F134 Oil Pressure

Hi All,

I know these types of questions have come up many times here so I apologize for redundancy, but I noticed the other while out in my 57' CJ5 that my oil pressure seemed a bit lower than what I think it typically runs at. Below are the stats for cold (just after starting) and hot (180ºF). I am currently running 10W-30 ambient temperatures are around 85-90ºC currently.

Cold Idle: 23 psi
Cold Peak: 60 psi

Hot Idle: 6 psi
Hot Peak: 18-20 psi

Two questions: 1) is 180ºF a little hot for a running temperature given my current ambient conditions and 2) is there anything I should watch out for regarding the oil pressure?

As always, thanks in advance for your guys' expertise.

 

Not too awful for an F-head of that age, IMHO.

In your ambient temps, maybe try a straight 30-SAE, or a 20-50? But 180º engine temp seems about right. (I think a 165ºF thermostat was OEM optional.)

To "watch out for....?" Yes, if the pressures continue drop further, I'd wonder if it was time to consider some replacement or .001" undersize bearing shells. Or start budgeting for a rebuild.

But with the numbers you have, I'd drive it. Just don't push it too hard at speed. My personal limit is 50mph on my '56.

PS- always consider verifying if your gauge and sender are functioning correctly, including having good wiring and clean tight connections and grounds.

 

Do you have a thermostat in the engine? Is it a 180 degree thermostat?

Cold readings mean nothing IMO. Oil viscosity will be high, and the pressure will be good. A starting rule of thumb is 10 psi for every 1000 RPM. You need enough oil pressure to overcome the rod velocity/force on the crank at the ignition stroke. Without enough OP, the rod bearing will contact the crank and the rod bearing will fail. The higher the speed, the more rod velocity and the higher the downward force.

IMO no reason not to go to a 15W40 oil like Rotella or Delo, or 20W50 Castrol. Even 40 or 50 single weight would be ok IMO - Valvoline Racing Oil is good. You'd only want something thinner if it was cold enough to make starting difficult against the thicker oil. I run the 15W40 year round in my Jeeps.*

* except the Cherokee. It gets 5W20 full synthetic, as spec'd for it.

 

Just saying, my F-134 with a fresh but broken in motor with a mechanical gauge, 10w-30 oil held 43-48 hot PSI at cruse speed. 18-20 PSI at hot Idle.

 

That's a very real thing, in seasonal climates. I once put a slightly heavier oil in an older car, then one morning I couldn't even make it crank over.

 

I need to check what thermostat is currently in there as it was put there by a previous owner after a rebuild.

 

This is good advice. First thing first I should verify the accuracy of my gauge. A 165º thermostat might not be a bad idea either.

 

Your warm oil pressure is a bit low. This may indicate wear from higher mileage, or could be from the oil being too thin. Try an oil change, switching to a straight 40w for warm weather use. I would expect noticeable improvement. I would want 35-40 psi as a minimum pressure driving at 45mph down the road.
-Donny

 

What’s the likelihood the oil pump is failing?

 

I have had that thought at times in the past, with high-miles engines. In my experience, replacing the oil pump made little or no improvement.

We can agree that, if nothing else, they are well lubricated.

 

Yeah, I figured. Given the fact that it’s a pretty simple mechanical part, it makes sense that it’s probably not the source of the problem.

 

I am at agreement . hot 6 psi
high-miles engines need thicker oil . 40W
lots of worn bearing surfaces . crank/rods/camshaft = loss of oil pressure

 

X2
While I suspect worn bearings (excessive clearances), the oil may be part of the problem.
IMHO, a 10/40 would be minimum for any of the older engines.

Given you have new oil in there, a can of STP or Power Punch would bring up the viscosity and help provide a better anti-wear film on the bearings.

 

I have been running 15/40 diesel oil for years. And add a quart of Lucas oil treatment.

 

x2, As Pete said, I have never changed an oil pump on a L or F- 134 that that made any difference. I have returned to service the oil pump from a totally worn out f-134 on a complete new rebuild. The new engine held perfect oil pressure. Ran for several thousand miles and sold it.

 

My impression that the oil pumps that run in a cast iron housing (like the F134 and 258) don't wear much. The ones that run in aluminum like the AMC V8s and the Buicks can be the source of low oil pressure. Typically you replace the iron pumps at rebuild time as good practice, but they are not the focus of wear. Just to mention it - the OP could pull the pan and Plastigage the bearings. Or not.

 

Timer. You are right a oil pump in a cast iron housing doesn't have the problem with wear because you think about it. It is pumping oil that is lube. The problem with buick and AMC engines is the housing is aluminum and the gears are steel.

 

Question regarding my fuel pressure gauge. Looks like the previous owner has a Stewart-Warner gauge installed. I think it’s this one:

https://www.stewartwarner.com/products/deluxe-oil-pressure-gauge-82322/

I see a plastic line with no sending unit? What’s going on here?

https://ibb.co/c26GXDh

 

"I see a plastic line with no sending unit? What’s going on here?"

It is a mechanical gauge, not electrical, so there is no "sending unit" the line connected to the gauge on one end and should be connected to a oil gallery port on the lower driver side of the engine block.

Stock gauge would have had a steel line coming from the gauge clamped to the firewall with a flex (rubber) line connecting from that to the block. With many aftermarket gauges they use plastic lines which connect directly to the block. I do not like the plastic lines, had too many of them spray oil out from under the dash after the line got old and brittle.

 

If you're lucky.
I lost one under the hood and didn't know it till the lifters started clattering.

This is why I'm such a BIG fan of idiot lights...........................

While not considered correct, I've run a copper line since the mid 80's with no issue.