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Old 06-15-2021, 06:13 PM   #80
ecp
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Join Date: Sep 2020
Location: Georgia
Posts: 98
Quote:
Originally Posted by ike84 View Post
At tdc, both intake and exhaust valves should be closed. Hence, whatever pressure you put in should stay there. Even in a small space, 25psi is a lot of air. If you aren't getting it back there is a problem. You are effectively doing a poor man's leak down test, but I don't think you're gonna get any kind of good diagnostic data with the way you're doing it. You said the dealership did a leak down - what did it show?

The bottom line here is that if a cylinder won't pressurize, or won't hold pressure, you have a serious problem.

One caveat there - we have low pressure piston rings. So, in the absence of a crank case vacuum, expect some leak down. Not complete loss though.



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Poor mans leakdown yes. I have the cams out on bank one so all the valves are closed. The boxes of suspension parts sitting in my house drained me dry, and then this happened. I know it’s not the best or anywhere near precise, but it would give me a yes/no answer if wether there was pressure building or not.
I’m gonna give them a call tomorrow. They did perform a leak down and borescope but only mentioned the one valve that was open, which i was able to diagnose as the busted spring. I know the motor isn’t perfect. It sat for about two years and given the state it was in when i bought it, definitely neglected. that’s why i don’t want to put major money into a repair of a neglected engine with 124k miles. would rather put in a new or nice used one in the future.

I did have my buddy with a good borescope come by, we didn’t see anything. in cyl one it was hard to see with it being at tdc, but i didn’t want to rotate the engine with the cams out. But it’s not like we saw glitter or a big hole in the piston, just normal carbon buildup on it. Just wishing i put the compression tester on cyl one when i did cyl two....
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