How to check if rings are wore?

[Dan Hill]

From a professional diesel tech. Diesel is all about compression, heat, and fuel at the proper time. If it starts well in cooler temps, say 50-60 ish, it should be fine. Don't overthink what "may" be wrong. Starts good and power is there, run it! BTW, all diesels turn their lube oil black within no time, which is completely normal. Use quality oil and maintain the level and she will be a happy lil thumper. Good luck!

 

[Charles Erwin]

Robert - Your approach is logical. If the symptoms you describe - oil out the dipstick - happen at idle speed the crankcase is clearly overpressure and compression rings are the probable culprit. However, that does not necessarlly implicate comprehensive compression ring seal failure. Excessive oil consumption can be caused by a blocked crankcase vent in which case normal "blowby" pressure cannot be released to the intake manifold. But in that case you would not notice oiil discharge via the dipstick at idle speed. As for valve stem seal failure, it is impossible to diagnose failed valve stem seals by estimating flow via the oil fill cap. Stem seal failure is a matter of oil being drawn past the valve stem seal into the cumbustion chamber when the piston is on the the intake stroke. The oil fill cap has a clear path to the crankcase thus normal crankcase pressure will completely overcome stem seal vacuum. The only flaw I see in your logic is that that these symptoms - even if the compression rings no longer seal - will be nearly impossible to detect at idle speed. The short of it is that you can have excessive oil consumption due to stem seal failure but you will not be able to detect (nor probably even measure) vacuum or pressure differences that can verify stem seal failure. In other words stem seal failure results in increased oil consumption - without any additional symptoms. You can have oil consumption due to failed compression rings- obvioulsy - but you can have excessive consumption even where the compression rings are not compromised if the ventilation system is jammed full open thus oil is drawn into the manifold. You can have consumption when the ventilation system is blocked, thus causing oil degradation, thus causing the oil control ring seal to become degraded by accumulated debris - thus they no longer work. When oil control rings no longer seal they cannot return oil to the sump. An actual physical measurement of crankcase pressure and intake manifold vacuum can be helpful. However, apart from comprehensive failure of compression ring seal - it is not possible to diagnose excessive oil by feel even in the relatively extreme wear case - because these things are not likely to show up at idle speed. Too much info maybe? Hope not - just want everyone to think the matter through.

Boy -- I hope the OP has solved his problem because we are a bit off his question.

Charles

 

[Ken13559]

Well looks like I've many posts to digest and Bill the RCA dog looks just fine.
For the record, whenever I changed oil, I'm able to extract at least 1.5 litre. That one time, I managed to extract only 1/2 litre. I know there's residual oil and it has always been that way. After filling the normal almost 2litre the engine ran just fine. I'm just concern that the rings might have been wore due to low oil level for many hours.
Is there a diesel compression meter/gauge for Yanmar that I can buy via internet? Thanks.

Charles, concern of wear is still there although haven't seen any problem with engine (or not fully aware if there's any problem for now). Interesting discussions.

 

[Charles Erwin]

Ken-
Check the oil level each day in the AM and top up as necessary. Yanmar wants to see the crankcase kept to the full mark so keep it topped up. Keep a log of oil use - how much you add - from now to the next 100 hr - thus to keep track of oil consumpiton. Change the oil at 100 hour intervals - olil filter too. Consider verifying the breather is clear - annually is plenty often - just to keep the cranckcase ventilated. If constant rate oil consumption - then no worries.
As to a compression tester check with Yanmar or any other service person and they will tell you where you can obtain one that will work for your motor. They are not all that convienient to use.
If you hurt the motor from lack of oil - I doubt rings would be the first thing to give up.
Since you had no low oil pressure alarm - ie the oil pressure gauge never went to 0 - I doubt there is anything to this.
Bill?
Charles

 

[kloudie1]

Ken, it doesn't sound broken.. don't fix it ! now that ya know it uses a bit of oil, check it every day of motoring and refill as necessary

 

[Ken13559]

"If it ain't broken, don't fix it". Will monitor oil consumption with each use. Okie dokie.