Fox Help diagnosing a problem

[1988GTRagtop]

Hi was looking for some input if anyone has had same issue. Got an 88GT with 76k original on motor. Did a cylinder leak down test, and all cylinders came back with less than 15% loss. Except for cylinder #6. That one has over 50% loss. If I remove to oil filler cap I can hear the air hissing out. Does this sound like it could be a bad seal somewhere? Or am I looking at a bad ring?

 

[General karthief]

Or something holding the valve open.
does it smoke or have a miss?

 

[1988GTRagtop]

There is no misfire, it does smoke a white / gray color. It does idle a bit rough

 

[General karthief]

Do a compression test on that cylinder (remove all the plugs and hold the throttle wide open) note the psi then squirt some clean oil into the spark plug hole and check compression again, if the psi rises it's likely rings.
You could try squirting some trans fluid (small amount slowly) at like 1000-1500 rpms and run it till the smoke clears (it will smoke, alot) that can burn off the carbon deposits that could be holding the valve open. This is done when the compression does not change after adding oil to the cylinder for the second compression test.
What did that spark plug look like?

 

[1988GTRagtop]

The plugs were recently changed, less than 5k on them. But when I did pull it out, it had normal wear on it. Nothing out of ordinary.

 

[General karthief]

There is also the possibility of a head gasket problem.
one step (or stumble) at a time

 

[1988GTRagtop]

Thanks for the info. I’ll try it out and see what happens. Just trying to figure out if it’s the ring. Don’t know if it’s something I’d be able to do.

 

[jrichker]

Hi was looking for some input if anyone has had same issue. Got an 88GT with 76k original on motor. Did a cylinder leak down test, and all cylinders came back with less than 15% loss. Except for cylinder #6. That one has over 50% loss. If I remove to oil filler cap I can hear the air hissing out. Does this sound like it could be a bad seal somewhere? Or am I looking at a bad ring?

Putting compressed air into the engine cylinders is the best test for compression and leakage. If you hear the sound of compressed air leaking at the oil filler intake, you probably have a broken top ring or damaged piston. If you have a broken piston ring, it may have scored the cylinder wall.

 

[1988GTRagtop]

Putting compressed air into the engine cylinders is the best test for compression and leakage. If you hear the sound of compressed air leaking at the oil filler intake, you probably have a broken top ring or damaged piston. If you have a broken piston ring, it may have scored the cylinder wall.

That pretty much confirms my suspicion as well. Thank you

 

[7991LXnSHO]

Air out of the oil filler cap is a big red alert for what jrichker says. Please let us know what the damages or Halloween horror show ends up being.

 

[1988GTRagtop]

Air out of the oil filler cap is a big red alert for what jrichker says. Please let us know what the damages or Halloween horror show ends up being.

Kinda stuck at a crossroad on this one now. Car also has typical rust in strut towers on top of oil leak from pan. Did this test to see how far bad the motor is before I decided on how far to go with it. And this test just confirms my fears.