What causes blow by?

biggerred

Member
I picked up a Super M this weekend that had basically been a fence row tractor for few years. I got the old girl running today and you couldn't ask for a better running tractor but it has a lot of blow by. No smoke from the exhaust at all just smoke out the vent pipe and out of the oil fill hole. Rings, or ????
 
Yup. Rings, compounded with loose pistons. The oil ring may be somewhat OK, which is why no smoke, but with worn or relaxed rings, some of the explosion makes it's way into the crank case.

Do a compression test, dry then wet, and report your findings here.

Pete
 
Could be the rings are stuck in the pistons not allowing them to seal real well. You may get lucky and have it loosen up after operation under a good load for a bit. Otherwise, you may need to tear into it and minimally install new rings and or power cylinders. But it depends on what you are planning to do with it. Putter around at tractor shows, or work it.
 
Good thing is, new rings arent hard to install as I'm sure you know. Run it hard under load for a bit as mentioned and then see what happens.
Put good oil in it first.
 
I've had good luck with spraying Seafoam engine treatment directly into the intake on a fencerow tractor.

Get it warmed up, then spray about 1/3-1/2 of a can of the stuff directly into the intake using an old Windex bottle, as much as it will take.

Shut it down, let it cool. When you fire it up again it will smoke like a diesel for a little while, then clear right up.

Runs great, 125PSI compression, no blowby anymore.
 
That's good advice. I think also while I've got it
parked in the "next in line" shed I'll pull the plugs and
pour some tranny fluid on top of the cylinders and let
it have a good long soak before I change the oil again.
 
I forgot to ad that its a highdrum cotton tractor so its going to get treated like a trailer queen from now on.
 
If the blowby is not too bad I wonder if one of these "overhaul in a can" products would take it down to a dull roar so it wasn't too embarrassing to drive it in the tractor parade.

That is, once you've exhausted (pun intended) the other remedies.
 
Some things need analysis, this is one.
Did you change the oil?
Did you run it for an hour or so with a load (enough to say it worked)
Was the coolant at the same level when you shut it off?
Was there any coolant or water in the oil pan when drained?
Blow by with no exhaust smoke needs some hours before getting into the engine. Jim
 
(quoted from post at 03:23:30 03/31/14) I picked up a Super M this weekend that had basically been a fence row tractor for few years. I got the old girl running today and you couldn't ask for a better running tractor but it has a lot of blow by. No smoke from the exhaust at all just smoke out the vent pipe and out of the oil fill hole. Rings, or ????
could wore out valve stem seats be a cause also? Letting exhaust gas get into the valve cover on the exhaust stroke.
 
Let it soak with MMO or ATF in the cylinders. Run it under a load and see if the blowby decreases. On the ones I have seen they use oil if they have high blow by.
 
you have to change the oil, hook it to an implement, get it to operating temp then work it hard. the rings are stuck in the piston grooves and need to be forced out into the cylinders. work it for 1/2 a day then check the compression, and post it.
 
I believe that I may have found the offending cylinder causing the problem. I pulled the plugs and poured in some MMO and all held the concoction except number 4. On that one the juice went straight through. Sounds like the rings are stuck on that one. (Hopefully stuck, not broke). I'll let the oil soak in there for a few days and then run the snot out of it and see what happens.
 

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