oil cap flying off

[nevadafreedomfighter]

anyone have their oil cap fly off and hit the hood with a lond bang followed by plumes of smoke? is this normal operation? what causes this? how do you prevent? the engine still runs and engine temp was never over 190. oil was full and needed only about 4 quarts of coolant. thanks for any help.

 

[steelandcanvas]

Is your "slobber hose" plugged up? (crankcase vent) It could be building pressure and popping the fill cap off.

 

[Carl_in_NH]

anyone have their oil cap fly off and hit the hood with a lond bang followed by plumes of smoke? is this normal operation?

Eh, no - it's not normal for parts to depart all by themselves. If the cap just popped off, that would be one thing - but to hit the hood and make a loud 'bang' requires some serious pressure to build up.

It's either as S&C suggests with the breather plugged, or possibly a blown head gasket causing pressure to build in the crankcase faster than it can dissapate through a restricted vent - but I suspect you'd know something was wrong by how poorly it was running or the strange noises it was making.

Pressure like that should never build up in the crankcase.

How's your oil look? Any coolant in it? How about the coolant? Any oil in there?

 

[nevadafreedomfighter]

it was running fine and sounded fine, to me anyway. i will check the solutions listed above. thanks for the help.

 

[Blood_of_Tyrants]

Sounds like a blown head gasket. Have the cylinders checked to see if they are holding pressure.

 

[nevadafreedomfighter]

but isent normal oil pressure higher then coolant pressure? so if it was a blown gasket would coolant have the pressure to blow off the oil cap? it smelled like oil not buring oil, more like exhaust and no coolant smell either. could this be caused by overheating and a clogged coolant system?

 

[gimpyrobb]

Could be valves need adjusting too. I don't know how much pressure there should be, but to shoot the oil fill cap out, that sounds like something is wrong.

 

[Ord22]

a blown headgasket won't make a cap come off, never heard of that. check your breather tube. check to see if your cap was on tight, a big maybe?? if you had a blown headgasket, you will have compression in the coolant system and loosing coolant. check your coolant and oil levels.

 

[nevadafreedomfighter]

the cap was on tight that when it came off it hit the hood so hard it sounded like i blew a rod. i will post picks of the dents on the cap from the hood and the oil splat on the hood. like i said engine still runs fine and starts right up.

 

[woodywood]

sounds like you may have burned a hole in a piston

 

[ODdave]

Very rare but i have seen crankcase fumes ignite and blow breathers and caps off, Gas engines with insane amounts of wash down.

 

[nevadafreedomfighter]

awsome

 

[fstfrdy]

maybe a dumb question but what motor are we talking about. if its the cummins i have seen this on my fathers road truck(400 big cam) the cap would simply come off cause the rubber that you squish to seal it in the cover would become soft from wear and soaked with oil and the extra pressure from high rpms would pop it out.

 

[rosco]

I have seen gasser's ignite fumes in the crankcase, usually, when you are trying to start them, but other times as well. The engine was tired and there was oil dilution w/gas, due to blow by. They blew the valve cover gasket out from under the valve cover.

Are you getting fuel in the crank case? That "pre-heater, cold starting valve", leaking some? We're you lugging the engine, at the time it blew? You should not have smoke in the crankcase, not much anyway. That suggests to me, some internal combustion.

 

[gimpyrobb]

maybe a dumb question but what motor are we talking about. if its the cummins i have seen this on my fathers road truck(400 big cam) the cap would simply come off cause the rubber that you squish to seal it in the cover would become soft from wear and soaked with oil and the extra pressure from high rpms would pop it out.

Probably not a cummins, this is the deuce forum.