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briggs engine smoking problem


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05-07-09, 03:06 PM   #1  
briggs engine smoking problem

ok, I have a b&s vangaurd 15hp engine 28q777. Ive had a smoning problem. I did a leakdown test and everything seems fine. I put a new headgasket and it ran fine for 3 minutes and started smoking again. Could it be the crankcase breather? I took it out and am soaking it in kerosene. The airfilter is soaked in oil.

 
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05-07-09, 05:21 PM   #2  
It could be the crankcase breather or the new headgasket may be leaking.

The oil in the air filter points to the headgasket a high percent of the time.

 
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05-07-09, 08:08 PM   #3  
Ok, so this dam thing is really stumpmig me and I gotta get my grass cut! I put the new gasket on and torqued it to 20 ft lbs of torque since it calls for 220" lbs. Also took the crankcase breather out and swished some kerosene and blew it out. It runs great for 5 minutes and then boom it smokes like crazy white smoke. WHAT CAN IT BE!!!??!!

 
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05-07-09, 09:00 PM   #4  
Is there gas in the oil (smell it)? Did you torque the head bolts in the correct pattern?


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05-07-09, 09:09 PM   #5  
The oil smells fine. I basically snugged all the bolts then torqued the top middle one to 20 ft lbs then the bottom middle, then the sides then the rest. Is this not correct? im pretty sure that the new headgasket is blown.

 
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05-07-09, 09:22 PM   #6  
You're probably right. I suggest checking the head surface with a straightedge. Make sure it isn't warped.


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05-07-09, 09:35 PM   #7  
OFF IT GOES AGAIN!!! Anything else would cause me to blow gaskets? Is it ok to use the new one?

 
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05-07-09, 09:56 PM   #8  
Improper torque, bolt sequence, and/or warped head or distorted surfaces is all that would be likely to cause blown head gaskets. Check the head and block, make sure surfases are cleaned of the old gasket, no oil, no sealants, and look up the bolt tightening sequence.


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05-08-09, 06:46 AM   #9  
Any idea where I can find it?

 
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05-08-09, 01:34 PM   #10  
Update: put another headgasket on the right way this time. Ran great for about 15 minutes then started smoking again. I took the breather out again and cleaned it with carb cleaner. The whole inside of the airbox is oily and I noticed oil in the intake after the carb. I really dont think its a headgasket as it will only smoke now if you put a load on it. Should I buy a new crankcase breather?Why is it getting so much oil in there?

 
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05-08-09, 01:51 PM   #11  
The problem stems from too much crankcase pressure. The most common source of that is a blown head gasket. The pressure in the crankcase simply blows the oil through the crankcase breather tube into the intake (air filter).

When that pressure is normal (the amount generated from the blowby at the ring gap of the piston rings) the oil stays in the crankcase. If the breather is faulty you can have a similar problem, or if the oil level is too high (either from an overfill of oil or gas intrusion from the carburetor).

The most common cause is the blown headgasket, however excessive blowby from the piston rings can cause it. The latter, however carries a number of other problems with it which would indicate something is wrong with the overall condition of the engine. A crack in the head (although unusual) might cause excessive pressure if the crack is severe and located in a manner to direct head pressure into the crankcase. An OHV engine might have something like that.

From experience (unless you are cursed) - if you have worked on the same thing twice and it still doesn't work, it's something else.

 
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05-08-09, 03:53 PM   #12  
Yea Im pretty sure its the crankcase breather. I took the tube out and ran it for 1/2 hour and it was much better. Ive replaced the head gasket twice so I hope to god that aint it. I dont understand why oil would be spewing out of the breather though? Thought only gasses were supposed to go through it.

 
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05-08-09, 05:10 PM   #13  
When an engine is running the crankcase is literally a fog of oil droplets. With the normal amount of crankcase pressure those droplets are filtered at the base of the breather tube and drain back into the sump of the engine. But, when you have excessive pressure, those droplets are forced past the shield and up the breather tube.

Normally when something is wrong in an engine that causes what you're seeing, it will show up in either a load situation or higher rpms. Either of those is when the governor opens and allows the maximum amount of air into the combustion chamber = maximum blowby or compression transfer to crankcase through the blown headgasket. However, it can show up earlier depending what is feeding the pressure in the crankcase.

 
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05-08-09, 05:40 PM   #14  
Yea I noticed last time when I was mowing that it wasnt smoking at all until I either engaged the blades or when the motor was under a load. So WHAT IS MY PROBLEM!!!

 
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05-08-09, 06:26 PM   #15  
Is it possible you are running the engine at too high of RPM, which would force oil into the breather. It should be running 3400-3600 max. Have a good one, Geo

 
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05-08-09, 08:17 PM   #16  
I am just wondering what did you use to clean the head gasket surfaces?? Did you use a scraper or one of the "scotchlock" type "wizz wheels?? If you used the "scotchlock" wheel on a drill or diegrinder ( & I know everyone tells me they never have any problem with them & have used them for years without trouble)) you have probably removed enough material from the block &/or head that the head gaskets won't seal 'cus the surface isn't flat anymore... I've replaced a Big Cam 855 Cummins engine (& others) because the head gaskets would always leak & I found out the origional repair was cleaned with these ""Scotchlock"" discs.. & many other parts. Recheck the block & head to be flat & look very close for gouges & score marks.... Roger

 
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05-08-09, 09:00 PM   #17  
I did use a die grinder. Theres no score marks and I put a straight edge one the head and it wasnt perfect but really wasnt that bad.

 
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05-08-09, 09:38 PM   #18  
The thin area between the cylinder and the pushrod chamber is where the head gasket leak causes problems. This area is also thin, and aluminum. The thin aluminum can disappear really fast under a die grinder. Check the block, paying special attention to this spot. Aluminum will sand away almost like wood. If you can see that it and the head are not flat, then it's distorted. Sounds to me like what has happened.


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05-09-09, 06:43 AM   #19  
Die grinder - ouch!!! Need to revisit the head gasket issue a third time.

 
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05-09-09, 06:45 AM   #20  
Sounds like I need a new motor!

 
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05-09-09, 07:01 AM   #21  
Not necessarily. The head can be resurfaced fairly easily by a machine shop. The block would be more difficult. Maybe the head is all that's messed up.

 
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