compression/leakdown test question
Thread Starter
Pro
Joined: Aug 2005
Posts: 627
Likes: 1
From: Naperville IL
compression/leakdown test question
I just bought a compression guage and am planning to make some kind of leakdown guage sometime soon as well, but I noticed the directions on the compression tester say to get the engine up to operating temperature prior to testing. Now this makes sense as I can see how cold metal parts would would have different tolerances than hot metal parts, but I'm not crazy about the idea of pulling spark plugs and running rubber hoses next to hot exhaust manifolds. How much will my numbers be off if I test it cold?
Melting Slicks
Joined: Sep 2000
Posts: 2,401
Likes: 416
From: Chester Virginia
The compression test is a relative test not definitive test. You are checking one cylinder verus the other cylinders. As long as the numbers are within 10%-15% of each other you re in good shape. The leakdown test will give you more of a actual percentage. Again you are still looking at the percentages being about the same. Unless the percentages are really low the actual number is that critical for a street driver. I did my '73 last spring after a valve spring broke. Needless to stay the tests were down with a cold engine. After the valves were replaced and I ran it for a few days then I checked two easy to get two cylinders. I saw little difference in the numbers for either test; less than 10 in the compression test and less than 5 in th eleak down test.
Roger
Roger
