Dropping oil pressure

[Echomirage]

my burb has only had around 20lbs of pressure when driving normally. is that normal? last weekend, at a red light, it dropped to 0, and the check gauges light came on. i had to shift to neutral and keep the revs up, to keep pressure up. it does this about every time you come to a light and idle.

could the pump be going? could it be sludge in the pan, clogging the pump, or perhaps an oil galley somewhere? im the 3rd owner, and the 2nd owner did VERY little in terms of maintenance, so there could have been very, very long intervals of sitting between oil changes, so sludge could be an issue.

at my last change, i added a quart of seafoam, and the weekend prior to the dropped pressure, i did some moderate wheeling. could the seafoam, added with the extreme angles from wheeling have knocked some sludge loose, and maybe clogged the pump?

i was planning on dropping the pan, taking a look, and maybe swapping a high volume pump regardless, and hope for the best.

is this a problem with big blocks? anyone have this before?

 

[Dylan1991_1500]

If the engine isn't making terrible noises I would bet it is your oil psi switch going bad. Mine does the same thing.

 

[jkeaton]

If possible, put a mechanical gauge on it to verify.

 

[SAATR]

As stated, verify with a mechanical gauge before you tear into it. If the mechanical gauge confirms low oil pressure, I would pull the oil filter and cut it open to see if you have any bearing material present in the filter media. Use a razor knife to cut a swatch of material out, maybe 6 or 7 pleats, and then squeeze the oil out of it in a vice. Any bearing material will be obvious. If you find debris, drop the pan and pull at least one rod and main cap and inspect the bearings and journals. If the bearings are toast, but the journals don't have any serious discoloration or scratches you can feel with your fingernail, then roll in a new set of bearings and install a new pump. Pull the valve covers and intake and clean out as much old oil as possible. If your oil pressure is good after this procedure, do a couple of short oil changes with cheap oil and cut the filter after each change. If you find little or no debris, you may have dodged a bullet. If you still have debris, the failure may have been valvetrain or cam bearings and you have a choice to make. Pull it or run it. Good luck.

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[Ironhead]

As jkeaton said, the first step is to confirm the pressure with a known mechanical gauge. If the pressure is fine, then a new sensor is the next step.

If the pressure is low, and since you are planning to pull the pan anyway, I would say that it is possible that sludge could block the pickup. I have had personal experience with this problem when I bought a 1937 Ford that had sat for a number of years. Cleaning the pickup restored the pressure.

 

[Echomirage]

i can do alot, but bearings i think are a bit beyond my abilities. anything other then internal motor/trans/rear work, i can handle. im really hoping for either the switch, or a pump swap will fix it. ill try and find a mechanical gauge.

the last thing i need is a bad motor in this truck. i havent even towed anything with it, and thats the main reason i bought it.

 

[SAATR]

i can do alot, but bearings i think are a bit beyond my abilities. anything other then internal motor/trans/rear work, i can handle. im really hoping for either the switch, or a pump swap will fix it. ill try and find a mechanical gauge.

the last thing i need is a bad motor in this truck. i havent even towed anything with it, and thats the main reason i bought it.

Auto parts stores should rent a pressure gauge and adapters to check your oil pressure. Doing that and opening up the filter will give you a fair assessment of the internal health of the engine. If the gauge confirms a bad pressure sensor, then you needn't go further.

As far as rolling bearings go, it's a simple and straightforward task. Just requires patience, cleanliness, attention to detail, and cleanliness. Can't overemphasize that. If nothing else, pulling a rod cap and main cap to inspect the bearings requires nothing but the right size sockets and an accurate torque wrench.

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[Echomirage]

are the bolts torque to yield, or can they be reused?

 

[SAATR]

They can be reused without issues.

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[Ironhead]

There are more than a few stories of the Okies driving out to California in the 30s changing rod and main bearings in their Model As and old Dodges at the side of the road. They did not even use torque wrenches, but those flathead iron engines were not that sophisticated, so they could get away with it. After the bearing work, they often poured the old motor oil back in the engine!

Hopefully, nobody on this forum operates that way...