Packard Forum Index » Post-War (1946-54)

As Laughlin attendees know, my 53 Clipper Dlx had some electrical and oil light gremlins. I got her home safely, but the oil light still goes on intermittently. Using a mechanical gauge, I got the following readings:

idle at start: 26 psi
idle when warm: 27-28 psi
oil light is on at idle

oil pressure when revved up: 34-38 psi

Is this low? Should I be concerned? Is a rebuild of oil pump recommended.

I'm running Wolfshead 15-40 synthetic blend.

Thanks

One might wish it was a bit higher at warm road speeds but I think it's still quite adequate. 28-28 psi at warm idle should not be enough to trigger light so you may have a failing sending unit. Do I assume the light goes out with just a tickle of the accelerator?

In any case if the pressure were truly low, the most likely cause would be bearing clearances and not the oil pump.

I don't know if electric oil pressure gauge switches are still made to come on at different pressures like they used to. I recall seeing switches with 'on' pressures of 4 lbs to around 10 lbs. Seems one would want a switch with the highest rating as a switch with a low pressure rating might not come on until damage was caused by too low oil pressure. The infamous "Your Engine is Junk" light.

(o{}o)

As Owen states bearing clearances is a very good reason for low oil pressure. But first check things that have caused previous problems. In the September 1946 Service Counselor it talks about loose wiring Connection or bad ground could cause a low pressure reading. Also use a manual gauge to verify that your Electric Gauge is reading correctly.
And do you know when was the last time the oil pan was removed and cleaned? Also when was the last time your Oil Float Screen was cleaned, because the November 1953 Service Counselor talks about loose tube nuts for the Oil Float Screen (Oil Sump).
Plus the January 15, 1947 Service Counselor has a good check for oil pressure problems.
I hope this helps, let us know what you find.
Wes

Oops! My bad! I reread and saw you did use a gauge, so go with the check of the oil pan and float screen.
Wes

JW brings up a good point. Too low a switch rating and the damage is done. RockAuto lists the replacement as a Standard PS15 sender in the 3-9psi range. That crosses to a Napa ECH OP6613 which is even worse at 2-6psi. I think those pressures are too low.

There has been successful use of the Rebco 1401345http://www.rebcoperformance.com/catalog/item.asp?id=134&catid=5 as listed in the parts xref. That one is rated at 20 psi and I think a more reasonable value. Napa has the ECH OP6741 rated at 15psi which is in a better range and form appears to be a direct swap. They also have a couple slightly higher ranges that would match the Rebco but like the Rebco, the terminals are different.

Any of the 15-20 psi senders might be worth a try in case yours is failing or someone has put too high a value sender in.

Another thought occurred to me. Assuming the pressures you obtained with a mechanical gauge are accurate, the excellent pressure at idle suggests the road speed pressure should be in the 40+ range. Your oil pump has a pressure relief valve to "dump" excess pressure and it's controlled by a spring which perhaps has fatigued. Removing the access cover (looks like a large hex-head bolt at right angles to the pump body) and just shimming the spring with a washer or the proverbial thin dime might very well show a significant increase in the pressure obtained at road speed. Easier to shim the spring than try to find an OEM one, though a little trial and error might be involved in finding the right amount of shiming.

Good suggestion O_D. I shimmed the oil pressure relief valve spring in my 47 Custom with the 356 engine and gained about a 20% increase in pressure at all speeds.

(o{}o)

Lynn, here's what your owners manual says, that is if I'm looking at the right model and also the Engine Service Manual says 40 psi at normal driving speed. To me the readings don't look that bad but that's my opinion.
Flicking lights make me nervous also.

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Thanks all: the problem seems to be solved. I replaced the sending unit and not even a flicker at idle.

Thanks again