How would a hung open oil pressure relief valve manifest itself? (technical)

[phartman]

21-stud '36LB. Excellent condition up until this past weekend. No funny noises, motor pulls strong. Less than 5,000 miles on a rebuild. 20-50wt oil. I had been driving on I-64 for about an hour. There is an idiot light wired + a pressure gauge. Idiot light comes on, indicating pressure has dropped to the 8-10# range. No other changes.

Checked the pressure at speed. No more than 10-12 lbs at best. Changed the sending unit to the idiot light. Same results. Changed the oil. Same results.

The motor is converted to an electronic fuel pump with the mechanical pump rod removed. Some have suggested I put the rod back in the oil fillup tube, blocking the hole to the oil pan. I did, no change to the oil pressure.

I am beginning to suspect that the relief valve is hung open. Good pressure when the motor is cold, but drops as the engine progressively warms up. Motor otherwise runs well. 160 degree water thermostat, doesn't overhead, pulls strong.

Thoughts? Ideas? What would a hung open relief valve act like?

Thanks for your help here.

[alan]

need a little more info. what was oil pressure before problem? could be a couple of problems--I will list what I have found to other engines that have done the same thing--cracked pick-up tube on oil pump, broken spring in releif valve on oil pump ( if equiped with later pump), fuel push rod bushing worn, stuck or sticking relief valve, also had one with some sort of gasket materiel sitting between plunger and seat and last but not least a bad bearing-not really bad but had too much clearence-this is one a 59A in a 36 wagon-owner just added hd lucas oil stabilizer to engine a picked up about 10 lbs

[Willit Stop]

I had a similar problem with mine.To make a long story short,someone assembled the oil pump wrong.Purely by accident,I parked the car uphill in the driveway and the pressure would stay at 30-40 all day long at idle.As soon as I drove it onto the street and the RPM's rose,the pressure would drop to 5.I removed the pan and pump a couple of times and finally found the problem. The pickup tube is soldered to a tin cup that encloses the impellers.Inside the cup between the cup bottom and the impellers was a steel disc that was supposed to be(?) on the outside bottom. Anyway,the disc acted as a spacer and left a gap between the top of the cup and pump.Above idle there was more demand for oil and the pump would draw more air than oil.To fix it I used a big fat O-ring where the top of the cup meets the pump.It worked.
My advice would be to park uphill on a steep incline and check the pressure through a range of RPM's. Then do the same parked downhill.For your sake,I hope this isn't the problem because to remove and replace the pan is an all day task.I hope this helps.

[phartman]

"Before" I was getting 3-5# at idle, and 20 lbs or more at operating speeds. Hot weather, cold weather, thin oil, thick oil- didn't matter. The problem started to happen after a Saturday morning cruise over a couple of particularly bad, jarring roads with potholes. Got through them, and the oil idiot light came on (indicating oil pressure had dropped below 10#) then went out. The next day was when I was out on the interstate. No problem for the first hour. Stopped to see a friend and the truck sat for maybe 90 minutes. Went back out on the interstate, and the idiot light began to "glow", pressure gauge is a notch under 10#.

Could something in the oil pickup or pump assembly jarred lose over the rough roads? My guess is that it has something to do with those potholes. Prior to that, pressure was good.

[trainguy]

I had the same problem with my 46,Thinking it was the relief valve stuck.before taking the intake manifold off to check the relief valve,I put a bottel of Marvel MO.Within 5 miles it had free'd up the valve and have had no problems since.I don't know what is in MMO[it's a mystery]but the stuff works,and smells good to.

[trainguy]

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Sorry I failed to answer your question.Your symptoms mirror the problem I had.I concluded that it was a stuck relief valve.Phil

[phartman]

Phil, I am suspecting that is exactly what the problem is. I just went out today and bought all the gaskets and parts to tear down the intake. But before I do that, I think I'll give it the Marvel Myster oil treatment. How much did you use??? Yes it does smell good. Straight? On the rocks? Chaser?

https://www.youtube.com/watch?v=HwfA59_6RFM

[trainguy]

One bottle about a quart,I was amazed how fast it freed the valve.I had a intermitent sticking valve in my 1912 Case,put MMO in the gas after about a hour running problem solved.Its a mirricle,and smells good to.Phil

[G.M.]

I don't think bumps have anything to do with the bypass valve. The pick up tube could have cracked where it is welded to the boss that bolts to the pump. Drain the oil and put your finger up in the drain hole and see if the whole pick up assembly moves. I don't believed if you mentioned what type of oil pump, old type or latter one with a bypass valve. G.M.

[Jack E/NJ]

Doesn't taste too bad either. Whenever a motor hasn't been run in few months or longer, I always suck some MMO up into a small hose and try to fill it without getting too much in my mouth. Then hold the end shut with my tongue or lips while I insert the other end in each sparkplug hole and blow. Let it set awhile. Then crank the engine without the ignition on to distribute it around the cylinder walls and rings. Probably better ways to do it than siphoning MMO into your mouth ---- but it's quick and easy and, as I said, it doesn't taste bad at all. I may swallow a bit in the process --- but I don't inhale. 8^)

Jack E/NJ

[phartman]

Originally Posted by G.M.

