Oil pump bypass spring failure?

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I’m in the middle of correcting a low oil pressure situation in my 65 Ranchero. The oil pressure drops upon warmup to a level that triggers the oil pressure switch (light). I think that the bypass valve inside the oil pump has lost its staying strength, moreso when hot.
I pulled the oil pump out and opened it up. No terrible marks inside it, but wear could be a contributing factor.
The truck runs great, but has been slinging some oil out of the dipstick tube. (This may be a pcv valve issue that I am working in parallel)

I’m asking if you all have ran into this in your experience…

New parts will be here by the end of the week and installed, so I will know then if I have found the smoking gun.
 
Are you checking it with a mechanical gauge?
The reason I ask is years ago I had a 1990 Dodge pick up that when I came to a stop the oil pressure dash gauge would drop then come back up and on and on.

I was positive it was the oil pump giving me problems, had alot of miles on it so it sounded logical.
After replacing the pump and having no improvement I replaced the sending unit and that fixed it.

Don't know why I was determined it was the oil pump other than I had never seen a defective sending unit act that way but when I put it back together with no improvement I would have liked to see the look on my face when I thought "why didn't I change the sending unit first?"

The only upside to it the oil pump was surprisingly easy to change even though I had to drop the pan.
 
Are you checking it with a mechanical gauge?
The reason I ask is years ago I had a 1990 Dodge pick up that when I came to a stop the oil pressure dash gauge would drop then come back up and on and on.

I was positive it was the oil pump giving me problems, had alot of miles on it so it sounded logical.
After replacing the pump and having no improvement I replaced the sending unit and that fixed it.

Don't know why I was determined it was the oil pump other than I had never seen a defective sending unit act that way but when I put it back together with no improvement I would have liked to see the look on my face when I thought "why didn't I change the sending unit first?"

The only upside to it the oil pump was surprisingly easy to change even though I had to drop the pan.
Yes, verified with a mechanical gauge. Also , a brand new motorcraft sending unit. Thanks for asking!
 
I got a standard oil pump installed and I now have about 20 psi when the car is hot and idling (was near zero). Yay!

I have to pull the oil pan again, as I must have pinched the rear portion of the gasket during installation.
 
I use alignment studs on just about everything that requires a gasket.
Cut the head off the correct size bolt, cut a slot in it for a screwdriver in case it's needed to remove stud.
Keeps the gasket from moving around.
 
I use alignment studs on just about everything that requires a gasket.
Cut the head off the correct size bolt, cut a slot in it for a screwdriver in case it's needed to remove stud.
Keeps the gasket from moving around.
The FelPro gasket came with plastic studs to snap the gasket and pan to the block, but I didn’t use the pair nearest the flywheel as I couldn’t get the pan on as the center link was in the way.
Bad on me (read: doofus!), for trying to save a little bit of time.

I will drop the center link and do it correctly next week…
 
It's a Ford, the bearings are probably down to the copper. Worn out.
 
It's a Ford, the bearings are probably down to the copper. Worn out.
The only cap that I removed was the one nearest the flywheel and it did show some copper. I showed it to my cousin, who has been working on machinery (anything on a farm, trucks, cars, etc) and he said that was normal for a ford with over 75k miles and that it would be ok (not a daily driver).

Interesting story regarding my cousin is this:

He came across a Chrysler 300 AWD and the engine had a hole in the side of the block. The hole was in the side just above the oil pan.He somehow welded in a plug, slapped it back together and it’s now his wife’s daily driver (and it’s a nice one).
 
Follow up:

After finding a giant oil leak at the rear of the oil pan, I found that I had inadvertently installed the rear main seal backwards.
In removing the one piece oil pan gasket, it broke, so I ordered a replacement oil pan gasket and rear main seal, reassembled everything and now it’s good.

Additionally, I now have 45 PSI of oil pressure at cruise and about 15 PSI at idle, both when the engine is hot (solid 180 degrees).

I will now drive it regularly and make some adjustments (brakes, carb, timing), and I need to adjust the rear axle a bit as the rear tire on the driver’s side rubs just a bit during rear suspension compression (po had air shocks that have been replaced with KYB gas adjust models)…
 
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