[CHEVY&SEARS]

I just got the GT18 running good (after several carb cleanings) and I was excited to finally cut the field. Hung the 48" on it and was able to cut in 2nd gear in tall grass no problem.

Anyways, lots of old engines puff a little smoke here and there as did this one. But it started puffing more and more. I hit a patch of thick grass and it REALLY blew smoke, almost diesel like. Oh no, something's wrong. Then smoke started coming from under the hood. Lifted the hood and shut it down.

I took the air cleaner cover off, oil everywhere. Oil was blowing out of the crankcase breather into the air cleaner box and onto the block from under the tube.

ANY ideas?

 

[mrbeef]

Gas in oil? Or was the oil coming up through the flywheel intake and just looked to be coming up the breather? Not sure how the sears tractors are laid out but we have similar problems with the Deeres sometimes.... Does it have an oil filter? Check the oil filter gasket.... It is a common problem on the 318's and 420 Deeres. Those are my guesses....

 

[CHEVY&SEARS]

Definitely not coming from intake tube because the oil is only inside the filter (where the breather comes in). No oil filter.

When I cranked it up without the airbox all assembled I noticed the crankcase breather was smoking more than normal. Maybe an early indication something was wrong.

 

[mdigby]

I'd start by cleaning out the breather tube (there should be a steel wool type filter inside) and then taking off the valve cover where the breather attaches (there is a reed valve inside.) Maybe it just needs cleaned?

The other thought is that the rings in the engine may be worn out. This could cause more pressure in the crankcase, or valve seals below the valve covers could be worn out allowing the same thing to happen.

Someone with more Onan knowledge might have other tips.

 

[mrbeef]

Hmmmmm, thinking on the fly, "several carb cleanings",... Did you change the oil after all this?

 

[edgesr]

This spring I got a SS-18 model #917-25960 with the Onan BG/MS engine. Due to a DIY remodel project and the summer heat I haven't taken much time to work on it. Did try to find if it had spark. While turning the engine over, with the breather off, I noticed there seemed to be a lot of blow back through the carb. Is this normal or should I expect the same problems that you are experiencing? I hope to get on this project soon. Also good luck on solving your problem.
Mike

 

[CHEVY&SEARS]

mdigby, the steel wool seemed fine but the reed valve is good idea. Maybe not working right. Cylinder pressure, the front cylinder is 80 PSI, Onan says down to 75 is ok.

mrbeef, The oil has been in there only a few days. The carb cleanings consisted of soaking the gas up out of the bowl and blowing out the jelly gunk that got past my crap fuel filter. (which was replaced) What would cleaning the carb do?

 

[CHEVY&SEARS]

This spring I got a SS-18 model #917-25960 with the Onan BG/MS engine. Due to a DIY remodel project and the summer heat I haven't taken much time to work on it. Did try to find if it had spark. While turning the engine over, with the breather off, I noticed there seemed to be a lot of blow back through the carb. Is this normal or should I expect the same problems that you are experiencing? I hope to get on this project soon. Also good luck on solving your problem.
Mike

If there's blow back through the carb i'd adjust the valves. I'd also clean the carb, replace intake gaskets and put a genuine Onan float in it. That's different than my problem though. Hopefully you won't have to worry about this.

 

[mrbeef]

mdigby, the steel wool seemed fine but the reed valve is good idea. Maybe not working right. Cylinder pressure, the front cylinder is 80 PSI, Onan says down to 75 is ok.

mrbeef, The oil has been in there only a few days. The carb cleanings consisted of soaking the gas up out of the bowl and blowing out the jelly gunk that got past my crap fuel filter. (which was replaced) What would cleaning the carb do?

