OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs & Stratton - ever seen a gasket blow out?

Those of you that have been around mowers long enough to see such a thing...

I was given a Rover mower with a Briggs & Stratton Sprint 375 engine. It was given to them too and they thought it had blown the head gasket, and claimed it was "leaking oil or fuel". They even warned me to bring some cardboard to stop the oil leaking in our car. It did have a little oil on the deck, but that could have just been someone spilling oil during an oil change. A half hour drive home left no oil leaks in the car.

So I pulled the sparkplug and gave the cord a light pull. Spark ok. The crankcase was still full of oil, so I put some fresh fuel in, primed, and gave it a pull... It started and ran great. No smoke, ran smooth... So I degreased it in case it did have an oil leak (knowing I'd see any fresh oil on a clean deck). But nope, still no leak.

Then I pulled the fuel tank off and noticed oil leaking from the crankcase gasket, and about an inch of the gasket was hanging out... Like it had either been blown outwards by force due to some fault, or, was not fitted correctly in the first place when the engine was being bolted together at the factory.

My question is... Is there an engine fault that could cause the crankcase gasket to blow out? I'm concerned if I replace the crankcase gasket, it could blow out again (if that's even possible/likely?).

justallan,

I have had that in the past and it is only about 1" of gasket that gets blown out. It can be causeed by the bolts on the crankcase being loose.

Once you replace the gasket all should be ok.

Bruce, for the case of saving time and not removing the boss is it possible to split the case by say a cm or so and replace the gasket with blue RTV sealant?

Joe it would be quicker to pull it apart because getting the boss off is usually fairly easy and apart from that you have different thickness gaskets for the crankcase.

Great stuff, thanks!

OK cheers Bruce, never really opened a Briggs before, usually if the crankcase needs to be split the engine has let go and I dump it.

Joe,

I would not throw them to the dump these days because all the old motors are better than the new stuff coming out.

Halfway through doing it right now... The bolt where the 1 inch of gasket was blown out was loose! I wouldn't have been able to replace the gasket with sealant though... Even though I left it to drain overnight, there was oil leaking out the join, because inside the sump there's these fin "channels" that were still holding oil.

Maybe if I'd left it upright I might have been able, but the crankshaft oil seal is weeping slightly too. So I may replace that as well while it's apart.

BTW...

When I used to work on VCRs, there were little arrows on the nylon gears that were used to line up the timing correctly. I saw a similar arrow on what I assume is either a cam for the valves, and/or oil pump. I *think* I've managed to keep it in the same position it was when I removed the sump - but - is there a more certain method I should use to set the timing before reassembling?

justallan,

The timing is usually easy with the B&S engines because you only have to line up the dot on the crankshaft with the dot on the cam.

I saw that dot and thought it might be part of it... Wasn't sure though if I had to rotate the crankshaft until the cylinder was all the way in, out, etc., tug on right ear while hopping on one leg and spin around 5 times. So THANKS!