Compression Testing With Engine Out

[skinner2k3 3]

I want to do a compression test on an engine that is sat in my garage, it has no oil in it and hasn’t had for some time except a bit I left in each bore.

 

Can I simply bolt on a gearbox and starter and turn it over on the deck?

 

Do I need to fill the sump with oil (all oil pipes fitted and oil cooler plate removed/filter fitted) for the test?

 

Done a search and got masses of compression test result threads!

 

Cheers

[lagonda 42]

Yes, should be able to do it like that. Lack of oil in engine not a problem if you're not actually starting it...there will be enough residual oil in the bearings.

That said, cold engine readings will not be as meaningful as those with a hot engine. Pistons, & even the liners, change shape with temperature....so an engine that is capable of nice even readings when hot might give uneven readings cold. If you're just checking for general health, blown head gasket etc, then you'll certainly et an idea if things are OK or not. Compression test won't be a complete guide even when hot....my CTi gave perfect & good compressions despite other symptoms indicative of blown head gasket. Once I removed head, I found 2 cracks in middle 2 combustin chambers....these had been opening & closing according to temperature/load/whatever....but, of course, never when I did a compression test!

Incidentally, whilst oil down the bores is a good idea, with the engine cold it will tend to mask a possible problem with worn bores/rings as far as your readings are concerned. Perhaps spraying WD40 down the bores will thin it enough to give a better idea of bore/ring wear.

Would also suggest running hot water through the engine which will raise temperature & give you more meaningful readings. Comp readings in part depend on spin speed, so it'll help there & ease "stiction" inevitable with an engine that's been standing.

Ideally you need to spin the engine over for a while with plugs out to help valves bed against any rust that may have formed on seats. My old Riley always had pathetic compressions due to this before running the engine up every five years or so.

[j_turnell 137 3 Cars]

Would deffinately put oil in it especially if its been sat for a long time! just bolt a box and starter on and put 12v to the starter, bear in mind the engine is stone cold so the results will be a bit lower than normal.

[SurGie 54]

When i searched i only found a few threads on compression test, so i started a thread on it.

 

Here might help you.

 

My engine that had been sat for 8 months or so & i got quite a good result even with it being cold, so in my experience you can get good results when the engine is cold, though it does depend on the engine and how long its been standing, ie outside etc.

 

Also seal the oil sensor hole with a sensor, as i was told it shouldn't need to because the oil wont reach that far, and seal anywhere else oil will compress and come out, seal them like you would if you were putting the engine in the car.

Edited February 23, 2010 by SurGie

[skinner2k3 3]

Thank you all, some usefull info there which I will bear in mind.

 

The engine has been kept in the garage but hasnt been run in over a year.

 

Thats a uesfull thread SurGie, one I hadnt seen before.

 

Will let you know how I get on.

 

Cheers Chaps