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I have a Opel Corsa 1999 B type. We had a mechanic redo the engine about 4 months ago, but this week it just does not want to start.

Today had other mechanic look at the engine, and did a quick compression test, cyclinder 1 and 4 where under the normal presure. Those cylinders where running under pressure before the engine was redone.

For a while now the engine has not been running at its best, it idelled under its normal revs and you really had to put your foot down to get some kid of preformance.

Also checked the spark plugs, All are black, and cylinder 4's spark plug has oil on it.

So what could cause the low compression so, soon after the engine has been redone?

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How many kilometers on the engine? What was redone? Were the rings replaced and the cylinders honed? Were the valve seals replaced? Were valves lapped or replaced? By redone, do you mean the timing belt was changed? What does redone mean in this context? –  ferrunner Sep 8 '12 at 20:33
    
Over 200 000km, replace the valves and reset them, skim the top, drill the block, new oversize pistols with new oversize rings. New bearings mains, and big ends. And new water pump, new water bump, new timing melt, and put in second hand injectors, and full gasket set. –  ZioN Sep 10 '12 at 14:55
    
Was the engine broken in properly after being rebuilt? What was the compression right after the rebuild? –  Nick Sep 10 '12 at 20:45
    
We did not test the compression afterwards, we should have, but it did not idle right after the engine was rebuilt. Also our mechanic told us after he put the engine together, took it out for a test drive, and drove it quite hard. He said that it's fine, don't need to broke it in. Now I am wondering if this maybe was not the cause of all of this. –  ZioN Sep 11 '12 at 5:08
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3 Answers

Oil on the spark plug is likely either because the piston rings are not sealing or the valve guides are leaking oil. Both could also be related to low compression. You could either have ring seal problems or a valve that is not seating properly. Valve seat problems could be due to physical damage or carbon build-up coming loose. Guess at what is most likely depends on what was done when the engine was last worked on.

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I've learned of two possible causes:

  1. Typically the valves at the exhaust side can where out and compression can "leak"
  2. Also there can be a break in the cylinder where the compression escapes

Are these possible in your case?

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Why was it redone? And was your block checked for warping? If it was warped, and not corrected, you could be facing the same problem.

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The engine was redone, because the engine was running bad, it was making a winding sound, and you had to rev the engine high to get the car moving. And the block was not checked if it was warped. Did not even know that was possible. –  ZioN Sep 11 '12 at 5:12
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