Compression Test

[Tom Bond]

Would it be to my benefit at all to do a compression test before I pull my cylinder head to help me diagnose any other issues? Don't currently have a test kit but as I get more into these old timers, I figure I might need one somewhere along the line. Was going to check out Northern Tool and run over to the local Sears to see what they offer.
 

[souNdguy]

by all means DO perform a comp test / wet-dry BEFORE cracking the head. once you crack the head.. your empirical data is lost.

toooo mannnny people rip the head off before doing some practical observation.

now.. whether the comp tests actually help with your particular situation remains to be seen without more info ont he issue.. however it never hurts to know a before #
 

[old]

You would probably be better of doing a leak down test instead of a compression test. By doing the leak down you would find which cylinder has the bad gasket area or crack in the head etc.
 

[souNdguy]

do both.. more tests the better..
 

[old]

Very true plus with a leak down test you can maybe see bubbles in the cooling system that you may not see by doing the compression test.
 

[Tom Bond]

Already spotted the bubbles in the radiator along with some tan milky oil in the crank case. Thats whats leaning me towards the headgasket. (hopefully thats all) Have a gearhead at the shop lending me a compression tester to do a dry/wet test.
 

[old]

Gear head so is that what you call us guys who try to help you??? As for the bubbles in the radiator a leak down test would tell you which cylinder the bubbles come from so you then know where to better look for cracks and all if you do not see for sure a blown head gasket. By the way just giving you a hard time on the gear head thing since back when I was in High school I never took any shop classes
 

[Tom Bond]

hahahahah. I hear you Old. Just a figure of speech. I'm thinking of investing in a leak down test. Me and the "gearhead" figure between the 2 of us, him with a compression tester and me with a leak down tester, we could narrow problems down much more precisely. First things first though. The compression test and see what the #'s look like. I'll post them sometime next week when I get the tests done.
 

[old]

When I was in high school I was more of the science nerd type doing the electronics stuff and the chemical stuff. Still wish I could find some sulfur and some salt peter on bulk by the way. But then in the navy I went the other way and was teaching guys how to keep there cars running and doing engine rebuilds and I was an electronics technician then
 

[john in la]

A leak down tester requires a air compressor to use it and some do not have that ability. It will also confirm a blown head gasket by showing bubbles in the radiator that way you can get pump cavitation out of the possible source of bubbles you saw already.
If you do not want to spend the money on a one time use for a leak down tester you can buy a replacement hose for a leak down tester and use it to shoot air into the cylinder. This will not show leak down but will pressurize the cylinder so you can see if bubbles appear in the radiator.

While a compression test will show what cylinder is bad it does not narrow down the possible causes. This is where a leak down test comes in. Applying air to the cylinder lets you know if it is a head gasket (bubbles in radiator) an exhaust/intake valve (hissing air in tail pipe or intake) or a bad piston/rings (pressure in crankcase)

With all that said I really do not think you need a leak down test. We already know if the compression test shows a bad cylinder it is most likely going to be a head gasket or a cracked head because bubbles in radiator have been seen.
 

[john in la]

"You would probably be better of doing a leak down test instead of a compression test. By doing the leak down you would find which cylinder has the bad gasket area or crack in the head etc."

Maybe I am reading this wrong but it sure seems to me you are trying to say he should do a leak down test because a compression test will NOT show him what cylinder is bad.

"As for the bubbles in the radiator a leak down test would tell you which cylinder the bubbles come from so you then know where to better look for cracks"

There it is again. Use a leak down test to find the cylinder with the problem.

You do not really think a leak down test is any better than a compression test at pinpointing a problem in a cylinder and telling you what cylinder the problem is in. DO YOU???????????
 

[old]

Yes I do since a leak down test compresses air into each cylinder r one at a time so then you watch a gauge to see which cylinder will not hold compression over X number of minutes and in doing so you can watch the radiator for air/bubbles. As in you charge the cylinder up to X number of PSI and see where you loose the PSI and how fast
 

[souNdguy]

you can make a cyl adapter with an old spark plug and an air fitting.

bust the insulator out and remov ethe electrodes.. and then solder/braze/weld a male qd on it. perhaps an angle fitting first if planned to use on an N.. coud weld on a female threaded 90 and then just screw inthe male qd air adapter.. etc.

poor mans leak tester. then just about any air pump or air up tank will work for ya.,
 

[Hobo,NC]

All you need to do is pressurize each cylinder with air regulated @100 PSI are less NO MORE)

The other test are not a waist of time but probably will not help locate a leak that does not affect performance... The pressure difference will most likely be to small on a engine that runs good...

Normally the first thing I would do is pressurize the cooling system with plugs removed... Are remove the plugs over night and look in each hole the next day for coolant and do a spin test and look for coolant spiting out a plug hole either in liquid are vapor form...

NOW WHY,,, so I know were to considerate my efforts once I remove the head..
I normally am dealing with a leak of this type on a engine less than 10 years old so the head gasket has not aged out,, the time and parts money required for a lets take as guess is 10 times are more than on your tractor...

Old tractors,,, for the record head gaskets do not last forever you may find it leaking on all cylinders if so that's a good thing replace the gasket its served its time... If this is the case normally a re-torque will resolve the issue that tells you to replace the gasket its served its time and on the way out...
 

[Tom Bond]

After all the suggestions and odds are, I'll only be using a leak down tester on rare occasions, I decided to save myself about $100 and use SoundGuys idea and build a poor mans tester. I'll just pressurize each cyclinder and diagnose from there. I took a couple different spark plugs and gutted them out, then silver soldered on a male air chuck to each. Added an "O"ring and ready to go. I'll let the air compressor cycle off and bring up the regulator slowly to 100# and listen for leaks or watch for bubbles in the radiator. Here's what they look like.