Packard Forum Index » V-8 (1955-56)

It wasn't the oil pressure sender at all. It appears to have been either the Valvoline straight 30 weight or the Marvel Mystery Oil it didn't like. (The MM oil was at about 30:1 ratio. Doesn't seem it would matter that much, and if it was just that, why didn't adding STP make any difference? Anyway, after changing out to the new oil pressure sender switch and having the light come on again, I decided to start at ground zero, changed to 30 weight Castrol "HD" and put the old sending unit back in. Whoopee! No oil pressure light!

I may have missed this in the long discussion thread, but if this was my Packard, I would temporarily install a mechanical oil pressure gauge. This gauge would tell me exactly going on.

Trying different oil weights and additives will not yield an answer. I use 15W-40 detergent oil in all my vintage vehicles with no additives. I think a 20W-50 oil is much too heavy and places too much of a strain on the pump. Using a heavy oil will not fix a low pressure problem.

Do you know what the trigger pressure is for the sending unit? It may be stamped on the unit.

Another thing to look at is the pressure relief valve in the pump. Some of us have had seen some improvement in oil pressure by installing a couple of shims under the spring. This "fix" improves running pressure, but not much of an improvement at idle.

Try a gauge and see what is going on and then you can act on this information.

Best of luck.

(o{}o)

I couldn't agree more with JW. If the sending unit is accurate and the OP light is on at anything more than a warm idle, you potentially have a serious problem and any further driving is bound to do damage. And the only way to know what's going on is to install a quality mechanical gauge - fiddling with different viscosity oils and additives is just folly. Most senders for OP warning lights trigger in the range of 7-10 psi.

Checking the oil pump relief valve (if you haven't done it already) is a good idea - a broken or severely weakened spring might explain everything. Otherwise, drop the pan and start checking bearing clearances.

PS - one other occasionally found reason for low oil pressure on the L8s is a badly worn oil pump cover plate, or too thick a gasket, or both. Simple to remove the cover plate and if it has a wear pattern from the gears then have it surfaced flat and smooth - what the wear pattern allows is for oil to short-circuit between the outlet and inlet and not continue to the oil galleys - ditto for too thick a gasket. Ross has covered this gasket thickness many times on these pages - THINK THIN, like notebook paper. Sorry if you've already been down this road, I haven't followed this thread fully.

I have a late '60s Olds 442 oil pump in my '55 and as far as I can tell, I have no problems with the pressure. I have recently developed other problems, though. I have at least one sticking hydralic lifter that chatters away when the car is cold and until I hit speeds of about 50 mph. This racket started back in late April and a change of oil hasn't made any difference. Reading the past submittals, it occurs to me that I may be using too heavy an oil, in this case, Joe Gibbs 15-50. I have been running about 6 quarts, which is slightly overfilled. On Saturday, I took the Clipper to Jiffy Lube and had them drain a couple of quarts out of it and add a quart of MMO. I haven't noticed any discernible difference at this time, but it hasn't been in the engine for long. I thought I'd run it with the MMO for about a month or so, then drain it and fill it with a lower weight oil, drive it again for a while and change it once again in Octobe, changing the filter with each oil change. Does this make sense to anyone?

Craig

Personally, I see no need for any additives if you are using a major brand of oil. An additive might even negatively affect the performance of the careful blend of lubricants and additives in the oil. I would use nothing heavier than a 15W-40 weight oil in the warm months and something lighter in the colder part of the year if you experience freezing and sub-freezing temps. You might get lucky messing around with additives, but I would not recommend any. Do you know which lifter it is and could the cause be something between it and the valve causing the lifter not to pump up? It is easy enough to isolate the cylinder and pull a valve cover and take a look. Good luck with the noisy lifter problem.

(o{}o)

SAE 15-50, for the climate of Virginia? Sounds to me like a really poor choice! 50 weight motor oil is about the same viscosity as SAE 90 gear oil - see chart; in my mind the concern would be the resistance to flow that the higher viscosity gives. Not that changing it at this point may solve your lifter problem. The often-quoted advice of running about 1/2 quart over full seems harmless and perhaps helpful, it should put the level at about 3/8 inches above the Full mark on your dipstick. Add more and at some point you run the risk of the rods dipping which will whip your oil into a froth!!

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There should be no need to overfill the crankcase if you have the Olds pump. The recommendation to raise the oil level was to keep the original Packard pumps from sucking air.

(o{}o)

JW Quote:

Correctamundo! In addition, the pickup for the Olds pump is at the same horizontal level as the gears right above the bottom of the pan since there's no vacuum pump in the way.

5qts of oil should be fine.

Craig

JW and all:

Thank you for your quite sensible advice. Frankly, ever since I started using the 15-50 oil the engine hasn't felt quite right. I plan to change it pretty soon and I think I will go with something like a 10W-30. I think it is good to have some detergent in the motor oil to prevent crud build up. Also, I agree that there is no need to overfill the crankcase. The car definitely runs best when the oil level is right at or just slightly above the Full mark.

Went out today to purchase some straight 30 wt. oil. None available, not even synthetic. So, let me see if I have this correct. Shell Rotella seems to come up often, only available in 15-30 synthetic. So, drain out the conventional oil, put in synthetic, and perhaps add a bit of Marvel Mystery Oil, and ZDDP? I know there is a bit of controversy about additives. If nothing else bring up the lead a bit with the ZDDP? 15-30 a bit thin?