No engine cylinder compression

Tiny
ELTAZ
  • MEMBER
  • 1991 CHEVROLET 1500
  • 4.3L
  • 6 CYL
  • 2WD
  • MANUAL
  • 250,000 MILES
Just replaced head gasket due to overheating. Heads had valve seats replaced 60,000 miles ago. I replaced the head gasket and cleaned up the engine 9 years ago, and it ran perfectly. This time, I took to machine shop and both heads shaved and checked for cracks and leaks. Compression was at high levels prior to gasket replacement. Cylinder #5 where head gasket became damaged, radiator fluid filled the cylinder. After replacing with new head gasket, valves were adjusted per manual, valve lash removed and turned 1 full turn to tighten. New head bolts torqued per manual. When engine would not start, checked for fuel and spark, both good, but compression results on both sides was 0 (zero). Hmm? Any ideas on what and how to check for the compression leak?
Monday, March 23rd, 2020 AT 7:17 PM

3 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
You need to run a cylinder leakage test or leak down test. Here is a video that gives a pretty good walk through:

https://youtu.be/WHli-wLy9_o

Having 0 compression I would suspect you have a valve hanging open or the head is warped. How bad was the overheat? I understand they cut the heads but did they straight edge them? This is pretty typical so I am sure they did but it would be worth a phone call to make sure they can give you a number which shows they measured it.

Let us know what you find. Thanks
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Monday, March 23rd, 2020 AT 7:40 PM
Tiny
ELTAZ
  • MEMBER
  • 2 POSTS
Hello KASEKENNY1, I completed a cylinder leak test and I followed the air sounds. Turns out the valves were too tight, which kept the valves from closing completely. I had followed the manual, but found out I needed to just barley remove lash and tighten 1/4 turn. Then, I checked each cylinder for compression and most were still too tight, so I turned back each valve bolt until I measured proper compression, which was better than before, albeit, new head gasket. All cylinder valves were readjusted for compression. Truck started immediately and ran awesomely powerful. No tappet sounds, nice and quiet. Thank you for your help!
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Wednesday, April 1st, 2020 AT 12:55 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
That is an excellent update. Thanks for providing that and good work. Thanks for using 2CarPros. Please come back next time. Thanks
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Thursday, April 2nd, 2020 AT 4:03 PM

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