Informative compression test info from my own car.

Should be in tech but I want everyone to see this…

I’ve done a lot of compression tests in my day, so user error is out of the question. However, I’ve always considered an engine who’s coolant temp is up to normal is ready to test.

With that said, I’ve always tested my Evo with the coolant temp up to normal, with no regards to oil temp. I’ve always had a cylinder that’s about 10psi lower than the rest, which at the time was little concern, but something to watch. With nothing else to do today, I took the car on a short drive to get the coolant up to temp and checked the compression. Keep note that the oil temp was 125F at the time of test. That aforementioned cylinder was ~15psi lower than the rest, my personal absolute limit to being ‘in spec’. Remembering that one time in the past, I had that same cylinder test the same as the others, I took the car on a longer drive and got the oil temp up to it’s normal range (about 180).

Checked compression. 180 across the board! The oil (and the rest of the engine) being that much hotter made the difference.

Conclusions-drive the car for at least 15 minutes before you pull a compression test. Yes, I’ve had cars test fine with a shorter drive, or even cold, but to eliminate all variables have the coolant/oil up to ‘full’ temp.

Que

Tengo un pene enorme. Si usted fuera a prueba de compresión mi pene, se leería más de nueve mil.

Yeah. What she said.

yeah thats the way to do it, BUT there is something obviously different with that cylinder. thanks god for thermal expansion…and broners when looking at evos

Possibly but I don’t care. It tests fine when the fluids are at operating temps.

Eso es lo que ha dicho!

cold eng temps is what indicates problems man . warm test are not a acurrate way of doing kid . im sorry i gotta be the devils advocate here . if a cyl is low on comp when cold and adding oil helps , that means a ring problem homey

I totally disagree.

Do a leak-down test y0.

Probably will just for fun. With the engine/fluids at full temp:number1

not saying a warm test is tottaly inacurrate but cold indicates more problems

Again, I disagree. But we’re def still cool for exchanging blow/handjobs yo

Why do you disagree Travis. Please do explain as I believe John stands correct here. SRS. every time I have done and seen it done was not at all normal operating temps. If it’s to help you sleep at night then so be it. Again not trying to be a dick just interested.

you both are right, but trav obviously doesnt care, and thats fine. lets just hope those rings aren’t on borrowed time

I would think the same as John. The rings shouldn’t require the heat (thermal expansion) to properly seal. If they do, then that tells me that they are still ok, but that they are on the way out.

if those rings had a goose…it’d be cooked

No.

Honestly, within 10% COLD isn’t really a big deal. If it was still low when warm I would worry… cold tests exaggerate problems.

soo were going to race before you get to operating temps?

thats all im getting out of this thread.