Uh Oh! Low oil pressure

Well, crud!

I got my electronic Autometer gauge in my '73 (351C, 2V) last night, and when I started the car up, it registered about 65 psi. After it was thoroughly warmed up, I was getting about 15 psi at idle in park . It was lower when the car was in gear. When I stand on the gas and rev it up to over 3K rpms, it gets over 30 PSI and approaches 40, and it doesn't spike, but it goes up slowly. Traveling at about 60 mph, it registers a solid 25 or so psi.

Should I be looking to get a new engine or rebuild? This sounds like very low readings to me. I really don't hear any bad sounds from the motor that sound like rods knocking or main bearings....but I'm still worried.

Thanks,

Joe

A general rule of thumb is 10 psi for every 1000 rpm, so it sounds like you're in the ball park. Electronic gauges are dampered so that the readings don't jump around, which may be why you're seeing the gradual climb.

A mechanical gauge will usually give you better information, and can also indicate when your main bearings are worn. If, when you are accelerating, maintaining speed, or decelerating and the pressure changes at the same speed/rpm you likely have some bearing issues. Usually, electronic gauges are too dampered to show much, if any immediate change.

Well, crud!

I got my electronic Autometer gauge in my '73 (351C, 2V) last night, and when I started the car up, it registered about 65 psi. After it was thoroughly warmed up, I was getting about 15 psi at idle in park . It was lower when the car was in gear. When I stand on the gas and rev it up to over 3K rpms, it gets over 30 PSI and approaches 40, and it doesn't spike, but it goes up slowly. Traveling at about 60 mph, it registers a solid 25 or so psi.

Should I be looking to get a new engine or rebuild? This sounds like very low readings to me. I really don't hear any bad sounds from the motor that sound like rods knocking or main bearings....but I'm still worried.

Thanks,

Joe

Click to expand...

Pretty common in a old Ford imo

I'm going to monitor it closely, and maybe switch to 20w50 or 30 weight oil. It's got 10w40 in there now.

Is it tough to change the oil pump on these motors?

My 5.0 has registered zero (on the stock gauge) at idle since I bought it 25K miles ago. tried different oil viscosities, makes little to no difference when hot. Has no knocks or ticks, pressure rises with RPM.

No worries.

IMO, it's nothing to worry about or do something about (like changing oil pump or viscosities). If the performance is satisfactory, leave it alone. However, if the oil pressure decreases significantly or disappears, you'll know it's time to take action. For now, though, I don't see a big problem.

Doc

PS Changing the oil pump is a real PITA, requiring hoisting up the motor to remove the oil pan, etc.

It sounds like it has a lot of miles on it or it was run too low on oil once too often and the clearances of the bearings and or the oil pump has opened up a bit. The Ford manual calls out oil pressure at operating temperature and at 2000 RPM to between 50 and 70 PSI. If you are driving it "normally" it will probably be fine as long you don't hear any knocking when revved or all the lifters rattling at idle. Changing the pan is a bit of a pain but can be done. Unless you just want to take the engine apart, I'd drive it and watch for any changes in oil pressure and or ugly noises. Chuck

PS the only complete failure of an oil pump I've experienced on a car I owned was a 1990 5.0 mustang. The OEM pump housing is aluminum and the rotors are steel. Don't ask me why. At idle he rotor seized to the housing and twisted the oil pump drive shaft in half. A quick shutdown and a rollback wrecker prevented any further damage.

Lifter noise would be tapping on the top side of the motor, right? If I remember correctly, a rod knock would make itself heard after a decrease in RPMs after sustained high speed running.

The only sound I hear that could be taken as a tapping is coming from underneath the car. I had been figuring it to be a small exhaust leak.

I guess the motor does not actually have 60,000 miles on it if it's got this kind of low oil pressure.

Did you install a new sender with the gauge. I've seen senders go bad and give false readings. With that being said, as long as you're not hearing lifter or rod noise, as mentioned earlier, and you're not pushing the engine real hard, you should be ok for now.

Steve

Lifter noise would be tapping on the top side of the motor, right? If I remember correctly, a rod knock would make itself heard after a decrease in RPMs after sustained high speed running.

The only sound I hear that could be taken as a tapping is coming from underneath the car. I had been figuring it to be a small exhaust leak.

I guess the motor does not actually have 60,000 miles on it if it's got this kind of low oil pressure.

Click to expand...

The lifter noise would be several rapidly occurring, near simultaneous pronounced clicking sounds. A rod knock is usually less rapidly occurring, deeper in the engine, and sounds more like an actual knock. Simulating sounds with words is difficult, sorry if I'm not clear. It may have 60K miles on it. A lot of things affect engine life, how hard it's used, how it is maintained, fuel contamination due to rich or flooding carb, etc. In the old days engines didn't last as long as they do now. Advances in fuels, fuel injection, electronic ignition, and engine design all contribute to a modern engine lasting a lot longer.

My car has read 5 psi at idle for all 8 years I've owned it. Engine was new when I bought the car. Beat on it hard over the years and no problems.

Like others have said I think its common in older ford engines.

Again, Thanks for the info.

My only experience with internal engine stuff is with my old VW motors, but I definitely know what a rod knock sounds like, as I've thrown rods in those motors before.

VW's are also well known for valve/lifter noise, and I always set my valves loose, so I think I have a good bead on that too.

I think my Cleveland sounds OK, as do others I've talked to, so at this point, I'm going to chalk it up to it being "an old Ford", and move on to other issues (I've got a million of 'em.)

My car has read 5 psi at idle for all 8 years I've owned it. Engine was new when I bought the car. Beat on it hard over the years and no problems.

Like others have said I think its common in older ford engines.

Click to expand...

I think my Cleveland sounds OK, as do others I've talked to, so at this point, I'm going to chalk it up to it being "an old Ford", and move on to other issues (I've got a million of 'em.)

Click to expand...

So what is next on your list?

I think next up is going to be seeing if I can't get that transmission leak under control, but from what I'm reading, c-6 trannies just leak. After that, probably the temperature gauge, and then maybe starting on the suspension.

As soon as it warms up, I'm going to start trying to buff it with some high cut compound to see if I can't smooth it out a bit.

I think my Cleveland sounds OK, as do others I've talked to, so at this point, I'm going to chalk it up to it being "an old Ford", and move on to other issues (I've got a million of 'em.)

Click to expand...

So what is next on your list?

Click to expand...

Good decision on letting the oil pressure ride. The only way to get the pressure up is to install all new engine bearings, including the cam bearings. A new pump is not likely to help since a pump just moves the oil. The bearings create the resistance to flow which causes pressure.

The best way to get the C-6 to stop leaking is to replace it with a 5 speed! LOL

not a fan of elec oil pressure guages, i would be interested in what readings you would see from mech guage.

To breath life into an old thread, because I'm dealing with these same issues in my car.

I've hooked up a Mech Gauge in place of the electrical one (I didn't trust it) and I get a solid 10PSI at idle, and it builds smoothly to about 40PSI at 2000RPM

I'm running 5W-20 oil which I think is a little too thin for these engines, next change I'm going to step up to a 10W-30 I think.

But the point of this post is, if I sustain the engine at a higher RPM, say 3500RPM or so, I get a pretty good clacking noise from the engine. I would say maybe it's noisy lifters? But I have no experience in this area. As soon as I let the engine come back down to idle the noise goes away, after about 2-3 seconds, and doesn't return until I sustain that higher RPM for about 45 seconds or more, not instant.

So what should I do? What can I check? The engine only has 20K miles on it, but it's spent a lot of it's life sitting unattended.

Is it a heavy clunk like pounding on the side of the block with a hammer?

No its more of a light clatter, more along the lines of noisy lifters. Its hard to describe. I haven't adjusted the valves since I got the car, I may just need to do them