Leak Down Test Results

[blackace]

Ok I did a leak down test today and this is what I got.


1 - 38
2 - 20
3 - 28
4 - 13
5 - 8
6 - 18
7 - 25
8 - 12

All cylinders were low to moderate leakage. The only issue I had was with #1 cylinder with a reading of 38 which was the highest of all of them. Didn't find any leaks other air coming from the dipstick tube and that was with all cylinders.

So what does everyone think? Why would I be getting smoke. If I had bad rings or valve seals wouldn't the readings be higher?

 

[dusterdon]

The motor's toast. Leakdowns should be no higher than 10-12 but ideally in the 4-6 range. The air out the dipstick means bad rings. Sorry, but its time for a new motor.

don

 

[moper]

#5 isnt bad, and #8 is ok..the rest have bad rings. Sorry..

 

[blackace]

Now here is my other question. If I had bad rings wouldn't the results on the compression test be worse?


Compression test -
1 - 116
2 - 145
3 - 140
4 - 140
5 - 135
6 - 133
7 - 122
8 - 120

 

[blackace]

Also, wouldn't air be coming from the dipstick tube even if the rings were fine? You can't get a complete seal from the rings, correct?

 

[moper]

first part, no, compression readings can vary depending on wear in the timing set, camshaft, valvetrain, even a weak starter or battery can effect it. Same with vaccum leaks, wrn carb shafts, you name it.

Second part. When rings are new, there will be some leakage. after they have seated, they should leakdown in the 3-4% area. as they get tired, the walls get scored, out of round, etc, the amount they leak goes up. Keep in mind, the the leak tester is a percentage. A good cylinder that cranks 165psi, and has 4% leakage, is fine. One that cranks 120, but has 35% is pretty bad. If you cranked 135psi, but had 4% leakage, it means you may have a larger cam, or a weak starter, and the cylinder is still fine. That's why leakdowns can tell you more. They take more variables out of the equasion, so the answer is that much more concrete..