Low oil pressure causes

[corelokt]

I have what may be low oil pressure. My gauge reads low, 30 psi cold, right near 0 warm, at idle. I say might because the gauge is electric and unproven. I put in an old mechanical gauge I had and it reads even lower, but it old, crusty and a cheapo besides.
This is the engine that lost its oil once. I pulled it and replaced the lower end bearings and put in ARP studs. I did not do anything with the cam.
If it is actually low, what would be the cause and cure?

 

[cucvrus]

You know the answer to that. You just told us. It needs replaced or overhauled. You could put heavier oil in it if it is not knocking. Remember oil pumps do NOT create oil pressure. it is the clearance and tight tolerances of the bearings that create the oil pressure. Oil pumps move the oil thru the oil system. I know what I man and know what I said. i will not get into a rocket science debate about it. You know that the engine was damaged when it lost oil. That happened almost instantly. Now you know what needs done. Good Luck. I don't envy the job. But it is doable and i would probably find another engine at this point. Once again GOOD LUCK I hope it all works out. But if it's not knocking don't worry about it. Keep looking for a replacement.

 

[ken]

Replace the gauge with a good quality unit like a VDO. If that does not work, replace the oil pump. They are not expensive. Is the oil level high? Does it smell like fuel? The lift pump may be leaking fuel into the crankcase and thinning the oil.

 

[corelokt]

The oil is full and fresh. Lift pump is electric.
The oil pump is fresh too.
It has to be in the engine.

 

[Tinstar]

Where are you tapping into the engine for the pressure reading?
You might try a different location (oil sample port) and see if any difference.

Agree on new quantity gauge. ISSPRO, VDO, AutoMeter are all great gauges.

Sounds like your putting off the inevitable though.
Total rebuild.

 

[corelokt]

When I put the bearings in the bottom end, I pulled the crank and had it checked. I also pulled the heads and the cylinders looked good. Valves were clean and looked right also. I'm wondering what other clearance issue would drop the pressure?
Btw, I'm hoping for crap gauges. The electric is dat-com with the matched sensor.

 

[porkysplace]

When I put the bearings in the bottom end, I pulled the crank and had it checked. I also pulled the heads and the cylinders looked good. Valves were clean and looked right also. I'm wondering what other clearance issue would drop the pressure?
Btw, I'm hoping for crap gauges. The electric is dat-com with the matched sensor.

Did you [FONT=Arial, Helvetica, sans-serif]PLASTIGAUGE the bearings or just throw it together ?
http://www.plastigaugeusa.com/how.html[/FONT]

 

[corelokt]

Took it to a machine shop.
Even the bearings looked ok. Not perfect, but not bad.

 

[cucvrus]

When you say lost oil. All the oil? I am thinking cam bearings but hard to say. What symptoms do you have? If you were unknowing and did not have a gauge just the stock light. Would the oil light be lit at anytime driving or idling. If you answered no. I would run it and just check the oil. Do you see more then normal metalic content in the oil. Maybe an oil analysis is in order. I had one done to a CUCV engine once. Right after I bought mine back in mid 90's I would get a loud knocking sound and it would go away. So I sent a 4oz oil sample to Pennzoil for analysis. it came back fine and the mileage estimate on the engine was within a few thousand miles of actual mileage. There estimate was lower. Good for me. Come to find out the occasional knock was a delivery nozzle that would hang up. Gives you a real scare at 70 mph on the I 81. But all is well. Hope you get this issue worked out. I have a few rebuild-able low mileage short blocks you could get rebuilt and keep running the other one till it's ready. You have good heads from reading your posts. Just an idea. You are i skip and a hop away. I am at 90MM on I81 in the Keystone state. Let me know. We can trade. i like anything automotive/truck related.

 

[ken]

Try A good quality gauge and report back. There are high volume/pressure oil pumps on the market that may flood parts that have extra clearance to help bring pressure back up.
But Id bet its the gauge. Also what pressure is your electric lift pump at? I had a electric lift pump that over pressured the IP and blew fuel into the crank case from the shaft seal behind the timing gear. I threw it in the trash and installed a mech lift pump. Check the oil for fuel contamination. Also Check the oil filter bypass valve. It's under the oil filter. These hardly ever get cleaned during a rebuild.

 

[corelokt]

Thanks! Good to know spare blocks are near. Monday it goes to a good diesel mechanic. Due for the timing to be set. I'll ask him to do an oil pressure check. Hoping he can stop my braided stainless oil cooler lines from dripping and get one last oil pan bolt in. Had the pan off and the rear right bolt wouldn't go in. Tried chasing the threads but it took the threads off my cheap tap. Tried beveling the bolt, no go. Everything on this engine is the best I could get, and fresh. I think it was a high output oil pump, but I'm not sure. It's a Ted's take out hum vee block, hate to give up on it.

 

[corelokt]

Oh, ordered an IH tractor screw in oil pressure gauge. I'll put it in the OEM spot, where I have a npt manifold for the gauges, light, etc. 0-45 psi range, that and having the IH logo are why I like it. No light opening either.

 

[porkysplace]

Took it to a machine shop.
Even the bearings looked ok. Not perfect, but not bad.

So the machine shop put it together ?

 

[corelokt]

It was mic'd. I put it together. All new bearings, the studs, torque sequence etc. Why? I know the bearing oil holes are right.

 

[rchalmers3]

I might be ignorant of the multifuel design, but most "cam in block" engines have cam bearings also. You could have wiped those, thus your low pressure.

Rick

 

[corelokt]

Wonder what that would cost to have fixed? I'll bet it's more than that pressure gauge even.

 

[porkysplace]

It was mic'd. I put it together. All new bearings, the studs, torque sequence etc. Why? I know the bearing oil holes are right.

Because even if you mic'ed all the new parts you still don't know how many thousandths clearance you have once they are torqued down.

 

[corelokt]

I didn't mic the new bearings. I had the crank mic'd. It was good as was and I used OEM spec bearings to fit it. Why would I use under size bearings on an OEM journal?

 

[porkysplace]

I didn't mic the new bearings. I had the crank mic'd. It was good as was and I used OEM spec bearings to fit it. Why would I use under size bearings on an OEM journal?

A brand new crank and bearings can be out of spec once bolted together , they can by to tight or to loose . The rod and main bearing journals also effect the clearance of the bearings . That is why you need to plastigauge each bearing and record the findings to see if they are within allowable clearances ( covered in the motor rebuild manual) . Tight bearing are easy to tell as the crank usually turns hard by hand , loose bearing are only not by checking the tolerances or by lack of oil pressure . Yes it is a time consuming process but the only way to know if your crank and rod bearings are correct . even the Haynes manuals sold at AutoZone have the specs in them.

 

[corelokt]

It's off at an actual diesel shop with a lift and everything. I asked him to look into it. Will let you know.