I was in a bit of a hurry this morning when I posted that. My thought came from after you cleaned the carb the bowl was empty, depending on how you cleaned it (was not sure, aresol can while on the engine etc etc) getting the engine to fire up again may have taken several tries. Depending on the gas flow gas could have gotten into the oil or the excess carb cleaner in the oil. Overfull oil may have caused some issues with the breather.... again I am just trying to think of ideas based on some of the stuff I have run into with the Onan's I have. :fing32: Reed valve would be my next stop since that I think is the next least invasive item on the list.

 

[Tractor-Holic]

Are you using SAE 30 oil?...if the breather checks out OK and the valves are adjusted properly,it might be the oil is getting diluted or breaking down at high temps and losing viscosity...multi-weights often get too thin at high temps and will engourage excess blow by...it is possible for oil control rings to get stuck or loaded with carbon and let excess blow by get into the combustion chamber,but the compression rings will still seal well enough to provide good compression readings..

For the time being if the breather seems ok and the valves aren't out of adjustment,adding some STP or Lucas might help reduce the blow by ..it might get better by itself after some use if the oil rings were sticking or clogged up with gunk..

 

[CHEVY&SEARS]

Which one of these is correct? The black oily one is from the GT18.

Here's how the valve was when I took it apart. Looks like it does in the manual.

mrbeef, I checked the oil no gas.

TH, I am using SAE 30. Breather and valves are good.

 

[boomers_influence]

chevy
i see you only listed one side for compression.
if one cylinder has EXCESSIVE blow by the
breather will not handle it all.
please check both sides.
over the years the mesh was made of copper or stainless steel.
is it poss. that the foreign piece in the top R.H. of the
pic. ended blocking the small oil return hole in the cover?
thank you. boomer

 

[78SearsLoader]

I had this problem with my b48m and it ended up knocking i took the oil pan off to find the oil pump was clogged completly full with what looked like paper towels

 

[CHEVY&SEARS]

After I put the valve cover back and put the pack/mesh from the SS18 (the drier of the 2 in the previous picture) on today. I cranked it up to see what would happen. Seemed fine. So I preceded to cut the rest of the grass (same amount of time as yesterday) with no problems. None. And boy is it powerful...

Boomer, the rear cylinder is 90 PSI. Is the mesh cleanable? Should it be cleaned? I think the drain hole was covered like you said. Thanks.

78, hope it doesn't start knocking.

 

[mrbeef]

Good to hear. I learn a little more about Onans.:fing32:

 

[Plowthesidewalk]

Glad to hear it is running again. Whew!

 

[tomw0]

With as much 'stuff' in the mesh and gunk in the breather valve area, I'd expect a good cleaning would improve things a lot. The mesh can be cleaned without problems if it is metal. Use brake clean or carb cleaner or even detergent, but make sure to leave none of that behind, and bake it in the sun before re-installation so you don't contaminate the oil.
The purpose is to snag any oil droplets or vapor that has oil in quantity, and make it run into the snarl of fiber, metal or other, and deposit there. The 'vapor' will go around corners in the fiber mess, but any droplets will want to go straight, and will run into fiber or metal, and land there. After enough deposits, it will form a drop, and trickle down to the bottom of the box, and leak back into the sump.
If it were mine, I would clean the valve, spring, retainer and cover, and make a new gasket. It doesn't have to be spotless, but you don't want meandering crud to prop the valve open or plug the drain.
tom

 

[CHEVY&SEARS]

Thanks. You're right, I do need to do a good cleaning. The whole top of the block needs a good cleaning because of all the oil that spilled on it but the grass needed to be cut.

 

[AngieK]

Boomer,

I don't have the breather tube filter in my BG/MS in the SS/18, how important is it to have it in place? It was missing when I got the tractor and until just now I didn't realize it was supposed to have one. :dunno:

"Grandad" smokes a little bit, but I assumed it was because I have to run him with a bit of choke on. The throttle lever seems to be an "all or nothing" proposition, so generally if I don't want the revs I just use a little choke to putt around the yard.

 

[boomers_influence]

angie
it is very important to have the
breather tube and the mesh that
is inside it.
i will send you a p.m.
thank you boomer