basics on checking compression

T

tobers

Junior Member
It has been suggested that I test compression, cold and hot, to check for a possible valve problem. It's a 1997 4 cylinder. This is what I'm thinking:

1. pull all of the spark plugs
2. disconnect the EFI fuse
3. disconnect the spark plug wires from the coils
4. crank it 3-4 times to test each cylinder.

I was thinking I'd test the compression cold first, and put anti-seize on the plugs when I put them back in to be sure that when I pull them hot they don't damage the aluminum head. Will this protect the head?

Then do the same sequence when it is hot.

Is this right? Any other suggestions? What numbers should I expect cold? hot?

thank you!
 
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Hot should be between 145-175/180. Not sure what cold should be but not sure why you'd want to test that anyways. And ALWAYS use anti-seize on spark plugs. Hot/cold doesn't matter. Different materials will end up seizing together and then you are in for a world of hurt next time you go to pull them.
 
tobers said:
It has been suggested that I test compression, cold and hot, to check for a possible valve problem. It's a 1997 4 cylinder. This is what I'm thinking:

1. pull all of the spark plugs
2. disconnect the EFI fuse
3. disconnect the spark plug wires from the coils
4. crank it 3-4 times to test each cylinder.

I was thinking I'd test the compression cold first, and put anti-seize on the plugs when I put them back in to be sure that when I pull them hot they don't damage the aluminum head. Will this protect the head?

Then do the same sequence when it is hot.

Is this right? Any other suggestions? What numbers should I expect cold? hot?

thank you!
Click to expand...

You can usually diagnose a bad valve just looking at that cylinders spark plug and comparing to others to see if it has fouled. Bad piston ring will usually get oil on the plug.

Do compression test and make sure you keep the throttle pressed so the throttle plate is open during testing. Hot or cold should not matter. If you have a low cylinder than move to a leak down test which will show you where the issue is.
 
Forgo using the anti-seize.

As Jay said have the gas pedal to the floor before cranking. I didn't pull the EFI fuse and didn't have a problem.
 
Kill spark, kill fuel, pull one plug at a time and check compression on each cylinder 3-4 times to get a good average reading. Be sure your battery is fully charger or have it on a charger while testing and have the throttle wide.
As far as anti seize goes as an auto repair tech I rearly use it on spark plugs and if i do it is a very small amount. Spark plugs ground to the cylinder head and if they are all gummed up with anti seize it can effect the continuity with ground and cause weak spark and misfires. Just talking from experience.
 
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AZ4Running said:
Kill spark, kill fuel, pull one plug at a time and check compression on each cylinder 3-4 times to get a good average reading. Be sure your battery is fully charger or have it on a charger while testing and have the throttle wide.
As far as anti seize goes as an auto repair tech I rearly use it on spark plugs and if i do it is a very small amount. Spark plugs ground to the cylinder head and if they are all gummed up with anti seize it can effect the continuity with ground and cause weak spark and misfires. Just talking from experience.
Click to expand...

This is true, when running high boost on our turbocharged cars, we would fight misfire or spark blow out. I did everything known to man until I found the antiseize was the issue.
 
tobers said:
It has been suggested that I test compression, cold and hot, to check for a possible valve problem. It's a 1997 4 cylinder. This is what I'm thinking:

1. pull all of the spark plugs
2. disconnect the EFI fuse
3. disconnect the spark plug wires from the coils
4. crank it 3-4 times to test each cylinder.

I was thinking I'd test the compression cold first, and put anti-seize on the plugs when I put them back in to be sure that when I pull them hot they don't damage the aluminum head. Will this protect the head?

Then do the same sequence when it is hot.

Is this right? Any other suggestions? What numbers should I expect cold? hot?

thank you!
Click to expand...
my opinion is, that unless you are experience a problem, there is no reason to do it. if it runs well, just drive it.

if you are using this to diagnose an issue, then carry on with what you have planned.
I think a cold test will be plenty.

to add to your list, put a battery charger on. so you know its not getting drained and cranking slower, thus skewing the later test results.
 
I was always taught to use antiseize only on the threads closest to the insulator, leaving the threads closest to the electrode end dry. I've never had a problem with misfires from excess antiseize and no seized plugs.
 
I had two plugs nearly seized in my engine because they didn't have anti-seize on them. Took me over two hours to remove those two plugs. Guess we'll just agree to disagree but anti-seize will continue to be used on all of my spark plugs.
 
cashmoney said:
Surely you jest.
Click to expand...

Nope, he's right, according to NGK. See #1 in attached. I've forgone the anti-seize for the last ten years and never had a problem. I only use NGK, torque to spec, and change every 30k.

Toyota didn't use it at the factory, by the way.
 

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