Celica Forums General Discussion General compression bad? how much to fix

I did a compression check on my buddy's 97 supra and it looks pretty bad. The difference were between 25-40psi. Lowest was 146 and highest was 180. To check if there was a leak, i added some oil and run the compression test again and discovered that it was a leak. This is not good considering that a stronger cylinder will work harder, stressing the other cylinders to keep up. This will build problems in the future.

How much do you guy's think it'll cost to replace the rings? I need more information on this and couldn't find enough that i need through search. Is there something that he can do to treat this? Before he starts boosting, i told him that its good in the long run to fix it.

are you sure that the compression is being lost in the rings and not in the cylender walls?

IDK how much piston rings are, but to replace them you have to take out the piston itself so you might as well replace the stock piston with an aftermarket forged one, especially if he's going FI.

You actually need to do a leakdown test, He may get lucky and only have some bad valves. Just doing a compression check will only tell you there is a problem with that "hole" a leakdown will help you pinpoint just where the problem lies.

Yeah, as said do a leakdown test to pinpoint what the problem is instead of just guessing what it MIGHT be.

Goto Suprastore.com.. click on the I-Forums link in the menu on the left... ask the question there.. they will be able to help you there more than anyone here will.

Where are all the places compression can leak?

I don't know anything about this

any place to read up on this topic?

An engine is an engine whether it be supra, celica,chevy,ford,etc. Even a brand new motor can have up to 20% leakdown. Heres a brief summary on what a leakdown test is...

With the sparkplug, valve cover and exhaust manifold removed and the piston at top dead center 100psi is inserted in the cylinder via the sparkplug hole with a special tool consisting of a one way valve W/relief and a pressure gauge, 20% leakdown is in a nut shell 20psi.

How this test can pinpoint where a problem lies is like this...

While inserting the 100psi if you hear or feel...

1. air rushing in the oil pan its worn or broken rings

2. air rushing from the exhaust port its bad exhaust valves

3. air rushing in the Intake manifold its bad Intake valves.


Hope this makes a little sense to everybody

basically, its not too hard to determine the bad part that compression is leaking, you arent gonna have a problem with compression leaking from your Intake valves if your piston rings are shot...

just gotta think about it for a few secs.

Try this...
a. Insert a compression gauge into the spark plug hole.
b. Fully open the throttle.
c. While cranking the engine, measure the compression pressure. HINT: Always use a fully charged battery to obtain engine speed of 250 rpm or more.
d. Repeat steps a. through c. for each cylinder. NOTICE: This measurement must be done in as short time as possible.
Compression pressure: IZZ-FE: 1,500 kPa (15.3 kgf/cm2,145 psi) 2ZZ-GE: 1,000 kPa (10.2 kgf/cm2, 145 psi)
minimum pressure: 1ZZ-FE 1,000 kPa (10.2 kgf/cm2, 145 psi) 2ZZ-GE: 1,000 kPa (10.2 kgf/cm2, 145 psi)
Difference between each cylinder: 1ZZ-FE: 100 kPa (1.0 kgf/cm2, 15 psi) or less 2ZZ-GE: 110 kPa (1.1 kgf/cm2, 16 psi) or less
e. If the cylinder compression in one more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat steps a. through c. for cylinders with low compression.

If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.

Sorry thought it was for a Celica. This might help some one here though. I'm going to leave it if no one has any objections.