compression test?

[97gsxturbo97]

I was told to do a compression test with the engine hot. Then on the other hand I was told it is a bad idea to change the plugs when the engines hot because you risk the chance of stripping spark plug threads? So which is it then hot or cold when doing a compression test.

 

[91tizzy]

The reason you are supposed to do a compression test with the engine hot is because everything that is going to expand when the motor heats up has expanded(rings,cylinder walls, etc) and it gives you the compression the motor actually see's during use. If your careful with the threads hot or cold you should be fine

 

[4g63Powered]

+1 on the hot engine. You'll get incorrect readings on a cold motor, and that doesn't really help, now does it?

 

[1gDSM4g63]

Then on the other hand I was told it is a bad idea to change the plugs when the engines hot because you risk the chance of stripping spark plug threads?

Put anti-seize lube on the threads on the spark plugs next time. That will prevent seize and corrosion.

 

[97gsxturbo97]

ok thanks guys. I have always done compression tests on a hot engine. I was reading that you can not change plugs on a hot engine with aluminum heads becuase you will ruin the threads. Then I was saying well doing a compression test hot is contadicting that since you have to remove the plugs after the engine is hot.