No oil pressure Ford 5000

[Dave In Chattaroy]

I need some input from you guys. I had posted a while back about the oil pressure light on my ’72 Ford 5000 (diesel w/SOS) coming on and staying on.
I have owned this tractor for about 6 years and use it primarily for stacking and feeding round bales with the Ford high lift loader that’s on it,
so I need to minimize my downtime.
From what I’ve been able to gather possible causes could be, faulty pump, faulty relief valve, broken/worn pump shaft, or bearings out tolerance.
I replaced the oil pressure switch and verified the wiring and operation. I also replaced it w/an analog guage that confirmed no oil pressure.
Some of you suggested that I pull the soft plug and ensure that the oil pump gear was engaging …..it is. Next I pulled the oil pan and replaced the oil pump with a new one, I also cleaned and inspected the sump for shavings and didn’t really find anything alarming. I was told that damaged main bearings would be pretty obvious with residue in the pan. With the oil filter removed oil does get pumped out of the oil supply. Next I pulled the valve cove to see if any oil at all was making it to the top of the motor..….started the tractor, pretty much nothing up top.
So here’s where I’m at today, I suspect possibly the camshaft bearings are done or I have a plugged oil gallery somewhere. I’m about ready to pull the motor and either have it rebuilt or buy a remanufactured long block.
Before I do this am I missing anything???? Any last troubleshooting????
As always I appreciate your suggestions and advice.

Dave
 

[Ultradog MN]

In addition to cavitation problems in the cylinder walls those engines will also cavitate into the main oil line.
Any oil in the radiator?
Not sure about this but I would drop the pan again and hook an air line up to where the sender screws into the block. Pressurize it to about 70 psi and see if you can find any obvious hissing.
It will hiss some from all the bearings but there might be one obvious hole.
You might rotate the crank a bit to line up the ports in the crank as I think it will fluctuate from zero to 60 psi as the crank turns and the holes line up.
There is an old school machinest here who has fixed a bunch of those 3/4/6 cyl oil lines that cavitated by using a reamer and then epoxying in a piece of brake line.
Not sure where it cavitates but he explained the process to me once.
 

[showcrop]

I'm pretty sure that I suggested to you before that while you have the pan down to remove one main bearing cap and plastigage to measure clearance to see how far out you are. Rods wear more than mains but it will still give you an idea. It takes just a few minutes with the pan off.
 

[Dave In Chattaroy]

Showcrop, I must have missed that suggestion but let me ask the question because I'm not familiar with the plastiguage measuring.....if either the mains or the rods are out of tolerance, I'm still looking at a rebuild correct? at least on the lower end?

Ultradog, there was no oil in the radiator
The cavitation that you're refering to, I'm assuming that it would cause a comprimise in the blocks integrity? I guess the idea of fixing a hole in the block would probably drive me towards a fully remanufactured engine. I'm looking for some longevity for the amount of effort involved in the R&R of this engine!

Thanks guys.
 

[showcrop]

[Bern]

So, if I understand you correctly, you have ZERO oil pressure, and yet there is oil coming from the pump at the filter location. Am I understanding you correctly?

If that is the case, then you have a MASSIVE internal leak somewhere, way more than worn bearings. Possible areas include a missing cup plug in the front, and the threaded plug in the rear of the oil gallery. Other possibilities inlcude a crack somewhere along a major oil gallery, but I would be at a loss to suggest where.

As for your theory of a plug somewhere, I really, really doubt that, unless someone injected super glue into your engine.

I have rebuilt literally dozens of those engines, and have never heard of a problem like that. I consider those lube systems to be fairly bullet proof.
 

[jkies]

worn bearings normally show good oil pressure at start up then less as engine warms up. some times heavier old will help. if this happened all at once then it's probably something else.
 

[Dave In Chattaroy]

jkies- after I replaced the oil pump and reassembled the tractor, when I started the tractor the oil pressure light was out initially.....and stayed out for about 5 minutes then came back on.......granted I had just refilled the oil and the barn temperature was in the teens.......

Bern- thanks for the info, Is the front cup accessible by removing the front engine cover?
 

[Bern]

Yes, the cup plug in question is behind the camshaft gear.
 

[Dave In Chattaroy]

Well since I've got to tear the front end off the tractor anyway to pull the motor and/or drop the sump....I'll now be checking that front cup as well!....thanks for the tip!