MY compression test results!

[sunnys14]

i just compression tested my car. here are the results...

#1 - 45psi#2 - 60psi#3 - 60psi#4 - 60psi

the thing that is weird is when i pulled the #4 spark plug out, there was oil on it... as u can see, my motor is pretty much fuk'd. so heres the question, is this the outcome of a blown headgasket or blown ringlands?

i hate KAs...

[fabio420]

both (but with KA's more likely ring lands)

[virus77]

Ive never seen someone blow all cylinders so evenly. Is your gauge accurate.

[sunnys14]

yes it is. i check it 3 times and thats what i came up with. brand new tester also.

[S14tat]

you sure it was done at WOT? and did you pure down a teaspoon of oil down each spark plug hole to see if the compression went back up or not?

[sunnys14]

it was done at WOT. i did not pour any oil down the cylinders to check. i will now that u reminded me! brb with the new numbers.

[sunnys14]

OK! here are my new compression test results after pouring oil in each of the cylinders:

#1 - 60psi#2 - 70psi#3 - 90psi#4 - 80psi

weird stuff... so whats the verdict? i do not know, thats why im asking you guys.

[Craving4Boost]

gotta be headgasket now...if ringlands were blown the compression wouldnt go up.

and how come you have to do compressioon test at WOT? i dont..

[4felix20]

when i blew my motor, i pulled the exhaust manifold off and noticed #3 port was oily unlike all the others. when i finally got the head off, #3 piston had a fat chip out of the perimeter. don't know if that's gonna help since you already poured some oil down each cylinder...

crave4boost, compression needs to be tested at WOT for accuracy. otherwise the throttle butterflies can interfere.

[sunnys14]

my previous motor had the same thing u were talking about. where the head meets the manifold, it was oily also. #3 detonated. as for this motor, does anything think a head gasket will fix this problem???

[KATwo40]

Only one way to find out. Yank that head off and start checkin' stuff.

[Skidmark]

That's really odd. The last motor I blew up was cylinder 3 also, had a nice little chunk missing from the edge of the dish. Interesting... BTW if your compression goes up with the oil in the cylinder then that means your rings are NOT holding full compression, the oil is creating a temporary seal around the piston & ring allowing it to hold a little more compression. However, your numbers are still way too low so that's more than likely not your only problem. With equally low numbers all the way across my guess is either a severely blown head gasket or you may have warped your head and/or stretched your head bolts unless there is some error in your testing that we don't know about. If you have access to a leakdown tester that might be a good next step. Knowing exactly how fast your cylinders are losing compression will help determine what's wrong. You may even be able to hear where the gas is escaping from. Also I'm not sure if you've done any valvetrain work on your car recently but if you have you might want to doublecheck all that to make sure your valve timing is correct. That's really all I can think of at the moment aside from actually pulling the head, but then again that's more than likely something you will have to do anyways to fix whatever is wrong with the engine. Anyhow good luck, keep us posted.

[nissanfanatic]

Maybe your timing chain just skipped a tooth or something....???

[KATwo40]

Maybe your timing chain just skipped a tooth or something....???

That occurance is so incredibly rare and nearly impossible. It's more likely on a belt engine, but not chain.

[fiznat]

if ringlands were blown the compression wouldnt go up.

Sure it would! Compression goes up with a capful of oil on engines with bad rings or ringlands. ...Not if theyre totally destroyed, but if theyre not sealing well, oil helps to make that seal and bump up the compression for a few strokes.

It doesnt really matter at this point if the problem is headgasket or rings. As far as I see it, at the very least you're going to be pulling the head off either way-- so you might as well get to it and see what you find.

[fabio420]

It doesnt really matter at this point if the problem is headgasket or rings. As far as I see it, at the very least you're going to be pulling the head off either way-- so you might as well get to it and see what you find.

EXACTLY!

[virus77]

I know this is a stupid question but did you crank it 4-5 times over or just once. You never know, I've seen people do worse so I thought I would ask.

[sunnys14]

crank it over as in letting the starter turn for like 10 seconds? yes i did that with every cylinder, and i also checked 3 times and those are the results i came up with...

[virus77]

dont be down man, just be sure to build the motor correctly and you're gonna have a whole new beast.

[nissanfanatic]

That occurance is so incredibly rare and nearly impossible. It's more likely on a belt engine, but not chain.

Its not all that rare....http://www.240sx.org/faq/articles/timing.htm

Read article "Can I replace my own timing chain (or, better yet, why would I want to)?"

If tensioners wear out, or something isnt' set up right, or chain is stretched, skipping a tooth is completely feezable.

[TravBear2]

But if you dont go cheap, you wont have the problem iwth a bad tensioner or bad chain... And on that note, those chains last for like 200,000 so....

[Craving4Boost]

holy smokes i got the oil-compression thing backwards

[sunnys14]

my cheap fix: i am going to pull the rod and piston from my spare block thats been sittin around and swap them into the existing one. does anything think that this is a bad idea? your feedback would be great.

[SonyPete]

sunnys14 still hasn't verified if he did the testing at WOT. Feels like he takes one half of what you guys are saying but not the second half.

[fiznat]

sunnys14 still hasn't verified if he did the testing at WOT. Feels like he takes one half of what you guys are saying but the second half.

Yes he has:

it was done at WOT.

I think that pretty much clears up that issue lol

Sunnys, replacing the internals with your other internals should work decently well, although you should use new rings and re-hone the cyls (there is a hand-powered tool you can get to do it) so that the rings wear in to your cyls properly. You cant just throw any old already-worn-in rings in there. Also be aware that by putting the same OEM stuff in there, you're setting yourself up to have this whole nightmare happen all over again...

[sunnys14]

i was reading on ORION's site that he did almost the same thing that i am about to attempt. so if he did it, and it works, so why not try it?

[nissanfanatic]

Make sure they are the same grade piston.

On the top of the piston, you will see a number on top and a number on bottom. The number on bottom shoudl be "05"

The number above that is the grade of pistons. It will be "1", "2", or "3". Make sure that this number matches the number on your broken piston. IE, if the broken piston is a "2", make sure the used good piston you plan on putting in is a "2". Most KAs use grade 2s... My junkyard engine had all grade 2 pistons.

And use the rings off the busted piston. Swap them over to the good piston and you should be good to go. But... if your rings are broken or become broken, I'd just put the previous rings on and go for broke. Worst that will happen is compression will be low, but ****, thats better than compression being at 0 and not having a car...

BTW, this is my backup plan too. Only bad part... I'm more likely to spin a bearing than anything...

[virus77]

you can do it. Thats what i did to my crx back in the days when it dropped a valve on one of the pistons. Needless to say its smoked a little but she ran.

[sunnys14]

what about honing the cylinder walls, and dropping the complete piston over? that wouldnt work? i heard rings get out of shape once u take them apart.

[AZhitman]

What's up with checking it at WOT? Are you suggesting checking it while the car is running?

I check mine with the coil and injector plugs disconnected and crank 10 revs.