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Discussion Starter #1
I did a compression test on my 93 Bronco with a 5.0L in it. I did the test because i have some oil coming out of the PCV breather. The engine has approx. 190,000 miles on it according to the odometer. Tested the cylinders starting on the front passenger side, moving to the back. Then moving to the front driver side, then moving to the back.

1- 178
2- 180
3- 170
4- 175
5- 182
6- 181
7- 179
8- 60 (80 when put oil in cylinder)

I am assuming that it is a worn ring in cylinder 8. Just wanted to get other peoples input. Also the spark plug in 8 had a good amount of carbon buildup on it while the others were fairly clean. Thanks
 

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Probably time to take it apart and rebuild or a engine swap. The carbon buildup on the plug is very likely from burning oil. Which usually comes from valve seals or piston rings being worn. The slight increase in compression does indicate the rings are not doing to good. A leak down test would show you exactly where the compression is leaking from.
 

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Satyr of the Midwest
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17,734 Posts
There is a TSB regarding this, but the failure is most likely due to the PCV system routing. We've covered it here on FSB, and there is a thread dedicated to the topic. In a nutshell, the PCV inlet must be re-routed to the middle of the intake plenum, i.e. where the power brake booster vacuum line is connected. You can effectively swap the two lines, and you only need a couple lengths of PCV hose to do it. DO NOT use regular 'vacuum line', as the oil in the system will destroy it.

To answer your question, a rebuild is required with that low pressure on #8. Unfortunate, but not surprising.
 
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