502 MPI Leakdown test results

[dbkski]

1999 Mercruiser 502 MPI cold engine 70 hrs

Test results: #cylinder %loss
#1 15% #8 15% #4 15% #3 25%
#6 25% #5 25% #7 15% #2 25%

I do not know about leakdown tests but these numbers seem
bad to me. Please advise.

[Young Performance]

Those numbers aren't great but they are not horrible.Was the engine cold or hot. You also need to figure out where the air is leaking; is it going past the exhaust valves, the intake valves or the rings. If the motor has not been run in a while, then a little rust can form on the valve seats and stop the valves from seating completely. Need a little more info. Eddie

[dbkski]

This is an engine I am thinking of buying, not that I own. If
this helps narrow down my options or your opinions.

Engine was cold. Engine was run, at idle, 2 weeks ago.
Will try to get info on where the leaks were coming from.

[SB]

For a 502 and being cold that really isn't bad. They have a low tension ring package and not the tightest of pistons. Note: They are designed this way for good power and dependability.

Personally, I don't like cold leak down tests especially if motor has been sitting around for a while. A bit of crud or rust on vlave face / seats can dramatically influence (for the worse) these #'s where if engine is run these would disappear and engine is actually perfect.

Anyway - if a fresh water (or mostly) engine and no sludge and good maintenance, runs well, and good compression test, oh, and reasonable hours, then I'd have good faith in it.

Pretty hard to beat a Gen VI 502 hyd roller black Merc motor.

[Strip Poker 388]

Originally Posted by dbkski

1999 Mercruiser 502 MPI cold engine 70 hrs

Test results: #cylinder %loss
#1 15% #8 15% #4 15% #3 25%
#6 25% #5 25% #7 15% #2 25%

I do not know about leakdown tests but these numbers seem
bad to me. Please advise.

was that based off 100psi?

[dbkski]

Forgot to ask about what psi was used but all the "proper"
tools were not available for a perfect test. Most air loss was
at the exhaust. TDC was kind of "eyed up". Rockers were
tapped with a mallet when real bad numbers were showing
up - 50-60%. The numbers then went down to 15% then
back up to 25% on those few cylinders. Don't really know
what to think now. Probably not as bad as I thought? Opinions?

[Elite Marine]

You cannot properly perform a leak down test on an engine that hasn't been run recently.

If you are getting leak down though the exhaust valves it is more than likely carbon build up or light rust.

How did the valve train and valve covers look? Clean? Foam?

Looking into the engine could tell you alot about it.

[LS1 MOLESTER]

you're supposed to put a little oil in the cylinder to seal the piston rings and if pressure is still low then you know it's a valve.