How much blow by is normal? I have enough to make a mess of the underside of the backhoe coming out of a vent tube off the side of the crankcase. It is a 1991 Case 580K with a natural aspirated 390 CI 4 cylinder. Starts and runs great. Hasn’t been using much oil up till now. It’s due for an oil change soon.
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Engine blow by
- Thread starter Tomvarner
- Start date
Truck Shop
Senior Member
Blow-by is measured by a gauge--inches of water. But some engine manufactures don't
list a value. Just how bad is the cloud? And how many engine hours does it have?
list a value. Just how bad is the cloud? And how many engine hours does it have?
There isn’t a cloud. Just dripping oil. The engine hour meter has been disconnected since I’ve had it. You don’t want to open the fill cap with the engine running or you will get sprayed with oil droplets. If that gives you an idea of how much blow by.
Truck Shop
Senior Member
Well, the best anyone can say is--the rings are probably worn out. It's all about compression
leaking to crank case causing pressure.
leaking to crank case causing pressure.
Truck Shop
Senior Member
And-----if that is the case, normally you can see it huff on compression stroke, visible to
the {Old School Eyes}.
Georgia Iron
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I bought another motor grader with a Cummings 4bt in it. When it is running, it will spert a little bit of oil out the fill tube if the cap is off. Does not smoke once warm but does when you first start it. Seller claims smaller diesels do that. My other machine does not. I got a 5k discount on the purchase because of that. What do you guys think about a small amount of blow by.
More than likely, this machine has sat for a while because it does not look like it was used much. My other machine has much more wear in the assemblies.
I bought it as a spare for parts but it looks good enough that it could be set up to run as a second. Not sure if i should get into the engine or not
More than likely, this machine has sat for a while because it does not look like it was used much. My other machine has much more wear in the assemblies.
I bought it as a spare for parts but it looks good enough that it could be set up to run as a second. Not sure if i should get into the engine or not
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HarleyHappy
Senior Member
Could have sat for so long, the liners are pitted and the rings screwed up. As long as it stays running for what you want, everything is good.
We ain’t running Lambo’s here.
We ain’t running Lambo’s here.
Truck Shop
Senior Member
Oh no--time to reach under the mattress and spend a bunch of frog hides.
Georgia Iron
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Alright what the hell is a frog hide? Or better yet why do you call money that
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HarleyHappy
Senior Member
Frog hides and Lambo’s go hand in hand and then out the door, never to be seen again. Lol
Truck Shop
Senior Member
Because from a distance it looks like dollar bills only with legs.
Supid question time. How do you do it on a diesel? No spark plugs
No question is stupid in my world.
The injectors need to be removed and then a compression tester that has the correct fittings for a Cummins 390 is needed.
There should be a lot of information on web (YouTube) on how to do it.
Harbor Freight may have a test kit. I never have looked.
The injectors need to be removed and then a compression tester that has the correct fittings for a Cummins 390 is needed.
There should be a lot of information on web (YouTube) on how to do it.
Harbor Freight may have a test kit. I never have looked.
I was afraid of that but didn’t know. You know I never suspected low compression because of the way it fires off on the first crank. Also there’s no puffing or excessive smoke.
What should you be seeing from a good engine in respect to the fill tube blowing out oil? Does a new engine have any blow by?
I guess I’l get out the service manual and read up on injector removal.
What should you be seeing from a good engine in respect to the fill tube blowing out oil? Does a new engine have any blow by?
I guess I’l get out the service manual and read up on injector removal.
mekanik
Senior Member
Being a Case/Cummins there is probably a crankcase pressure spec and procedure in the Cummins manual.
Coaldust
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Cummins measures their base pressure specs with a blowby orifice tool with a .221" (15/64-in) outlet. Or, make your own and hook your manometer, if you are curious .
126 L/Min(10.5"rise) @ 2200rpm
152 L/Min(14.5"rise) @ 2500rpm
170 L/Min(17"rise) @ 2800 rpm
126 L/Min(10.5"rise) @ 2200rpm
152 L/Min(14.5"rise) @ 2500rpm
170 L/Min(17"rise) @ 2800 rpm
.22 LR shell with the end cut off could be the start of a redneck orifice?
Coaldust
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Good answer, Good answer. I like the way you think. I’m going to be watching you.,….
Or, a Remington .221 Fireball. That’s a blast from the past. Anyone remember that round?
Or, a Remington .221 Fireball. That’s a blast from the past. Anyone remember that round?