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Briggs and Stratton 7 hp 170403
- Thread starter wizard67
- Start date
bertsmobile1
Lawn Royalty
Run the mower for 5 minutes, shut it off & thn open the dip stickafter the engine stops revolving.
If smoke comes out then you have an internal head gasket failure.
Oil coming out of the breather is a symptom of a problem, it is never the breather itself.
If smoke comes out then you have an internal head gasket failure.
Oil coming out of the breather is a symptom of a problem, it is never the breather itself.
Run the mower for 5 minutes, shut it off & thn open the dip stickafter the engine stops revolving.
If smoke comes out then you have an internal head gasket failure.
Oil coming out of the breather is a symptom of a problem, it is never the breather itself.
Tks Bertsmobile1.
I will do the test.
Check your oil level, if it is high check to see if it smells like gas, you have a problem with your carb. The float needle is not seating properly and fuel is running through the carb into the crankcase.
No Gas in the oil. Tks for the info.
Run the mower for 5 minutes, shut it off & thn open the dip stickafter the engine stops revolving.
If smoke comes out then you have an internal head gasket failure.
Oil coming out of the breather is a symptom of a problem, it is never the breather itself.
The test revealed smoke in the Dip Stick. I removed the head found excessive oil on top of piston and valves. Gasket seems ok will replace. Hope it's not the rings.
(Account Closed)
Well-Known Member
Sounds like compression rings leaking compression into the crankcase and the oil rings not keeping oil below the wiper ring
A "Leak down test" would confirm this...
*Bert, how would a bad head gasket cause higher pressure in the crankcase forcing oil out the breather? Leakage would just be into the atmosphere, no? Or are you thinking of an OHV engine with compression going down where the push rods would be?
I assume it's a flat head engine..
A "Leak down test" would confirm this...
*Bert, how would a bad head gasket cause higher pressure in the crankcase forcing oil out the breather? Leakage would just be into the atmosphere, no? Or are you thinking of an OHV engine with compression going down where the push rods would be?
I assume it's a flat head engine..
Last edited:
Sounds like compression rings leaking compression into the crankcase and the oil rings not keeping oil below the wiper ring
A "Leak down test" would confirm this...
*Bert, how would a bad head gasket cause higher pressure in the crankcase forcing oil out the breather? Leakage would just be into the atmosphere, no?
I assume it's a flat head engine..
Unfortunately that is what it seems to be. Will leak down test to confirm.
Tks SRTsFZ6
Hi,
I have a 1967 Briggs and Stratton 7 HP 170403 that is leaking oil from the breather. I replaced the breather, but am still having the issue. The engine only smokes when the breather starts leaking oil. Any help would be greatly appreciated.
Thanks
Alex
Update, did a Leak down test hot and cold came back normal. Replaced Head Gasket, no kink in hose, but still having the same issue. Wondering if the new Breather is defective.
Removed breather hose from carb and added a section of clear tubing and the oil starts leaking after 30 sec running.
bertsmobile1
Lawn Royalty
Oil comes out of the breather for only 2 reasons
1) the oil level is too high so there is oil in the crank case fume
2) there is excessive pressure in the crank case.
The latter can be caused by
1) head gasket broken between the cylinder & pushrod tunnel
2) worn rings
3) cracked head
4) cracked piston
5) cracked barrel
The breather is just a one way valve.
Some do have a small drain hole in them to allow excessive oil to drain back into the engine on the exhaust / compression strokes.
Very rarely a worn crank shaft seal can cause the crank case to pressureize but that only happens at operating speeds.
Excessive carbon build up on the piston can by
a worn inlet valve guide
Excessive crank case pressure
Worn scraper ring
Worn bore
leaking head gasket.
1) the oil level is too high so there is oil in the crank case fume
2) there is excessive pressure in the crank case.
The latter can be caused by
1) head gasket broken between the cylinder & pushrod tunnel
2) worn rings
3) cracked head
4) cracked piston
5) cracked barrel
The breather is just a one way valve.
Some do have a small drain hole in them to allow excessive oil to drain back into the engine on the exhaust / compression strokes.
Very rarely a worn crank shaft seal can cause the crank case to pressureize but that only happens at operating speeds.
Excessive carbon build up on the piston can by
a worn inlet valve guide
Excessive crank case pressure
Worn scraper ring
Worn bore
leaking head gasket.