Pressure in oil tank?

[seadoobie]

Ok so I've been having a problem with my one way check valve leaking oil into my engine compartment. I thought the valve may be faulty & replaced it with new valves twice now and it still continues to leak.

I found that when the oil cap is tight it does this, oil creeps up the vent tube and drips out. I have to keep the cap kinda loose and then things are fine, no leaks from the valve. It seems like pressure is building up in the oil tank or something to push the oil out like that.

I'm not sure if these oil caps vent pressure or not, since valve is supposed to let air in to stop vaccum lock, but I dont like loosing oil and also having to clean it up all the time.

Anyone else have this dumb problem? Thx in advance!

 

[CaptSteve]

There should be no pressure in the tank, only suction. There is nothing that pumps into the tank.

This may be a silly question, but are you sure you have the check valve pointing the right way. The check valve is suppose to let air into the tank as the oil is sucked out, but stop oil from going out the tube. If you have the valve backwards, no air can enter the tank and suction will build up. Eventually, you could even implode the tank from the suction. The arrow should point toward the tank.

Also check that the hose is not block and that the end of the hose is higher than the tank. Loosening the cap is doing what the check valve should do. Letting air into the tank.

This is a common problem, ask me how I know.

 

[seadoobie]

Yeah the arrow is pointing toward the tank =)....I checked that several times....even tested it with another piece of hose to make sure after I put the valve on. This is why I dont understand this problem, it's like reverse vacuum lock or something. I did buy the replacement valves from a local napa store, but I dont think that would be a problem, their just simple one way check valves.

I cant remember if the oil cap has a gasket/o-ring on it or not atm. If not it could be creating to great of a seal for the valve to compensate for...creating back pressure/expansion somehow. Only thing I can think of atm since I'm having to loosen the cap to do the valves job. I'm changing out the oil filters next time weather permits, I can get a better look at things then & report back, has to be something simple though. And I am going to check the valve again to be sure.=)

 

[CaptSteve]

The valve may be your problem. If the check valve is from a cars vacuum system, it may be spring loaded. Some of those valves will only open at a certain pressure and that pressure may be too great. You need a liquid type check valve. One that is always open until a liquid flows back into it. These have a float inside that floats up to block the hose. You should see if you can get an oem valve or one that is made for liquid.