lets talk about blo-by

[5020s rock]

hello--somthings been buggin me--blo-by or
valve cover exhaust on new gen tractors. i always thought a large volume of "smoke" from these tubes was a negative. i have since seen
worn-out, used up tractors with minor blo-by and recently overhauled tractors with major blo-by.
at 43 yrs old i am changing my thinking.....any input??

 

[Aaron Ford]

I am right there with ya. If mine started it I would have a wrench set in my hand. I have seen blowby issues on a higher mile turbodiesel. So new tractors have it?

Aaron

 

[Bob]

Any of the new-gens still equipped with a functioning crankcase ventilation pump will appear to have lots of blowby 'cause the vent pump is pulling in clean air after the aircleaner an forcing it into the crankcase, pushing the fumes out the breather.

 

[dpurvis1]

i would think a vetilater pump would draw fumes from the crankcase not blow into crankcase. blowby has to come from cumbustion gasses past rings, all engines have some blowby, but if excessive has to be worn ring"s/cylinders or possibly ventilater not working at all or passage plugged.

 

[Bob]

depurvis...

You wrote "i would think a vetilater pump would draw fumes from the crankcase not blow into crankcase."

You may THINK that all you want too, but it's NOT how the DEERE engineers saw things.

The way they set it up, the crankcase vent pump BLOWS air filtered by the engine air cleaner INTO the crankcase, and it EXITS through the breather tube to the atmosphere,

 

[dpurvis1]

you may be right, but even if it does if there was no blowby you couldn"t see it coming out the tube because it would be clean air. i still say some blowby is normal, but if it"s heavy it"s not normal. iv"e got a 4010 now and have had a 3020 and a 4020 all diesels and none had much blowby. i"m thinking the later one"s didn"t have the vent pump.

 

[gtx1967jewison]

every modern diesel (post 1960) i have ever seen of any brand, has a vent pump. even with no real blowby to speak of you WILL still see lots of vapor coming out the vent tube, especially in cool or humid weather. this is because of the warm temps inside & condensation etc. much of what you see is simply moisture. the only style ive ever seen, they all pressurize rather than suck. this is so that when/if excessive blowby occurs, it still all gets expelled/ flushed. if you were only sucking, the blowby would easily exceed the volume capacity of the pump under high load.

 

[5020s rock]

well that helps.....a little. my old thinking was like dpurvis, the rings are worn thus causing more volume. my new thinking is its ok....becuz you guys said so.

 

[Tx Jim]

(quoted from post at 21:09:27 12/16/10) every modern diesel (post 1960) i have ever seen of any brand, has a vent pump.

My '91 JD 4255,'78 Ford 6700 & 2000 model M4900 diesels don't have a crankcase vent pump. JD 3010/4010 & early 4020/3020's had vent pumps through the model years 1968. Side console 3020/4020 didn't have one.

JD rep's suggested plugging the vent pumps on early models.

 

[dpurvis1]

i know both bob and tx jim know what they are talking about. but if you have an old tractor that puts out little crankcase vapors and a recent rebuild that has major blowby the cylinders are not sealing as good as the old one. again some blowby is normal as there is no perfect sealing rings, some are better than others. blowby only comes from cylinder leakage.
my theory is if the tractor starts and runs good for you and doesn't use or blow oil out don't worry about it

 

[Tx Jim]

The JD 4255 I have shows 10,302 hrs on the speed/hour meter. It has some blow-by but it only uses 4 to 5 qts of oil between regular 200 hr(recommended by operators manual) oil changes. It still has enough power to pull my rd hay baler so I will keep running it as it is.
BTW it's had the JD recommended under-haul.