Compression leaks on compression check

Recently timing belt of my son’s 2003 Mitsubishi Eclipse GT V6 slipped and we replaced it ourselves correctly with recommended way. After the the car started at the first attempt. As we hear some unusual noise, we stopped the motor and did a compression test. All 6 cylinders had compression over 150. But three cylinders couldn’t hold the compression and the gauge pressure went down slowly. Though I searched about the issue, I found it nowhere in the web. Would you please explain the situation we have faced and any solution. Thanks

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[Richard KirshyParticipant]

I think it would be wise to perform a leak down test on each cylinder
The results are pretty straight forward:
With both valves in the closed position (TDC) for each cylinder tested …
If it shows good on the gauge all is well
If it shows lower and its loosing air
There are basically 4 paths it will go.
If you hear air coming out the throttle body, you have a bent intake valve or damaged valve seat
If you hear air coming out the tail pipe, you have a bent exhaust valve or damaged valve seat
If you heat air coming out of the oil fill spigot on the valve cover, you have blow-by of the piston rings into the crank case.
If you see bubbles forming in the radiator with the cap off, you have a bad head gasket at best or a cracked head or engine block.
If you hear air escaping from between the head and block ( soapy water will help pin point the area) your looking at the same issue(s) as the one above.

• This reply was modified 2 years, 8 months ago by  Richard Kirshy.

[Nara KaruParticipant]

Thanks Richard. Ill try it. Best regards

[Author]

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