Low compression 2 cylinders
 

Hey guys I have an 86.5 MKIII and did a compression check with the #4 & #5 were low. I think the #4 was 120psi and the #5 was only 90 psi. What could be the problem? Rings? HG? Any help would be great!
Thanks!

If your compression tester is like most it has an air chuck fitting on it, take the schrader out of the hose and the radiator cap off and hook an air line to it while its on the worst cyl. If the coolant starts to overflow or bubble then you have a bhg. Either way with those values I would think bhg, rings are not normally a problem on these car, or at least you will have lower values in all the cyls. Also bent valves don't normally happen so that should not be an issue either. If you want to check the rings, put a small amount of oil or trans fluid in the cyls and redo the compression test, if you get a large increase in compression it will be rings..

It's your piston rings. They don't always show low on all cylinders. 90psi. is definatly not caused from a bad heasgasket. But since it is free to test it. its worth a try. but I got 100 bucks on rings... rings wear out on any car regardless of make. Although they are not as prone to ring problems as they are bhg. They do wear out. In your situation is say rings.. especially unit has high mileage. Or has the boost cranked up above stock

Sorry I forgot to add that its a non turbo car.. has a little under 160,XXX. Ive been told from numberous people its either the rings or BHG. I was thinking about buying that "Blue Devil" sealant for the mean time, but I was trying to confirm it was a BHG. I dont really want to have to take apart the head because I want to do a 1jz swap in a month or two. But if it is the rings then Ill have to take the head off.

Also it has some white smoke when I start it up coming out of the exhaust, I normally only drive it around town once a day.

White smoke is a sign of piston rings. Blue smoke is sign of BHG. Like i said. bhg won't affect the compression by that much... jz swap is coming early..you will love it. I love my jz..

Where did you get your JZ? I was looking online.. the cheapest i can find one with motor and tranny is like $2100... like $1400 for just the motor. Know of anyplace cheaper? trying to buy from a direct source that has a warranty incase anything happens.

http://www.jrautoparts.com/clip_toyota_1jz.htm

3k shipped. No warranty but he sent me a video of it running. Trust me if u dont buy a front clip a 4 day project will turn into months trying to get all the little pieces

i was told white smoke was antifreeze, and blue smoke was oil...
doesnt make sense either that 160'000 would have bad rings...

ive had 4 supras and never experienced bad rings, my 85 2.8 was running 360'000km and still running strong

Yup, you've got it right

http://www.youtube.com/watch?feature...&v=7XTrPKt9Tnk

This was caused from a hole in a piston. White as can be...

Also when my turbo oil seals went out it was white also. The color of smoke is a rule of thumb not written in stone anywhere

160k is pretty good out of rings if it wasn't cared for properly... and again BHG won't lower the compression that much..IMHO

160'000 to have bad rings you would need to have putting the wrong oil in for 10 years or somthin??

does the 1j also have a ct26? because there antifreeze cooled. if the seals were gona bad enough could antifreeze be forced into the head??

that is some mean smoke comin from ur 1j

That's not my 1j. thats a buddy of mine. Melted a hole in a piston so its burnn oil with every stroke...

1jz use twin ct12a turbos. but they are antifreeze cooled..

my turbo that went out was on my old 7mgte. it was just the oil seal that burned out. The only way antifreeze would burn from the turbo is if it leaked into the oil passages and the oil seal was burned as well..


160k miles is 257,495 km. So it is definatly not un heard of to have rings go at that many miles if oil has not been changed regularly

oh ya i forget you Americans use miles,
we igloo people use kilometers so yea... my bad

Hey so Ive never changed piston rings before.. Was wondering if anyone could load some pics of the process. thanks for the help so far guys. appreciate it.

You don't have enough light in that and youtube sucks for color accuracy, but that looks plenty blue in a couple instances... and you apparently don't know precisely what you're looking for. Burning oil is not crayola blue, its bluish white to a bluish grey. Some oils may have a little less bluish cast than others but it's always there. And it's pretty hard to see unless it's sunny out. Looking at that video I wouldn't have been surprised to find that the HG had let go as well.

Coolant is water, glycol and sulfates. When burning coolant you're looking at mostly steam, go boil some water and report back please.

Oil burns blue normally, coolant is white, unburnt fuel is black. But when you have a lot of oil burning it will be white and it will be a lot of smoke. My turbo went out and it was blowing a lot of white smoke, but I burnt 1.5qt of oil in 30 miles.