along. Do a leak down check to confirm whether its rings or valves then you can budget for what you want to do later on.

[Cooperman]

I recently did a compression test in an attempt to solve my idle problems. The results were:
Flywheel - 150 - 125 - 125 - 150 - radiator
I know they aren't horrendously low but they still differ more than 10%.
What's everyone else's opinion?

That is not as it should be. Do a cylinder leakage test with the engine warm. If there is leakage on 2 & 3 best to remove the head and take a look inside. Check valve seats and re-lap/replace as necessary. Inspect the bores for wear and then proceed as necessary.

[minidave54]

Cheers for the reply sonikk, it's not using any oil or water so i will carry on for a while. Though I would like to get it sorted before IMM.

Not too sure how to carry out a leak down check though. Can you give me some advice.

[carbon]

Compression test results depend a lot on the engine spec, condition, and how test is carried out (battery condition). But 150psi is low, even for a low compression motor, and the difference of 25psi between cylinders suggests head gasket could be starting to fail between cylinders 2 and 3. This would not show up as change in oil or water use.

[lewismason]

Thanks everyone,

[lewismason]

What symptoms would I have if it was chuffing between 2 and 3? My lumpy idle is the problem at the moment, can't get the speed right and it runs very rough from cold.

[carbon]

If the head gasket blows between 2 and 3 it sounds like a tractor, runs rough, and you lose a lot of power.