Steves Buick

loss of oil pressure

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Hi guys, 

I just took my 1932 96s out on its first drive since restoration, ran great until 55 mph then the oil pressure started falling off to about 5psi. 

There is no external evidence of leakage, I have 2 oil pressure guages but T from the same source from the bas of the block. Any ideas before I drop the pan and check the screen? 

Thanks,

Steve

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I'm not familiar with that era Buicks but my guess, assuming you still have sufficient oil in the crankcase, would be failure of the oil pump pressure relief valve, assuming it has one.

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Check to see if there is an oil pressure relief valve and if it is stuck.

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Does it have a bypass oil filter? If so, it needs an orifice to regulate pressure and volume through the bypass filter. Common issue on rebuilt motors on start up. I have seen it a dozen times. Be careful, and use an oil pressure pot if you don’t find anything obvious. If you missed a line, cracked a line, or some other internal issue, a pressure pot is the only way to find it.

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2 hours ago, edinmass said:

use an oil pressure pot

Can you expand on this new term for me please.

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Posted (edited)

An oil pressure pot............A pressurized tank, filled with oil......3 to 6 gallons, and adaptor lines to place an external oil source with pressure too pre lubricate and engine before start up, as used on many aircraft engines from the 20's to the 50's. It will allow him to see oil flow at every spot in the engine, BUT any open gallary, cracked line, or large leak will be apparent right away. All while making a HUGE mess......I have special pans for my lift. When starting a exotic engine for the first time....like a Model J, we use it to flush the engine BEFORE start up Ed

 

Looks kinda like this...........item shown is not an actual unit, but similar.

oilpot.jpg

Edited by edinmass (see edit history)
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Thanks, the oil pump does have a pressure relief valve and also a by pass valve to regulate oil flow to the oil temp regulator. Love that oil pressure pot!!! but dont have one, remember I had good oil press before it dropped off. Any thoughts on trying to unseat either the pressure relief valve or bypass valve by reverse press through the oil temp reg pneumatically? And I agree that dropping the pan is cheap insurance.. good call there.Thanks

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Having good pressure and then a drop off is going to be just one of a few possibilities. Oil pressure relief / bypass valve, internal oil line crack/leak/failure, or for some reason and oil gallery plug coming out. On many high end cars, the pressure regulator and bypass valve are external, making any repair much easier. Take your time and figure it out, guessing can be expensive and time consuming. 

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are you sure the pump is producing the proper pressure         have a 32 plymouth       motor rebuilt   last year        pump was rebuilt in 70s by a well respected source that advertises on this forum      same like your car        good pressure but as soon as the oil heats up pressure drops      rebuilt the pump myself with new gears   and the problem is now solved

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Thank you Guys,

I'm taking a break for a day or two, that seems to help for some reason.. I wish my pressure relief and by-pass valve were external! I'll take my time and get it sorted. yep broker-len sure the pump was producing pressure but not now as I have 2 oil pressure gauges. looks like I will drop the pan and pull the pump next,  thanks edinmas , hopefully no internal breakage. I'll keep you posted.

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One horrible possibility is that you burned out a bearing. What is in the pan will tell you if that has happened.

Hopefully it is just some crap in the relief valve.

Sudden reduced pressure, with some pressure remaining, points to the valve.

If the pan is really gunky, I have seen a plugged screen casue sudden pressure drop. A failed pump, you'd have no pressure.

 

Good luck. (That pan weighs a ton).

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Steve,

If the bottom plate on your oil pump looks like this (mine), emory it down with 60, then 120 grit till all the dark spots around the perimeter are just GONE.

Put a THIN coat of Permatex #2  around the edge and seal it up.

Distance between the gears and bottom plate should be NO MORE THAN .005"

 

Did mine 5 years ago and she still holds 40 # at a hot idle.

 

Mike in Colorado

035.JPG

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 Thanks Mike and Don,

Looks like the pressure relief valve is the most likely culprit. Don I'm hoping its just a clogged screen like you mention. Well see Tomorrow when I drop the plan. And good tip about the weight and clean up with emory cloth. 

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Posted (edited)

Look closely at all pump system control springs. I had  a customer car with low oil pressure. Found that the relief valve spring broke off a few end coils and with pump pressure, the pieces threaded together making the spring shorter.  Didn't notice it until I gave the parts a good cleaning. Old springs can become work-hardened and break.

