Fox Help diagnosing a problem

1

1988GTRagtop

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Oct 31, 2021

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Oct 31, 2021

#1

• Oct 31, 2021

• #1

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

wonder how much it would cost to ship you a pair

Mod Dude

Aug 25, 2016

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#2

• Oct 31, 2021

• #2

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

 

1

1988GTRagtop

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Oct 31, 2021

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Oct 31, 2021

#3

• Oct 31, 2021

• #3

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

 

General karthief

wonder how much it would cost to ship you a pair

Mod Dude

Aug 25, 2016

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#4

• Oct 31, 2021

• #4

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?

 

1

1988GTRagtop

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Oct 31, 2021

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Oct 31, 2021

#5

• Oct 31, 2021

• #5

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

wonder how much it would cost to ship you a pair

Mod Dude

Aug 25, 2016

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polk county florida

Oct 31, 2021

#6

• Oct 31, 2021

• #6

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

 

1

1988GTRagtop

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Oct 31, 2021

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Oct 31, 2021

#7

• Oct 31, 2021

• #7

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.

 

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jrichker

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Mar 10, 2000

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Nov 6, 2021

#8

• Nov 6, 2021

• #8

1988GTRagtop said:

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?

Click to expand...

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.

 

Reactions: General karthief

1

1988GTRagtop

Member

Oct 31, 2021

6

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MA

Nov 6, 2021

#9

• Nov 6, 2021

• #9

jrichker said:

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.

Click to expand...

That pretty much confirms my suspicion as well. Thank you

 

7991LXnSHO

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Nov 13, 2021

#10

• Nov 13, 2021

• #10

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.

 

1

1988GTRagtop

Member

Oct 31, 2021

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Nov 13, 2021

#11

• Nov 13, 2021

• #11

7991LXnSHO said:

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.

Click to expand...

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.