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B&S 18 HP oil leak

14 years ago

Model No. 42A707. Oil is leaking from under left side where the cylinder meets the crank case. I thought is was a bad gasket between the cyliner and the crank case but from what It looks like is the cylinder is part of the crank case and does not bolt together. Is there a valve adjustment access or something in that area that could be the source of the oil leakage? and how is the best way to get to it?

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Comments (6)

a-c_homesteader
14 years ago
Try replacing the gasket between the block and the pan
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tomplum
14 years ago
Two other things to watch for: 1) If the oil drain is on that side make sure it is secure. Also, the engine has a rear cover (4 bolts) that sometimes leaks.
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That is unfortunate. If the carb had an internal leak, the fuel that went into the crankcase remains and certainly doesn't help the oil do its job. The reverse is true in fact. The fuel part that is in the oil if small will vent itself out first, but there is the thinning of the oil which is reducing the oils effectiveness. There could be oil loss / pressure building from a head gasket failure- but it goes back to how long this engine has been running w/ fuel in the crankcase and what the correct repair really is. If were talking a couple on 10 minute periods of use nbd, but running long periods of time- you want to push for engine replacement. you will also want to know that there is no debris in the tank that caused the whole thing in the first place.
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I did not read where you had changed the crankcase oil after the new carb was put on. If the old carb had been leaking there would certainly have been a quantity of gasoline in the crankcase oil. What happens is that when the engine is started with gasoline in the crankcase oil, after the engine begins to get warm........the gasoline begins to boil out of the oil. The evaporated gasoline then vents out through the intake manifold carrying a mist of oil with it. This oil laden mist is then burned in the combustion chamber. This scenario has been repeated countless times. If ever your engine gets gas into the oil this will occur. In addition to the new carb did the "tech" suggest that you need to install an inline fuel cut off valve and shut the valve off except when you are actually using the machine? Having an inline cut off valve and using it consistently is the ONLY way to ensure you never have this issue again. Even after you change the oil (and filter if equipped) you can expect some smoke for a few minutes until all the residual oil is burned out of the exhaust system.
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Yoou didn't state what tractor you had, but I think if you look in the owners manual, it'll tell you to turn off the engine at higher speed. Thee carb has a fuel shut off solenoid that blocks the Main Jet when the key is turned off. The engine is supposed to keep turning over for a few seconds to "purge" fuel vapors from the HOT exhaust system to prevent after fire. Back fire is through the carb, BTW. What I would do, is put a strong dose of carb cleaner in the fuel and see if that might clean up a varnished Main Jet. A lot of people like Sea Foam. EPA Mandates require that these run on the lean side because of emissions regulations. There's really not much "wiggle room", if the jet gets slightly restricted, because it's aalready on the ragged edge of being too lean. Also- Check carb/intake mounting bolts.gaskets. A vacuum leak would also lean out the fuel mix.
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I don't know where to start first. Exhaust valve seat loosened, usually does not happen unless there is overheating of the head and cylinder, overheat could be caused by debris (even mouse nests) under the cooling duct sheet metal. Any discovery of loose valve seats should entail a thorough search for a cause of overheating. Blue loctite......one of the least durable of retaining compounds. Should only be used where minimum retention of the parts is desired in applications were the fasteners are expected to be removed and reused periodically. Piston rings......If it were not for the fact that you saw smoke PRIOR to your teardown, I would suggest that maybe your rings were not aligned (staggered) properly on the piston, and they may or may not be staggered properly, but I don't think that is your primary cause of the oil blowing smoke. I presume the oil is blowing out in the exhaust plume. Two things spring to mind (based on the data). The engine suffered a major overheat, this may have "egg shaped" the cylinder enough to permit excessive blow by to enter the crankcase. The oval shape of the cylinder, and consequential loss of ring sealing causes oil consumption two ways. (1) Direct migration of lube oil into the combustion chamber on the intake stroke. (2) Indirect migration of lube oil into the intake manifold as the crankcase breather/oil mist separator becomes overwhelmed by a highly pressurized crankcase during the compression and power strokes. (3) Cylinder head and cylinder deck are warped, causing the new head gasket to seal poorly. Another possibility could be the presence of gasoline in the crankcase due to a faulty carb (if gravity fed) or a faulty fuel pump (if pump fed). Did you change the crankcase lube oil after doing the other repairs? If not, the already contaminated lube oil may just be continuing to boil off and burn the gasoline that leaked in there before you tore the engine down. Of the above scenarios, the fuel pump is the least likely cause.
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canadave
14 years ago
I had an oil leak in my Simplicity 18 HP Conquest. Turned out mice got between the engine and cowling over the winter and the engine overheated in the spring and the engine was toast. Someone on this site put me onto a 20 HP B&S Vanguard that was 20 HP and on sale at an excellent price. I love my Conquest but too bad it doesn't have a temperature or a heat alarm which would have saved me a lot of money
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rustyj14
14 years ago
For next winters storage, try stuffing a couple of those smelly clothes dryer sheets in around the engine shrouding. Mice just hate that smell, and will make their winter quarters in something else, not your engines!
I have a customer who stores his tractors, etc., in a shed. The inside of the shed has that pink fibreglas insulation on it, and the mice have taken a great liking to that stuff! They use it for their nest material, and every spring, his machines are stuffed full of it, with the result that the mice have eaten the insulation off the spark plug wires, and built their nests from the pink stuff, and nothing starts! I opened up one of his engines, and there, under the flywheel cover, was Momma Mouse, and 5 new-born babies, all pink and fur-less! And, a bare spark plug wire!
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walt2002
14 years ago
Which is why I put two fresh Decon boxes in my storage shed each fall.

Walt Conner
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jerry_nj
14 years ago
Yes, me too. My 1993 B&S 18 HP L-Head had an engine fire a year back. I stopped and turned the engine off and got ready to run but opened the hood (Craftsman GT6000) and could see it was dried grass burning. The grass was up under the cover for the cylinder heads.. not much cooling. The engine seems undamaged, but I now check to see if the mice are building nests from time to time. Need to do before getting into any serious mowing this spring. I haven't done that yet.
That old B&S engine is bullet proof... I'd guess it has about 1500 hours on it... no visible smoking but does burn a little oil

Hum, did I go off topic, must be my age.
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