Compression and leak down test question?

[Dave Kost]

Can you do a compression and leak down on a non running engine that is out of the car? If so, are the numbers accurate?

Thanks

[E Sully]

I do a leakdown on freshly rebuilt engines before installing, and again after break in. OCD. I know the numbers will be low slightly low before breaking the engine in, but it gives a quick indication if a ring or valve is not right. Much easier than installing and then having to drop the engine if the numbers are bad. It's also easier to actually hear where the air is leaking out from.

[Dave Kost]

Ed thanks for the reply.

My situation is that I may buy a engine without much documented history and want to do a leak down. Knowing that there could be other issues would the leak down/ compression results be accurate if done by cranking the engine by hand with all the plugs out?

Any other recommendations before purchasing the engine?

[BK911]

Crank the engine by hand to do a compression test? Please video and post results.

A cold leakdown should tell you enough. If all numbers are close and not too high, should be a decent engine.

[dad911]

Originally Posted by Dave Kost

Ed thanks for the reply.

My situation is that I may buy a engine without much documented history and want to do a leak down. Knowing that there could be other issues would the leak down/ compression results be accurate if done by cranking the engine by hand with all the plugs out?

Any other recommendations before purchasing the engine?

You can do a leakdown, but not compression if the engine is out of the car. You would need to crank with a starter for compression test.

What year/size engine?

You can pull valve covers and check head studs.

[Dave Kost]

2.7 rebuilt 40k ago
head studs replaced
higher compression pistons
chain tensioners
Pop off
engine looks clean
no docs but I can contact previous previous owner

[Porshaah]

A battery, jumper cables to the starter and a battery operated compressor or portable air tank (i.e. if an AC powered compressor is not available) will allow you to do all the tests you desire.

[Dave Kost]

I wore my arm out cranking ..... But I got 165 psi across the board!

[Guardsred911]

seems like a good outcome.....