Engine/Transmission (1994 - 1998) BLOWBY SMOKE - How much is too much?

[d9]

Im in the market for a second gen and have been all over test driving them like mad lately. I always pull off the oil filler cap after driving hard to check for blowby smoke.



I see at least a little smoke vapor rising out of the oil filler tube every time. So I've come to the conclusion that blowby in a diesel engine is normal.



1. IS THAT A CORRECT ASSUMPTION ??



2. SOME SMOKE SIGNIFICANTLY MORE THAN OTHERS. HOW MUCH IS TOO MUCH ?



I've searched the forum about diesel blowby -- Illflem recommended to have a diesel mechanic perform a compression test, or more simply an analysis of blowby tube exhaust gases. But for someone that is test driving vehicles left and right, are there any other simple ways (visual inspection) to objectively assess 100,000+ mile 2nd gen engine compression status?



Thanks everyone. This forum's the best.



--d9, in search of the perfect 5spd 2nd gen CTD

 

[Futures1]

Tough questions d9;

Basically, you get oil hot, you get smoke !!

If the oil is more heat tolerant, (and the engine is ok) you will get less smoke.

Ther are many variables here. An easy test for an engine/oil problem is the consumption of oil in that engine. A GOOD engine and a GOOD oil should consume very little between suggested changes.



I expect you will have more answers within a short period of time

 

[Futures1]

BTW;

100 K is not much for these engines. .

If you have your doubts about what you are looking at, I agree with "Illflem" that a check by "Certified" person might be a good idea !!

 

[illflem]

Easy way to check out what could be excessive blowby is to put your thumb over the end of the blowby at idle for a few seconds, it shouldn't blow your thumb off nor blow the dip stick out of it's tube. Never seen any specs on allowable Cummins blowby but John Deere says any more than 5 psi out the blowby indicates a valve or ring problem.

 

[RVPILOT]

blow by v/s miles

Hi miles on a highway truck a better than low miles on around the town to the market and back truck. I have been told by qualified diesel mechanics that the blow by is almost non exixtence on my 500,000 miles plus truck and quite visiable on lower milage trucks that have never left town except only accasionally. so you see that to get a lower milage truck that is this old and not many miles you can conclude that it hasn't gone anywhere. When in the old days we would buy an old gasser that was driven slowly we would take it out on the highway and blow the soot out of it and it would run better, I don't know if this applies to diesels. Stormy

 

[radixr]

Be careful about "plugging" the end of the blowby tube even with your thumb. You can pop the push rod cover gasket. Don't ask me how I know this!:{ :{