 

They can also become compressed by use and thus give weaker oil pressure.  Check the spring length if you have info what it should be.  And cleaning can cause an old, weak spring to not give as much tension. Held in place by decades of crud, they seem to hold pressure fine. After a good cleaning they no longer have crud to help hold them - they can move more easily and suddenly don't hold as much pressure.

 

Also, changes in oil viscosity will change oil pressure. You haven't mentioned what  rating of oil are you using ?

 

Paul

Edited by PFitz (see edit history)

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Thanks Paul.

Will check the springs, I ran it on 5-40w Castrol non synthetic, changed out to straight 30W with 32oz of Lucas oil additive trying to thicken things up. 

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Steve. Ok, that all should have given decent pressure readings if the pump system was good.

 

Good hunting - I hope you find the problem and it's something easy to fix.

 

Paul 

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6 hours ago, Steves Buick said:

changed out to straight 30W with 32oz of Lucas oil additive trying to thicken things up

I think you mean SAE 30? SAE 30W is a different oil. So what viscosity do you think you have now? Why not use a 5W-50; at least you would know what you have. At the moment you are guessing. In addition, your oil is very viscous at cold start and you might see a high pressure but not get much oil delivered, so wear will occur.

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Steve,

Old used car trick, back when cars had oil pressure gauges, and came in with low / no pressure showing, was to pull the pump and stick a 3/8" nut behind the pressure relief spring.

Of course we also turned the speedo's back quite a bit too.

Can't do that now, 'cause it is all electronic.

Ah, the "good old days".

 

Mike in Colorado

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Ok guys,  wait until you see these pix, I have a broken line that was work hardened due to the cotter pin  on  the connecting rod hitting the main bearing pressure line. The pan was fairly gunky, the screens not so bad, pressure relief valve and spring in good working order.

The pix are pretty self explanitory, now I really need good opinions and suggestion on the fix, any one have a spare line laying around..  I feel lucky in a way that this didnt happen far from home as the line was destined to fail. New rings were installed in 1979 and thats when the  cotter pin started hitting the line. 

Thanks everyone for the help. All ideas and suggestions for the repair most welcome..

Steve

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WOW.......talk about dodging a bullet........ :o

 

As for fixing you can likely salvage the Tee part.

The rest is pretty easy.

If you aren't an expert at soldering.......find someone who is.

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Posted (edited)

Yes, very lucky.

 

I would use silver solder to fill that  wear groove. It will strengthen the remaining copper enough to easily hold up to oil pressure.

Then I'd sweat-fit a new piece of tubing into that tee.  

If you can't salvage the compression nut off the broken piece of tubing and anneal and re-expand the flared end so that it will fit onto a new piece of tubing, then replace it.

 

Paul.

Edited by PFitz (see edit history)
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Agreed.

 

Real silver solder by the way, meaning hard solder, to fix the groove, not some soft wire plumbing solder with a little silver in it.

 

 

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Thanks Bloo, I should have clarified that.  Not "silver bearing" plumbing solder, but high strength, high-content silver solder,  such as  this Harris Safety Silv.

 

https://www.amazon.com/Harris-Safety-Silv-Silver-Solder-Brazing/dp/B0713Y6V2F/ref=as_li_ss_tl?ie=UTF8&qid=1509821265&sr=8-1&keywords=harris+56+silver&dpID=41nWWWL1eXL&preST=_SX300_QL70_&dpSrc=srch&linkCode=sl1&tag=herafan-20&linkId=79a7c4a34eec6a14745532ba2ded41c4

 

Here's the flux to go with it.

https://www.amazon.com/Harris-SSWF1-Stay-Brazing-White/dp/B002075B0U/ref=as_li_ss_tl?ie=UTF8&qid=1509821194&sr=8-2&keywords=harris+stay+silv&dpID=51DC1CJc%2ByL&preST=_SX342_QL70_&dpSrc=srch&linkCode=sl1&tag=herafan-20&linkId=49d4461d9c3d45c7181a6ccba93377bd

 

And you can also use that for the sweat-fit joint.

 

And you might need the higher temps of a MAPP gas torch to get the solder to flow properly into a fully cleaned and fluxed joint, rather than just a propane torch.

 

Paul

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I believe the technical term for silver soldering or hard soldering  is "silver brazing".

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