VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Oil pressure woes

Since my last post I removed the pan, cleaned the screen and reassembled with good results. I had 10 lb while on the road and a solid 5 lbs at idle with a warm engine. GREAT. But now at any given time while driving on the road the pressure gauge drops like a rock to near 0 so I stop and at idle the pressure slowly comes back to normal. The pump looked fine when it was apart, and when testing with a drill we got 12 -15 lbs to fill the troughs. What now? Could it be the vanes in the pump getting hung up and not moving?

What year?

You don't have your year of car listed in your profile. So, when asking questions please include your year of vehicle.

Sorry, 1931. Now when the pressure drops I shut it down for moment, restart it and the pressure is back for a while. I am thinking the screen is plugged again.

If you find that the screen is not plugged then you should probably replace the oil pump.

Do you by any chance have a felt pad on the rocker arms? When I rebuilt my first 194 and was looking for parts the catalog said, "Don't forget to install a felt pad, helps valve lube and makes for quieter running." (Or words to that effect) So, not knowing any better, I bought and installed the pad. BIG MISTAKE!! The felt pad shed something terrible, plugged the oil screen and totally ruined the bottom side of the engine which had just been re-poured, rods and mains. So, another complete Babbitt job. It behaved just the way you describe in your opening message. IF it is in there, remove it, drain and flush the engine oil a couple of times to get all the felt residue out.

Where might the felt pad be? I have found lint in the oil pick up screen. Can some one tell me which way the vanes are supposed to be installed in the rotor? The vanes have a tappered side, on the spare pump that i checked the tapper is on the back side of the rotation while the oil pump in the engine the tapper was on the front. On a guess i flipped the vanes so the tapper is on the back side and went for a test ride. 15 psi on the road and 5 psi with a warm engine at idle.

The aftermarket felt pad is on top of the rocker arms under the valve cover.

Looking in my 1929 repair manual it showed the vanes/tapper is facing the direction of rotation and looking at the bottom of the pump it rotates counter clockwise.

And another warning re low oil pressure. On the 194, you can show normal oil pressure with almost no actual flow. I have seen it on two engines, mine being one of them. The other we were unable to get oil to the rocker arms. Tried everything except looking at oil pump as we showed normal oil pressure. Finally after studying the repair manual and seeing how the oil circuit flows, it will show full oil pressure if there is any flow at all. In the case of both engines, there was not enough flow to force oil to the rockers, and also the center main ran dry of oil, In the end, both engines lost the center main even though we showed oil pressure. In the case of my friend's car, the oil pump had one spring broken and the other bent, along with approximately .040 play in the shaft and a scored bottom plate. Replaced the pump with a new one, restored oil to the rockers but had to replace the center main and line bore the engine after only 1,500 miles on a re-babbitt job. So, don't just go on oil pressure, if you are getting lint on the screen, drop the pan, clean it carefully then do a complete evaluation of the pump, otherwise you are probably looking at a re-babbitt job. Just my experience.

Just an update. Right or wrong I don't know but I flipped the vanes over and now have a solid 15 lbs till the engine is warmed up and 10 lbs running 5 lbs at idle and steady dribble of the rocker shaft.

Perfect! Your oil pump is doing exactly what it is supposed to do.

Thanks for posting the update as it may help others with a similar problem. Too often a problem is resolved but the "cure" not posted.