Is there any point to a leak down test?

[Spetz]

Hi guys,

I did a cold compression test as at the time the car did not run and the results weren't good.

Since then I have started it and did a hot compression test, all cylinders read between 220 and 225psi so I was really happy with the result.

Does this mean everything is ok or can a leak down test still show a problem?

I have not driven the car much, but it seems to run fine.

Edit:
Engine is a 6A12 Mitsubishi MIVEC. It has had a full top to bottom rebuilt in 2009 but has since been stored and only now started up.

 

[Kira]

Smooth running with your even compression would leave me in "Happy Motoring" mode.
Turn each cylinder to where all valves are closed, add pressurized air and listen for leaking at the exhaust tip and at the throttle if you want to.

 

[Spetz]

Does it matter if I do it cold?

 

[doublebase]

I've never even really done a "hot" compression test. I'm always afraid to pull plugs out when the engine is hot - I always wait for it to cool - then run the compression test.

You could do. A wet compression test to check and see if you have a ring problem, just drop a couple squirts of oil down into the cylinder and run the test. If the results are higher than the regular test, then you have a ring problem.

A leak down test is good to actually isolate what the problem is. If the air is coming out the exhaust? It's the exhaust valve. If it's coming out the intake? Intake valve. If it's coming out of the oil dipstick tube? It's the rings or you have a hole in the piston. It's a pretty good diagnostic tool so you know exactly what you're dealing with. Oh and if there's air bubbles in your radiator? Head gasket, cracked head or cracked block.

 

[ARCOgraphite]

I h learned to Leave well enough alone - you keep messing, you will screw up something. Hi-Tension Ignition components don't tolerate being manhandled. They start leaking.

Enjoy the ride

I recently read in RodentRack
No more racy, turbo Mitsu's Stateside

 

[Trav]

A cold compression test will not give very informative results on any engine, some engines like air cooled and boosted engines can be very loose when cold and much lower numbers can be considered normal.
Doing a wet test on a cold engine will always show a rise in compression because it seals the cold contracted parts, the engine as close as possible to normal operating temp will give you correct results.

The easiest way to do this with aluminum head(s) is to crack the plugs loose on the cold engine and just snug them, let the engine warm up, shut it down and pull all the plugs.
Disable the fuel pump and ecm by removing the fuses, have an assistant fully open the throttle and crank it 3-4 seconds then check each cylinder.
Keep the cranking time as close as possible for each cylinder, your results will be pretty accurate.

A leak down test can be very beneficial in finding the source of lower compression by finding if its leaking across cylinders, into the crankcase or through the valves. It is also more accurate than a compression test.