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Extremely low compression on one cylinder from dry test

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93 Loyale

 

I found one cylinder with extremely low compression - So far I have read that the cause could be rings or an exhaust valve.

 

Here are the dry compression test results:

 

150

150

145

40 (pass side near firewall)

 

The results of a 'wet' compression test should tell me if it is the ring(s) or perhaps a valve issue, correct? How much oil should I put down the hole for the wet test? Anything else I should look for when I take the head off again? It didn't look cracked when I had it off to do the HG's.

Just a couple squirts of oil from an oil can - but yeah it sounds like an exhaust valve issue to me from the number. That's a lot of blow-by and rings would not be suspect with an engine that doesn't burn a TON of oil and in any case you have good numbers for the other three which typically indicates properly sealing rings and good maintenance - almost certainly a valve job.

 

GD

  • Author

Great news, thanks GD!

 

Yes it doesn't burn any oil from what I can tell. It is the same engine that I have been suspecting and trying to diagnose a possible partially blocked exhaust on. After 10 or 20 minutes of driving she puffs a cloud of smoke and soils the air cleaner with a bunch of oil, even after a fully cleaned (with pipe cleaners, solvent and compressed air) PCV route.

 

The maintenance records are freakishly in order and documented quarterly in the owners manual up to about 10,000 km ago.

 

Is it possible that this leaking exhaust valve could be what I was mistaking for a partially blocked exhaust?

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