My first leak down test w/results -

[fallingat120mph]

1986 with 200,000 miles on it.

Broken head stud and some oil leaks is where I am now...oil leak looks like a bad seated oil return tube I installed and will be addressed.

Being a long weekend I wanted to break out my new OTC Cylinder Leakage Tester.

So, after taking the 911 up the highway getting it warmed up performed the test...

My results (at 80psi) were: ((pretty sure the math is right))

----------------------------------
#1 76 5%
#6 76 5%
#2 76 5%
#4 72 10%
#3 76 5%
#5 71 11% (was 72 on second test)


The biggest issue was being in Texas and trying to single out where I was hearing any air being forced out - the fireworks have started and it is 100 degrees in the garage - so may repeat in the quiet hours of the early morning.

Also, the car has been sitting for a month or so and tried to take it out to get warmed up but I am still nervous taking plugs out/putting plugs in a very hot engine. Not sure I got the engine hot enough...?

The broken head stud is the major issue and don't think these numbers look too bad?

It seems I might need to get out and drive it hard, since it's been sitting - Italian tune up as some of you say...and then check again.

Any input or opinions are appreciated. Just curious if these numbers are a major concern on a car with 200,000 miles on it. Trying to learn as much as I can before I drop the engine to address the head stud issue this fall...


Thanks!
Erik

[rswannabe]

The math is a lot easier if you up the intake pressure on the leakdown gauge to 100 psi. That will also make it easier to hear the leaks.

[dannobee]

The 80psi thing is commonly used in aircraft (ie 76/80). Us automotive guys use 100 and read the leakage percentage directly.

[rswannabe]

Cylinders 4 and 5 are the only ones low enough to be concerning, but they are not horrible. Barring other problems with the motor, I’d just keep driving and enjoying it.

[fallingat120mph]

Thanks for the responses. I really thought I might have issues with the broken head stud - which is on the driver side, so the side of 1,2,and 3. And those seem to be fine at this point.

Not quite sure that one can effect the other...

Overall, with 200,000 miles am quite happy - but feel some things need to be addressed sooner then later.

Side note:
I was always under the impression of using 80psi (perhaps 90) was the proper number. If a lot of you are using 100psi and that is a better process I would like to know. I understand the math is easier and see the point being able to 'hear the leaks'...


Thanks!

[fallingat120mph]

Also...a broken head stud has been an eye opener, and new to me after all these years of ownership.

My question would be is a leak down test something as an owner I should do annually? Every valve adjustment? etc...


Thanks -
Erik

[Tinker]

With that mileage, I'd just drive it and keep and ear out for rattling which will be the top of the cylinder dancing on the head. And start saving for a rebuild.
Wouldn't hurt to check the leak down numbers upon adjusting the valves and keep an eye on the mating surfaces of the head and cylinders for leaks.

Tinker