#3 cylinder low on compression.

[L98guy]

Lastnight I did a compression test on my 93 GSX and and all cylinders were from 170-175 except #3 which only measured 142. (done on a cold engine with oil added to cylinders). Later in the night I did a leakdown test and there was air leaking out of the dipstick tube. So is it safe to say that the rings in the #3 cylinder are messed up, or what else could be causing this? The motor has about 12,000 miles on a rebuild that used the parts listed in my profile. Any ideas suggestions would be appreciated, thanks!

 

[Mike1992]

Whats the numbers on it hot, engine without oil in the cylinders? Do that first then do it on a hot engine with a cap full of oil in each.

 

[siceclipse]

yeah thats rule #1, the engine is supposed to be at operating temps som the rings can expand a little. Are you making sure that you are at WOT when turning the engine over?

 

[johnk]

Did you have the head rebuilt professionaly? Bad valve seats will burn holes in the sides of the valves.

 

[L98guy]

I will do another comp. test tonight with the engine at operating temp and let you know what numbers I get. The head was gone through about 40,000 miles ago by the previous owner when she had the t-belt break.

 

[L98guy]

OK, I did a compression test with the motor hot and still got the same results. Anywhere from 160-165ish with #3 cylinder reading about 137-140. I added a little oil to the cylinders but didn't see any change. Also did a leakdown test again with all cylinders testing great except #3 which showed like 25% leakdown with air coming out of the dipstick tube again. So what do you guys think I should do next? Leave things the way they are and continue to drive the car or tear into it and see if I can find anything wrong? Any ideas are appreciated,Thanks.

 

[half-cocked]

Maybe valve steam seals? It's kind of odd being that air was leaking out of the dipstick tube but there was no change when you added oil during the test.