Leakdown test on used engine

[indyzhp]

I'm looking at a used engine that's obviously been sitting a while. I'd like to perform a leakdown test on the engine to determine valve health. I've got some questions about how valid the test will be?

to be clear, 1998 M62B44 (non-vanos)

1. Most instructions say to do on a warm engine. Being out of the car and not running, this is not possible.
2. I'm assuming the lifters will most likely be empty, so they will not be fully bled.

Will either of these two situations affect the validity of a leakdown test? Or anything else on an engine that's been sitting?

[bluptgm3]

I would pull the plugs and add a small amount of light oil to each cylinder and hand crank the engine a dozen times (+/-) and then test.
The valves for a given cylinder needs to be closed during the ‘leak down test’, so empty lifter won’t matter.
Plan on spending a couple hours accomplishing this test.


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[edjack]

Once you have the plugs out, why not spin it over on the starter for 10 secs or so?

The trouble with performing this test on a cold engine is what will you use as a pass/fail?

[JimLev]

Trying to pour oil into the spark plug holes and then getting good coverage on the cylinder walls isn’t the easiest thing to do.
Have the piston at the bottom of the bore then spray some fogging oil in thru the plug hole.
https://www.amazon.com/STA-BIL-22001...NsaWNrPXRydWU=

[djb2]

Just run the leak-down test. Don't worry about warming up the engine or doing anything special.

If you get questionable results or lots of leaking through the crankcase, try again with oil. Fogging oil is a good choice with the cylinder slant, although that might not be an issue with the engine out of the car.

[MotorMouth93]

A leakdown test at room temperature will still give you a decent idea of engine health, as long as the numbers are fairly consistent I wouldn't be worried about it. On a cold engine I'd be happy with <15% across the board.

[vinyldude]

While not ideal, a leakdown test on a cold engine will still tell you if the valves have any major leakage or not. A good result will be that with each cylinder you'll hear the leakage happening via the crankcase and nothing via exhaust or intake valves.

[indyzhp]

Summary here:
leakdown test on cold engine
1-82%
2-92%
3-48%
4-78%
5-96%
6-89%
7-34%
8-94%

I called the place I bought it from and they are working to make it good. They ordered a new engine with less miles and should be compression checked and will hopefully get it to me by the end of the week.

However, my buddy and I were still wanting to look for the root cause, so we were working on the crankshaft bolt. Broke 2 1/2" breaker bars!! I still plan to do guides on the next motor for good measure.

Any advice for crankshaft bolt out of the car? I've got the crankshaft holder tool and plan to move on to supporting that on the oil pan, heat and aerokroil, then either 3/4" impact or my replacement 1/2" breaker bar with extension.

[philly98540]

What brand of breaker bars did you break? Name brands? A good quality 1/2" bar should hold up. A 3/4" will definitely hold.

[JimLev]

I’m using a 3/4” craftsman breaker bar with my 4’ floor jack handle on it.

[MotorMouth93]

Somethign I've come across when leak testing used motors is sometimes carbon flakes will get stuck in the valve seats and cause garbage numbers. Tapping the valve from the top can pop the valve open enough for air pressure to blast the carbon out so it might be worth a shot. I had a Honda B18 engine go from garbage test results to sealing up nicely just from gunk in the valves getting blasted out. 34% is pretty bad though so who knows.

[indyzhp]

Somethign I've come across when leak testing used motors is sometimes carbon flakes will get stuck in the valve seats and cause garbage numbers. Tapping the valve from the top can pop the valve open enough for air pressure to blast the carbon out so it might be worth a shot. I had a Honda B18 engine go from garbage test results to sealing up nicely just from gunk in the valves getting blasted out. 34% is pretty bad though so who knows.

That was our thought and why we kept going, but ultimately decided the 34% was low enough to be concerned about other issues. We were getting ready to pull the heads and hand clean the valves and do an upside down liquid leak test so that we could isolate valve issues versus cylinder bore/rings or ??

- - - Updated - - -

What brand of breaker bars did you break? Name brands? A good quality 1/2" bar should hold up. A 3/4" will definitely hold.

#1 was a Craftsman (although pretty old)
#2 was a Harbor Freight (so not really a surprise)
both broke right at the root of the square drive.

[philly98540]

Somethign I've come across when leak testing used motors is sometimes carbon flakes will get stuck in the valve seats and cause garbage numbers. Tapping the valve from the top can pop the valve open enough for air pressure to blast the carbon out so it might be worth a shot. I had a Honda B18 engine go from garbage test results to sealing up nicely just from gunk in the valves getting blasted out. 34% is pretty bad though so who knows.

Totally agree on this. My engine had some valves leaking a bit when I did my recent tear down and re-assembly. After re-assy, I put each piston at TDC compression stroke and put about 40 psi compressed air into each spark plug hole to check that everything was sealing good. I was getting some valve leakage that concerned me. I could hear it leaking out the exhaust ports and intake on a couple cylinders. I was thinking I needed to do a valve job. I slept on it and then thought it might be tiny carbon crumbs stuck on the valve seats. I put the air pressure back on the suspect cylinders and used a brass drift and hammer to unseat each valve by tapping down on the tappets. The compressed air "popped" out on each of the valves and removed the tiny crumbs. I got full compression back and no leakage. I continued with the re-assy at that point. The engine is running great.

Maybe your "bad" engine has this same issue?