Cylinder Compression Test

[PaulP38a]

While I've got the plugs out today, figured I might do a check on the compression, since I've got a test set here and have never used it...

1999 4.0 low compression engine with 178k. Head gaskets and heads were replaced 2 years ago.

It was a dry test, and I didn't warm the engine up first (oops).
Plugs removed, fuel pump fuse and relay removed. Battery charge ok.

Results in PSI:
1 = 130
2 = 130
3 = 125
4 = 130
5 = 145
6 = 130
7 = 130
8 = 140

Should I be concerned?

Would you expect the results to improve (or worsen :o) when done again "wet" and/or at running temperate?

cheers
Paul.

[wayneg]

Why are you looking for problems? stick the old plugs back, change the engine oil and carry on as before. Well that`s what I would do. If it ain`t Broke.................

[Blknight.aus]

all are just within 10% so your ok...

Id do a leak down on #3 just to find out where the compressions going.

[PaulP38a]

Thanks guys, will see if I can pick up a leak down tester from an auto shop tomorrow. I might even have enough air fittings in the garage to bodgy something up tonight.

Fuel consumption has been up a bit in the past few weeks and am looking at simple things... might just be some bad fuel, the MAF and/or air filter is filthy.

To do a wet compression test, how much oil should I squirt in the cylinder?

Use a syringe or a bit of clear tube I guess?

Cheers
Paul.

[33chinacars]

Compression figures look O'k. For a wet test 2 or 3 squirts from an oil can is all that is needed.

Not to much to worry about tho. As others have said "If it aint broke don't fix it "

Gary

[Blknight.aus]

less than 10ml but every pot must recieve the same amount...

usually once Ive put it in I turn the engine over by hand 2 full turns before going the starter, this ensures that your not going to "hydraulic" the piston and blow the gauge apart.

[RR P38]

I wouldnt bother with a wet test,
Why?;
How do you ensure the oil is all the way around the bore?
Is it a real world test?;
Not really, is it normal to have that much oil on top of a piston?

A warm test is the best way i would say.
Any compression test will give a different reading according to how fast you are spinning the engine.
All compression ratios are is a measurement of volume within the cylinder at maximum (volume) compared to minimum (volume).
You dont seem to have a great deal of variance across the 8 cylinders, up to 10% is the accepted range and beyond this you would probably start to look at valves/rings as a possible problem.

[rovercare]

I wouldnt bother with a wet test,
Why?;
How do you ensure the oil is all the way around the bore?
Is it a real world test?;
Not really, is it normal to have that much oil on top of a piston?

A warm test is the best way i would say.
Any compression test will give a different reading according to how fast you are spinning the engine.
All compression ratios are is a measurement of volume within the cylinder at maximum (volume) compared to minimum (volume).
You dont seem to have a great deal of variance across the 8 cylinders, up to 10% is the accepted range and beyond this you would probably start to look at valves/rings as a possible problem.

I agree, wet tests are a waste, if the compression is down to be of concern, your taking the heads of anyway

Warm it up, pull plugs, crank it with wide open throttle