I don't think bumps have anything to do with the bypass valve. The pick up tube could have cracked where it is welded to the boss that bolts to the pump. Drain the oil and put your finger up in the drain hole and see if the whole pick up assembly moves. I don't believed if you mentioned what type of oil pump, old type or latter one with a bypass valve. G.M.

No really sure. It is a '36 LB block. Which one would that have???

I just assumed it had the bypass valve in it.

[phartman]

Well, I tried the MMO cure, and it runs marginally better, but not back the way it should. However, I must say the truck smells better after a spin up the road with the MMO fumes oozing from the breather. My son called it "minty fresh" rather than the previous "old man's old truck funky."

I guess we are making some progress here.

[J Franklin]

Originally Posted by Jack E/NJ

Doesn't taste too bad either. Whenever a motor hasn't been run in few months or longer, I always suck some MMO up into a small hose and try to fill it without getting too much in my mouth. Then hold the end shut with my tongue or lips while I insert the other end in each sparkplug hole and blow. Let it set awhile. Then crank the engine without the ignition on to distribute it around the cylinder walls and rings. Probably better ways to do it than siphoning MMO into your mouth ---- but it's quick and easy and, as I said, it doesn't taste bad at all. I may swallow a bit in the process --- but I don't inhale. 8^)

Jack E/NJ

Jack go by a large syringe. They work great for jobs like you describe and might save a doctors visit. they are great for filling shocks also.

[trainguy]

Originally Posted by phartman

Well, I tried the MMO cure, and it runs marginally better, but not back the way it should. However, I must say the truck smells better after a spin up the road with the MMO fumes oozing from the breather. My son called it "minty fresh" rather than the previous "old man's old truck funky."

I guess we are making some progress here.

Give it a little time.Phil

[my4dv8]

We had a motor with 2000 miles on rebuild , while the symptoms were not the same as you describe the culprit was the relief valve . The cause was found to be some faulty machining on the front cam adapter to go from an early cam to an 8ba style to run an 8ba distributor, it was found despite having the correct 8 ba cam gears the adapter was rubbing on the front cover. Oil pressure when cold was ok but at speed when warm would fluctuate and at idle when hot would fall to less than 5lb.
What we found was lots of very fine metal filings throughout the motor, these stood on end on a magnet like hairs. There was a collection in and around the relief valve also causing it to hang slightly open.

[phartman]

Looking at the relief valve design, it looks like it wouldn't take much to wedge it partially open. Don't know, but suspect that might be the culprit.

[trainguy]

I had a small chunk of silicone gasket goo dislodge a get caught between the ball and seat in a 22 rickenbacker and drop the low rpm oil pressure,I am now carefull with the use of "Blue Goo".Phil

[phartman]

Originally Posted by trainguy

I had a small chunk of silicone gasket goo dislodge a get caught between the ball and seat in a 22 rickenbacker and drop the low rpm oil pressure,I am now carefull with the use of "Blue Goo".Phil

Hmmm, gasket seal figured into part of the puzzle, but not all of it. Finished up my winter project, and finally found out what was going on with my motor.

I took the truck to the excellent folks at Joe Smith Early V8 and Hot Rod here in Richmond. They pulled the pan and, low and behold, the motor was rebuilt way way back when with an unconventional oil pump. Doug Walker, the owner at Joe Smith, speculated it might have been a pump off an industrial application, or some type of aftermarket rig. In any case, when the rebuilder when to install the pump, he was missing the proper gasket at the base. He used silicon to cobble together a makeshift seal.

Over the years the pump worked its way loose, and the silicon bead began to deteriorate. After time, there were gaps in the seal, and it began to suck air. For a while, overfilling the pan with too much oil filled the gaps, and gave the motor adequate pressure. Then this past summer, the seal let go, and there went the oil pressure.

Doug and the fellas installed a proper Henry Ford pump, and the ol' 21-stud is running like a champ again with 30lbs of oil pressure.

I am a happy camper. Good to see the lil' motor running like a sewing machine again.

[Binx]

Good to hear phartman!! You were wise to have backup instruments and heed their warning. Makes me wonder if Melling was making crappy long pumps at that time of your rebuild and wobbled loose. I'll bet Walt might know.

Lonnie

[Ol' Ron]

It might be the gear on the end of the cam, the earky ones were just pressed on and 20/50 oil might have loosened it. The later cams had a flat to prevent this. That 20/50 stuff is bas s***.

[Jack E/NJ]

Good to know, Ol' Ron. I guess that's why Ford now recommends their 5/20 synblend. My 21-studder seems happy with it. 8^)

Jack E/NJ

[Bassman/NZ]

Woah! 20-50 is bad? What gives?

[Ol' Ron]

When these engines were designed, they recommend 30 in the summer and 10 in the winter. The onlu teason to run 20/50 is to make the oil pressure gauge happy. It rund hotter and takes more power to run the pump and that my friend is hard on the oil pump drive gear on the old cams. How do I know this?? I spun one.

[G.M.]

Originally Posted by phartman

No really sure. It is a '36 LB block. Which one would that have???

I just assumed it had the bypass valve in it.

If a latter oil pump with the bypass is installed that could be leaking. I have seen several that needed a large spacer on the spring. Look in back posts, I have describe several times how to test and adjust the pumps. G.M.

[Lawrie]

Ron, its an easy job to mill a small flat on the cam to fit on the gear with the flat ,,Well if the engine is in bits its easy. Thats what I did.
Lawrie