VWDiesel.net The IDI, TDI, and mTDI source.
General Information => Troubleshooting => Topic started by: sgeorgejr on March 08, 2011, 10:20:49 am
-
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?
-
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!
-
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.
-
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??
-
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.
-
how on earth did you CRACK/BREAK a piston?!?!?! :o
-
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.
-
Were they both on the dead cylinder???
-
yes they were. valves must have wacked the broken cylinder