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blow by

J

jd40w

New User
What causes blow by?Is it bad oil rings? or bad compression rings? or both? Is there an easy fix other than engine overhaul? Thanks-smoked out in ny
 
you didnt say what engine,but you can such oil into some intakes,otherwise rings letting pressure by causes blowby.thicker oil or std can help some.
 
Blow-by is a portion the compression coming past the rings. It is a totally NORMAL thing.

Here's a picture of a brand-spankin' new $4000 engine with less than 300 hours.

All engines produce blow-by.

Allan

Blowby.JPG
 
It can be caused by mechanical wear, or even just incorrect ignition timing. Timing way out of wack can cause a lot of blowby. So can scored cylinder walls, worn piston ring grooves, etc.
Techincally, the term refers to compression getting past the rings into the crankcase. As Allan already stated, some degree of it is normal.
 
I have a IH 666 that has, I think too much blow by. In fact if I were looking for a tractor it would probably scare me off, but it uses hardly any oil and has plenty of power and starts good, so I don't worry about it.
 
Many thing can cause it and depending on what engine it can be a number of thing going wrong or even caused because it is not run as long as it needs to be or has sat for a long time. Fill in the blanks and maybe you can get an answer that will fit as far as what maybe wrong.
Bad rings or sticking rings.
Bad valve guides and or seals.
If it is a diesel maybe not running it hard enough.
Carbon build up from babying it and or not letting it get warmed up like it should . Etc. etc
 
In the case of a new or rebuilt engine, new rings take a while to seat. We had a Cat D-326 pumping water for rice production. One spring, flood waters completely submerged the engine and we had it completely rebuilt. It ran several hundred hours (24/7) with excessive blow by and oil consumption. After the rings completely seated, blow by and oil consumption were minimal.
 
"Blow by" can be simply poor quality motor oil that is vaporizing at too low a temperature. Probably not too common now, but I've seen it as late as the 80's.
 
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