Oil Blown Out of Breathers

[Lubener]

I have been working on my old Craftsman/Roper (mid 80's) garden tractor with a B&S flat head 18HP twin engine model 422437. A lot of oil is being pushed out with great force out both breather tubes and into the air cleaner housing. So much oil that it is unusable. Oil will fill the air cleaner housing, eventually getting sucked into the carb. air horn . From there is a smoke screen out the exhaust. I am certain the oil level is not overfilled. Compression on both cylinders measure 100 psi dry. Plugs are a little carbon fouled until the intake starts sucking in the oil. Then, the plugs get coated in oil..Can there be this much blowby past rings when compression checks out at 100 psi each? There are no issues with engine sealing. Breathers are clear too. I have owned this tractor since 1986 and this issue has been getting gradually worse over time.
Any suggestions before I pull the white sheet over it for good ?

 

[Propflux01]

A stuck compression and oil control ring? Not enough to whack compression, but enough to cause blowby, since you state its been an ever-worsening issue not being regularly used. A leakdown test would be more revealing of this.

 

[oil pan 4]

Sounds like the last lawnmower engine I junked. The air filter had fallen off a some point it was given to me and I ran it till the blow by was so bad the engine would barely stay running. It puked a bunch of oil through the breather.
So that engine could have eaten a ton of dirt or have a stick ring.

 

[Lockasiam]

pull the valve covers off and check if the oil drain passage is blocked

 

[fantastic]

Make sure the simple stuff like vacuum hoses/crankcase ventilation are replaced but sounds like blowby due to age & use. Are parts still available for rebuild on something that vintage? Maybe try 50 grade oil to see if it buys anymore time (probably waste of time)?

 

[eljefino]

Could you replumb it to something akin to a road draft tube so the breathing out doesn't connect to the breathing in?

 

[jhellwig]

Rebuild or replace time. I don't know if those twins had a pcv valve like the single cylinder ones did. If it does it might be worth checking if it works.

 

[Lockasiam]

Could you replumb it to something akin to a road draft tube so the breathing out doesn't connect to the breathing in?

Where would it go

 

[Fordiesel69]

I would take the time and do a simple recheck of the hoses, breather, and then move along to a tear down. If the crankshaft is up and down (vertical crank) then in some cases these engines had aluminum cylinders. These are good for about 500 hrs if cared for. Much less if not. If you find the engine to have bare aluminum cylinders, you can run a hone thru it for 15 seconds and throw a set of ring in for a temporary soultion. Do not plan to rebuild or put much money into it. If you find it has the iron cylinder liners then it would be worth doing a rebuild as these can run for another few decades.

 

[50yr Street Mech]

Had a 1972 Briggs push mower. Garbage picked. 3hp flathead. Piston bearing rap too., and burned a little oil. ( Great pick ..Not ) This thing pushed so much oil from the breather tube, it was insane. I just plumbed it out with a hose to dump near the rear wheel ( lube the wheel while cuttin grass). Capped off carb inlet. Started running 20W50 in it. That quieted the rap and stopped the burning, not the blow-by. The higher the RPM's, the more blow-by. I should have just dug a hole and buried the whole machine. Ran it for 8 yrs like that. The engine was painted white, old engine. I beat the crap out of this thing ! Wouldn't die. Briggs don't make em like that anymore. This thing would chop thru 2' high weeds !!!!!!!!! Noisy little hot dog muffler on it. My neighbor's hated it. LOL !! Bottom line, any air cooled engine has a limited lifespan. Just plumb out the blow-by hose, cap the carb inlet, run a heavier oil. So, one day, I pushed it out for garbage pick up, with a tear in my eye Hired a landscaper to cut the grass . Got too old to be messin around withe the grass

 

[wag123]

Your engine is a "Kool Bore" aluminum cylinder engine. At 40 years old, the cylinders are just plain worn-out. Kool Bore B&S engines that are used on a regular basis will generally not last to be 40 years old. You have done good with it but the party is over, sorry.

 

[IndyIan]

Where would it go

Maybe a catch can, then dump it back in!

 

[50yr Street Mech]

Oh, a " Kool Bore"....,,,like my 1974 Chevy Vega 4 banger. I plumbed a hose from the breather and tied it up somewhere right behind the front seats. Acted like undercoating for the salty NY winters LOL Man, did that little engine shake/ rattle/ & roll. Blew out 4 qts of oil in 180 miles. I would just wait until the oil light started flickering, then add oil. I did read years later that Chevy actually did install steel sleeves in the aluminum piston bore. Could've fooled me !!! LOL But, I loved that little thing for some strange reason. Sold it for $50 bucks ... And I loved the Chevy Monza too. Another one with a junk 4 banger in it. Yeah, that old mower is part of a Kia now

 

[wag123]

I did read years later that Chevy actually did install steel sleeves in the aluminum piston bore.

No, the Vega engine never had steel sleeves installed in it. They did introduce the "Dura-Bilt" Vega engine in 1976 to address the overheating problems but it still had aluminum cylinder bores.

 

[50yr Street Mech]

Get out ! Obviously, I was reading about a different engine. WOW !!! All the way to 1976. Maybe that engineer came from Ford, who had just finished up work on the Pinto LOL...Aluminum can't handle that combustion heat. It amazes me as to what they try to get away with. Those cylinder bores must have looked like the ocean, or a really bad bondo job.....

 

[Lubener]

Your engine is a "Kool Bore" aluminum cylinder engine. At 40 years old, the cylinders are just plain worn-out. Kool Bore B&S engines that are used on a regular basis will generally not last to be 40 years old. You have done good with it but the party is over, sorry.

I see this thread has been renewed and I kind of forgot about it.

Back in March , I ended up removing both breather assemblies. The carb and intake manifold had to come off. Each breather is supposed to have a thin bakelite disc resembling a reed valve. The disc was broken on one breather and totally missing on the other. Who knows what happened to it. The breathers were long discontinued and I spent a lot of time web searching and found new parts which solved the problem. Good for another 40 years....

 

[50yr Street Mech]

Good for you ! Glad you were able to track down the parts. The only breather element I've seen on an old Briggs were those metal mesh ones, and they never go bad. That was alot of research you did to locate those parts. Best of Luck with that engine !!!!!