Checking compression

[NCScott]

HI Guys

I just got a tractor that hasn"t run in 5-6 years. I want to check the compression, so my question is do I put some ATF in there since it hasn"t run in a while? If so, wouldn"t that affect the compression numbers?

Thanks for the help!

Scott

 

[Bruce (VA)]

You add ATF or MMO to each cylinder as it will unstick the rings. And, it adds a bit of lubrication. Do not attempt to turn the engine over. You could break the rings if they are rusted to the cylinder walls. Pull all plugs, add a tablespoon or so of ATF or MMO in each cylinder. Pull both valve covers & soak everything w/ MMO or ATF. Remove the 15/16 hex nut to the right of the water pump. This is where your oil gallery is for the valves/lifters is. Don't lose the little spring under the nut. Use an oil squirt can to put about a cup of oil in here. Replace the spring & nut. Then, start looking for mouse/hornet nests in places like the tail pipe & carb breather hose. Wait at least 2 or 3 days before you do anything, then try & hand crank the engine. (w/o spark plugs) If it does not turn by hand, repeat everything you just did, ie, more MMO or ATF. If it still won’t turn by hand, remove the starter (see tip # 36) and use a BF screwdriver or jack handle on the ring gear teeth to try & turn it over.
50 Tips

 

[Dell (WA)]

Scott......what Bruce sez......and..... Normally you take 2-compression readings. Dry and then WET. Ford specs; 90psi minimum (DRY) and then a WET reading that will evaluate the ring wear. A new rebuilt engine will test about 125psi (dry) and surprizingly enuff, about 130psi (wet) A good runnin' N-Engine will test about 110psi (dry) and about 120psi (wet) A well worn engine will test 100psi (dry) and maybe 120psi (wet) Iff'n you gitt NO increase in compression WET, you probably have BURNED exhaust valve. Surprizingly enuff, intake valves NEVER burn. You gitt 60-70psi reading, blown headgasket.

Would it surprize you to learn that compression gauges usually come with "instructions"??? .......Dell the compressed

 

[Hobo,NC]

Oil'er down no need for a dry test at this time... don't waist your time scrubbing the valves till you know you need to go their ,its a waist of time anyways but turns some folks on... I think it charges their batteries... Dunno I can think of better ways...

60/70 PSI reading does not mean you have a blown head gasket... It means you need to do another test that's a little more than most can compered...

A compression test is just one link in diagnosing cylinder efficiency... It either tells ya you are good to go are you need to go farther in your diagnosis... It would be rare a compression test would identify/pinpoint the culprit...