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No Compression
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Topic: No Compression (Read 4009 times)
March 08, 2011, 01:20:49 pm
sgeorgejr
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No Compression
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on:
March 08, 2011, 01:20:49 pm »
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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Reply #1
March 08, 2011, 01:42:30 pm
Vincent Waldon
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Re: No Compression
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Reply #1 on:
March 08, 2011, 01:42:30 pm »
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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Vince
Edmonton, Alberta, Canada
2001 silver TDI Jetta Malone Stage 1.5 , 2001 blue TDI Jetta SBIII 216s Malone Stage 3, 1970 Bay Window bus
Gone but not forgotten: 1969/1971 Beetles, 1969/1974 Westies, 1979 Rabbit, 1986 TD Jetta, 1992 gas Jetta, 1994 TD Jetta
Reply #2
March 08, 2011, 05:00:57 pm
sgeorgejr
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Re: No Compression
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Reply #2 on:
March 08, 2011, 05:00:57 pm »
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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Reply #3
March 08, 2011, 05:07:47 pm
maxfax
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Re: No Compression
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Reply #3 on:
March 08, 2011, 05:07:47 pm »
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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Reply #4
March 08, 2011, 06:55:50 pm
Quantum TD
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Re: No Compression
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Reply #4 on:
March 08, 2011, 06:55:50 pm »
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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Reply #5
March 09, 2011, 12:31:52 pm
R.O.R-2.0
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Re: No Compression
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Reply #5 on:
March 09, 2011, 12:31:52 pm »
how on earth did you CRACK/BREAK a piston?!?!?!
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Reply #6
March 09, 2011, 07:51:24 pm
sgeorgejr
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Re: No Compression
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Reply #6 on:
March 09, 2011, 07:51:24 pm »
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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Reply #7
March 09, 2011, 08:06:31 pm
maxfax
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Re: No Compression
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Reply #7 on:
March 09, 2011, 08:06:31 pm »
Were they both on the dead cylinder???
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Reply #8
March 17, 2011, 07:53:21 pm
sgeorgejr
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Re: No Compression
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Reply #8 on:
March 17, 2011, 07:53:21 pm »
yes they were. valves must have wacked the broken cylinder
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VWDiesel.net The IDI, TDI, and mTDI source.
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General Information
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Troubleshooting
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,
burn_your_money
,
Vincent Waldon
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theman53
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No Compression