Engine Sitting Unused Loss of Compression?
 

If an engine is sitting for a few years would you be worried about a loss of compression?

I'm interested in a motor that was rebuilt but never operated, it has sat for several years.

If I do a compression test on it out of the car manually with a wrench, what is the procedure and what should I look for?

Thank you

Definitely a chance of it having poor compression.

Squirt some 2cycle in the ports as you turn it over you obviously won't get accurate numbers like this with a compression tester but strong even pulses are about the best you can hope for turning it over by wrench

Thanks would the compression come back all the way once I drove it around for a while?

Compression is built by the seals in the engine. Compression is lost by seals being worn or broken.

Since the engine isn't running, you aren't losing mechanical compression. But, you will want an oil film in there to help seal it up for starting compression.

A bone dry engine will need a little oil to help get it started. I would also highly recommend cranking the engine until oil pressure is built up, then trying to start it. This will lubricate the bearings and turbo with fresh oil. Just pull the ECU fuse, crank until you have good, solid, pressure, then start.

Dale

Thanks what I'm after is are there any permanent adverse affects to compression from letting an engine sit for years unused? Like Springs losing tension and seals becoming stuck and not be able to be unstuck by driving.

Depending on the results of the compression test, you can tell and sometimes differentiate if you have a stuck apex seal or a side seal failure. These can definitely be effects of sitting for too long, but go for the compression test first to see if you even have to worry about any of these issues. I don't think they usually affect never-used, freestanding motors because usually its carbon or rust that sticks the seals.

If the motor is out of the car and just dry, then you don't have to worry about coolant seal failure (the other bad thing that happens when motor sits too long) and the other stuff is probably ok as well, depending on the environment that the motor sat in.

But it all comes down to your compression test - you can eliminate stuck apex seals/side seal failure with a good test and save yourself some worry. If compression is good, I'd toss it in and give it a go! Like Templeton said, it is hard to check compression without being able to turn the motor over quickly, though.

I think you have nothing to worry about.
Think about the reman engines Mazda had sitting until sold.
New engine with low compression would not sell well with the public.
Would this been the case, then they would not have them built until some one needs one.

I've had personal experience with a good low hour rebuild that sat several years and ended up with zero compression, just from sitting. It certainly happens.

That's what I was afraid of

If it doesn't have good compression and the price is right. Something like that is a perfect candidate for a soft seals (and maybe springs) rebuild

It depends on how it was stored. If it was completely sealed and built with lots of assembly lube then it should be fine. The Mazda remans have every opening plugged and gobs of lube. This is how we ship out rebuilds as we know that some of the engines we build may be sitting for awhile (years) before being fired up. If the engine is sitting with the intake and exhaust open to the elements, then rust can build up inside the engine.