Packard Forum Index » V-8 (1955-56)

I had a major rebuild on my 56 Caribbean done. After the rebuild everything was fine, good oil pressure (middle of the gauge). After about 300 or 400 miles the pressure started to drop to 0 when the car was stopped and back up to normal when moving. Checked it with a mechanical gauge and I get the same readings. No lifter noise. It also takes a few seconds to for the gauge to move after the engine is started. The person working my the pump thinks is the problem is the relief valve. He noticed that when he turns the shaft backwards oil squirts out the vacumn vent (as explained to me my him)and he doesn't think that normal. Any thoughts? The oil pump was a new replacement.

Here is what you will hear..... Do the olds oil pump conversion. Long story short.

It also takes a few seconds to for the gauge to move after the engine is started.

Typical of resistance-type pressure gauges. The test with the mechanical gauge should have given an instant response.

Grasp the shaft sticking out of the top of the pump and move it sideways to check for wear. Any good mechanic knows how to do this and can estimate the wear. Otherwise take it to a seasoned machinist and let him 'feel' for the wear. IIRC the service mnaual indiacates 0.004" service litmit for wear (which is a bit high).

Does the pump have an OPEN pressure relief valve port or the very late 56 pump with PLUGGED pressure relief port???

We don't know which oil pump it is. It should be for the later 56's, the car is one of the last made (1260). The number on the casting is 6492430. This has a cap on the bottom of the relief value bore (as explained to me). Also it take two or three second to indicate oil pressure with the mechanical pressure gauge also. It's seem like when the engine is turned off all the oil is draining back into the back.

THere is a number of possibilities causing the symptoms. The pressure relief spring could be faulty but that usualy causes low oil pressure as engine speed increases too. Could be a sticky or faulty pressure relief valve (like a little piston).

At this point u can either send the pump back to the rebuilder or disassemble the pump for an inspection.

First thing i would do if i had the pump in my hand is to check the wear at the input shaft. THere are some mechanics that can do this with reasonable accuracy of determining wear.

THe problem reported COULD be NOT pump related. Loose rod or main bearings, mite need LATE cam retainer, mite have early 55 rockers. Other possibilites.

If u decide to disassemble the pump for inspection we would all like to see pics of the parts and maybe we can determine the problem here. Otherwise u'll just have to take the mechanic and the vendors word/advice.


Edit: Note that the pressure relief valve piston for the LATE PUMP seems to be unobtainable. IT is NOT the same relief valve as used on mid-56 and earlier pumps nor is the spring.

To ACTUALLY SOLVE the oil pressure problem, buy and install the Olds HV oil pump conversion. You've obviously had the oil pan off at least once, so the conversion is straight bolt-on from there.

Jack Vines sells it: packardv8@comcast.net

Craig

Dear Don:

Standard practice is to use a new oil pump with any new motor, unless such is not available.

Rebuilt Packard pumps are expensive, but considering all the parameters, if there is an off the shelf alternative (Oldsmobile) then that is a good choice.

Motors are too expensive to compromise for the sake of an oil pump.

Hope this helps

Thanks for all the advice. The person working on the problem was called away on a emergency job and probably won't be able to work on in till after the holidays. I'm at the point now that if he can't find the problem I am going for to Olds option. I've relayed all the info to him and I'll wait to see what happens. Thanks again and I will let you know if he actually finds and corrects the problem.

My 55 patrician has developed an oil pressure issue. I changed the oil, using Castrol 10W-30 conventional with the C-4 Fram filter and noted to my satisfaction that the oil pressure increased by about one quarter. The next day the gauge showed one quarter less so I drained a quart and topped it off with Lucas heavy duty oil stabilizer. Simple fix I thought and the pressure was back up. The next day the pressure is down again. Should I have used the C-4P filter instead and 10W-40? I live in Florida and it is like 80 degrees today. The engine runs very smooth without any lifter noise (they were changed last year).