How Do I do a COMPRESSION CHECK...1st time....details

[hopefulfan_dc]

I wanna know, in general, how to do a compression check...help

[Guest TurboSedan]

you want to do it with the engine at operating temperature. first pull ALL the spark plugs out. then disconnect the CPS from the ICM so the injectors don't fire while you're doing the test. screw the compression tester into the spark plug hole and monitor the gauge while a friend cranks the engine over. monitor how fast pressure builds up (should peak after 4-5 engine rotations). take notes of each cylinder and compare them to each other. each cylinder should be within 10% of each other.

[89GPSE]

correct. done

[Jcrow]

When I did mine, all the cylinders had 150 psi +/- 3psi

Just to give you an idea of what to look for

[joey b]

am I getting this right? At operating temperature you are supposed to pull the spark plugs? :?

[mihela816]

Yeah that seems like you're asking to strip the holes. I know why the engine needs to be at op temp, clearances and thermal expansion... but is there any safer way to do it?

[Guest TurboSedan]

to check compression...yes. check compression at operating temperature....that means pulling the plugs with the engine warm. there really isn't any way around it. i've done it many times even just to check plugs and i've never had a spark plug blow out or strip a hole (????). i know there is an underhood sticker that says you shouldn't, but i've never had any issues.

[JoroCorona]

If you go slowly on the plugs you should have no problem with the plug stripping the head. I pull plugs out of hot hondas without stripping them, and they are notorious for stripping. Just gotta be careful.

[Jcrow]

I did mine cold

[cutlsp]

I did mine cold

i don't think its very good for the aluminum heads to do a check with the motor hot. i'm going to be doing mine cold also this week.

[Guest TurboSedan]

will your rings be sealing 100% when cold? or the valve seals for that matter.

[19Cutlass94]

pulling the spark plugs out when the engin is warm is a bit sketchy but its the only way to do it, well to do it the right way anyways

[joey b]

I would probably loosen the spark plugs while cold, retighten, get to temp, then remove.

[Jcrow]

My friend has a 3100 and changed his sparkplugs the other weekend while the engine was hot, now the front middle plug is real sketchy, we were afraid to tighten it all the way because it seemed like it just kept spinning. It runs and the plug stays in but I wouldnt want to have to rip the heads off for a stripped spark plug

[hopefulfan_dc]

Thanx...I will safely do my test...while the engine is WARM....and like any fastener in AL, slow and easy....

 

very helpful

[Canada]

Do it while the engine is warm......not HOT. There is a difference there....

[Redwingvksm]

Meh.

 

I say cold.

 

All the cylinders should still read around 10% of each other...

 

These are aluminum heads - I (as a mechanic) - would NOT take the chance on my own car - as well as someone else's.

 

It shouldn't matter that much if it's cold - what a 20 PSI drop tops? As long as they are all relative to eachother you should be ok... :shock: