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No Compression
by
sgeorgejr
on 08 Mar, 2011 13:20
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Need help diagnosing. I just bored my 1.6 diesel and replaced it with a 1.0 mm oversized pistons. The car ran but was smoking a lot after the rebuild. After compression check, 1,2,3 had almost 400psi and 4 had 0. The pistons are brand new. I am suspecting a bent valve, but by eye, they look ok. The old piston broke on the old engine, so that is why it needed a boring/rebuild. is there anything i am missing?
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#1
by
Vincent Waldon
on 08 Mar, 2011 13:42
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On a fresh engine some smoke is very normal... sometimes they smoke quite a bit.
A couple of questions:
- is the hole with the low compression the same hole that broke the piston the last time??
- was there any headwork performed while you had the engine apart?
- did you seat the rings during the first 20 minutes of run-time?
A valve that's not seating or some broken rings in #4 would account for low compression.. although 0 is really low!
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#2
by
sgeorgejr
on 08 Mar, 2011 17:00
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Thanks for the reply,
The no compression was the same as the one which broke the piston, and i did not perform any head work (although i just sent it out today to get checked). I did not reset the piston rings. The car did not run for over 20 minutes.
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#3
by
maxfax
on 08 Mar, 2011 17:07
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I'd bet one of your valves on that cyl is tweaked a bit.. Just eyeballing them they can look fine, but not be perfectly sealed..
0 compression is impressively low..Did you notice an odd "hissing" sound from the exhaust or intake when cranking or running??
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#4
by
Quantum TD
on 08 Mar, 2011 18:55
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If you had done valve work, I would have guessed that your valve shims were too thick. But since you didn't, I'm guessing everyone else is on track with bent valve.
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#5
by
R.O.R-2.0
on 09 Mar, 2011 12:31
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how on earth did you CRACK/BREAK a piston?!?!?!
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#6
by
sgeorgejr
on 09 Mar, 2011 19:51
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2 bent valves......thanks for the replies. I didnt break the piston, the last owner did. not sure what happened, but it was mine to fix for $400 so i took the chance.
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#7
by
maxfax
on 09 Mar, 2011 20:06
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Were they both on the dead cylinder???
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#8
by
sgeorgejr
on 17 Mar, 2011 19:53
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yes they were. valves must have wacked the broken cylinder