1948 pilothouse oil pressure relief valve failure?

[gmk]

Just recently got our "new" 1948 Pilothouse going and found we are rapidly spewing oil out of a failing seal at the top of the oil filter (replaceable cartridge type). Of course a new seal under the screw on handle is obvious.

 

But both the rate/pressure which the oil cam out, and the fact that once I took the lid off of the canister the oil  took a considerable amount of time to drain down from the very top to the level of.the holes in the center tube caused me to question the way the pressure relief valve works.

 

Does the slow draining back down (with engine off and the top of the canister off) indicate the failure of the pressure relief valve? Also does the pressure release valve keep oil from ENTERING the filter when pressure is insufficient or prevent it from EXITING the filter when the pressure is insufficient? 

 

I guess I just don't quite get the layout.  Figure I should be able to test the valve with air pressure but don't know the right place to apply pressure. Also it would also be very helpful if someone could let me know where I might find a diagram on line that clearly shows the circuit the oil follows. It seems as if this pressure relief valve must be threaded into the block form the inside accessible only with the oil pan off? Any help would be appreciated.

 

Thanks,

Grant

[MBF]

Not sure that this is your problem, but you may want to pull the pressure relief valve and see if it is stuck closed.  I'd also remove the lines to the filter and blow them out with compressed air to make sure you have good flow.  I've had new gaskets leak on the cannister, and keep my old ones in case I get another leaker.

[Merle Coggins]

You're on the right track... The oil returning out of the filter goes through the pressure relief valve and if the pressure drops enough for the valve to close it will block off the filter return to ensure oil to the engine first.

Right below where the oil filter return line connects to the block is a plug. Remove that plug to gain access to the relief valve. No need to drop the pan.

[Bobacuda]

I had the oil pressure relief valve stick on an engine I was beating life out of.  Oil pressure in the gage went off the scale, the curled hollow metal that moves the needle was essentially straightened out and expanded...just before a seam on it split and it spewed oil everywhere behind the dash.  I learned to always make certain that relief valve was not stuck before I fired up an engine for the first time after that.

[Fernando Mendes]

[_shel_ny]

The valve.

 

The flow.

[gmk]

Hey Thanks Guys! Things are so much easier to understand with pictures for me. I do have two filters made by different manufactures and I am still unclear about where the check valve that may be in it is located. But this certainly helps the original concern. Thanks!

[Dodgeb4ya]

There are no check valves in the oil filters for the old Mopars.

By-Pass valves... yes on the full flow type filter used on the 25" long block engines.

[_shel_ny]

You are looking for a square head nut (circled in 1st pic) located near the area that the oil filter canister pressure and return lines are.  Spring and relief valve are behind the nut.

 

Nut just out of view in 2nd pic.  

 

Just forward of the starter. yellow arrow second pic

 

Down, and to the right of the distributor.

 

Directly below the oil canister return line fitting location.  Green arrow in pic

[_shel_ny]

Valve may be stuck after removing the nut and spring.

 

 

The relief valve plunger may come out by getting your ginger in the end to work it around and slide out. (pic 1)

 

Valve has a small hole in the center. (pic 2) EDIT:  2nd pic is turned 90 degrees. Oil pan would mount left

 

Hole with valve removed.  (pic)   EDIT:   3rd pic is upside down. Oil pan mounts at upper side of pic

 

 

With the engine off there is no pressure on the valve, so the spring keeps it in the closed position, so

oil will flow from canister when valve is removed. May go on floor/ground depending upon rate of flow.

Edited February 17, 2016 by shel_ny