Head Gasket - Oil Burning Question

optsyeagleOctober 29, 2013

I was reading a question on another site that I am not registered for and it brought up a question I have and I thought I would ask the experts here.


This guy is noticing that his 18Hp Intek is burning oil at around a cup every 3 hours. He shows a picture of his spark plug all gunked up. He has decided to change his head gasket in hopes of resolving the oil burning issue.

On my motor, 16.5Hp OHV Briggs, it burns oil as well. Maybe a little less then a cup every 3 hours but not by much. My spark plugs look like his at the end of the season.

My question is, why would a bad head gasket cause a motor to burn oil?

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It can.
Blow by can build up excessive crankcase pressure.

Easiest test is to- Remove valve cover (have rag handy)
Start engine and look for a "mist" pumping out on the push rod side of the gasket.

    Bookmark   October 29, 2013 at 2:42PM
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Yes, the head gasket leaks a lot of its compression into the crankcase (via the pushrod gallery) and the extra "blow by" then vents out through the crankcase vent into the air filter housing.
The excessive flow out of the crankcase carries a significant volume of lube oil with it and this oil rich mist is fed directly into the intake manifold and right into the combustion chamber (again).
That is the process by which a blown head gasket depletes crankcase oil.
Some folks think that lube oil is "sucked in" through the blown head gasket, but that ain't how it happens.
Do what Bill suggests and if it is leaking you will see it. Probably will need to do this in dim light while shining a good flash light into the pushrod gallery.

    Bookmark   October 30, 2013 at 12:55AM
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Thanks guys. I will take a look at it. I guess that part of the gasket is not holding in much of the compression since I would have figured that one would see some major running issues if any part of the head gasket deteriorated.

I did adjust valves earlier this season and the valve cover has a little oil in it but I wouldn't say if was more then a couple of teaspoons. Certainly not the quart of oil that the motor ate throughout all of last year, although from Mownie's post it sounds like that oil gets redirected around until it's trip ends in the combustion chamber.

    Bookmark   October 30, 2013 at 10:51AM
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My next question is, would there be any longer term problems with this gasket defect (assuming I have one)other then using an extra quart of oil per summer and replacing a spark plug.

Earlier in the season I diagnosed that my carb inlet needle was leaking. I went with the bandaid fix of installing a manual fuel shut off. It fixed the slow starting problem perfectly and the motor runs great during operation. Since I had been starting it in a flooded condition I figured all the gunk was from the rich starting although I was surprised that it would gunk up a spark plug that much. That is why I am now enquiring about the gasket.

I do spray seafoam through the carb and spray a little into the spark plug holes, at the end of each season, since I saw my first gunked up spark plug. I figured if that gunk was on the plug, it is probably everywhere else in the motor as well. Not sure if it helps, but it hasn't seemed to hurt either.

    Bookmark   October 30, 2013 at 11:01AM
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Well, there is no band-aid fix for a leaking head gasket, and while they start out appearing to be a nuisance (the oil smoke), it is much more insidious than that.
The true picture of what is actually happening with ANY uncontrolled or improper loss of compression/combustion from the combustion chamber is more akin to a "blow torch" flame issuing through the breach than just a little puff of air.
The searing hot combustion gasses that are passing through the gap are removing metal from the head AND the block as they consume the remnants of the head gasket itself.
USUALLY.......the engine will become unusable BEFORE the head and block become "trashed" by the flame etching, but it is not advisable to continue running an engine that has ANY amount of head gasket leak. Refer to the old adage "A stitch in time, saves nine". It means that if you sew up (repair) the garment when it needs only a single "stitch", you won't be sewing up an entire seam later (nine stiches).
That ought to paint a clear picture of why the head gasket (if leaking) needs to be fixed "rightaway".
And if that ain't enough to worry about......all that excess oil going back into the combustion chamber will pack carbon into the piston rings and make them less proficient at what they do.

    Bookmark   October 30, 2013 at 11:35AM
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You mentioned the float needle leaking. Is the oil appearing thin and smells like gas. That could be your problem too.

    Bookmark   October 31, 2013 at 12:08AM
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Aww geez! Did i miss that detail about gas in the oil?
Heck yes.....if you have not changed the gas contaminated oil yet....that could be all that is wrong here.
Gas in the oil forces a lot of oil out of the crankcase through the crankcase vent in a fashion much like a blown head gasket, but it is due to the gas coming to a boil when the engine heats up.

    Bookmark   October 31, 2013 at 12:59AM
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Yeah, I was hoping my inlet needle was the cause of the missing oil but I installed the shut off valve, changed the oil in the machine and unfortuneately it is still eating oil. Perhaps a little less then before the fuel leak fix but still more then the 1 oz per hour Briggs considers normal.

My main concern is the look of my spark plug after a season of mowing. It just isn't normal. I couldn't care less about replacing a spark plug but I don't want all that gunk forming inside the engine.

I will look at the head gasket inside the valve cover and if appears to leak I will look at changing it. I appreciate all your insight and advice. Thanks again.

    Bookmark   October 31, 2013 at 9:21AM
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Don't want to be the grinch, but if you've been running that engine for a substantial period of time with that raw fuel leaking into the crankcase oil, you may already have some serious engine damage. Crankcase oil diluted by fuel loses it's lubricating properties - bad things happen.
Best use that manual fuel shutoff valve religiously and get that carb inlet valve fixed ASAP.

    Bookmark   October 31, 2013 at 10:31AM
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Thanks a lot guys for all the info. I found a youtube video on replacing a B&S Intek OHV head gasket for anyone following this thread. Looks fairly easy. The video was well done.


I haven't checked for a mist or leak in my gasket yet. The gasket is only about $8 so I might just change it anyways. It will be a spring job since my tractor is at my cottage and my cottage is all closed up. We Canadians need to be duly punished for drinking too much and chasing after loose women, with a good 4 months of bone chilling winter. Hey, I like to think there are reasons for everything in life and that is as good of reason as any.

On the head gasket, would you guys add a light coating of gasket sealer to it or put it on dry. Also, would it make any sense or difference to turn each push rod around, while ensuring that the exhaust rod stays with the exhaust valve and the intake rod stays with the intake valve?

    Bookmark   November 2, 2013 at 12:35PM
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"We Canadians need to be duly punished for drinking too much and chasing after loose women, with a good 4 months of bone chilling winter. Hey, I like to think there are reasons for everything in life and that is as good of reason as any." That is golden! Made me chuckle. Were you that guy on the loose woman forum looking for valve lash advice? ;) No sealer on the gasket. Clean surfaces a must. Either direction on the push rods. Flipp'em if they want a change of scenery. If you note actual wear from the guide plate- best look closer.

    Bookmark   November 2, 2013 at 10:05PM
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