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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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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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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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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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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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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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How hard would it be to make a new one? I don't see anything there that isn't commonly available and then you wouldn't have to worry about that thin spot coming back to haunt you. You're still going to have to fix that broken stub and sweat at least that joint, and doing so will possibly cause the others to come loose. I'd make an all-new pipe and know that it's done right. I might even use something like Cunifer (copper/nickel) tubing instead of the copper. Cunifer doesn't work harden from vibrations the way copper does. Plus if you make a new one, you can bend a little extra clearance into the areas where you need it.

 

A little extra work, maybe, but you don't want to take a chance with oil supply and you only want to do this once, right?

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Thanks Bloo, Paul, Don, Matt and Mike and everyone for the advice and links,

 I'll fab one up, but the tubing flare at the end of Bnut could be a challenge, early dole fitting??  Really like the Cunifer idea Matt, and yes I  only want to do this once. This forum is a life saver.. mucho grats.

Steve

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On 6/28/2019 at 1:00 PM, edinmass said:

 obvious. If you missed a line, cracked a line, or some other internal issue, a pressure pot is the only way to find it.

 

 

Nailed it! 👍

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Those "threaded sleeve" tubing nuts are hard to find, but available. I would try like crazy to save the original. It does look a little different than current ones. You would really want to look at the threads and angle before replacing it, just to make sure. I would cut off the tiny bit of tubing sticking out the end, as it will be slightly larger. These tubing nuts bite into the tubing a little bit, so the tubing becomes a smaller diameter right where the flare end of the nut is. You'll have to get rid of that end bit to get the tubing nut off.

 

What size is your tubing? Midland Metals makes those nuts, and Blackhawk Supply has them in at least 3 sizes. I bought 5/16" for my Pontiac fuel lines.

 

 

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That main galley line is probably brass, not copper.   OnlineMetals has brass tubing.   The point someone made earlier about the orifice in the filter line is something I ran into while restoring my 60 series car.  My car had the fitting replace with a much freer flowing fitting and I caught it which is probably a good thing since the engine had about 15 minutes run time on it after a compete overhaul.  The correct fitting is for double compression line, has a dog leg and one branch that feeds the oil filter and other feed the instrument panel oil pressure gauge.  That fitting has the Buick logo stamped or cast on as shown in my picture below and the orifice is sized to feed 1 qt. of oil/5 minutes to the rocker arm shaft at 25mph PER the 1931 Buick Specs and adjustment manual.  Assuming you have the base fitting already that screws into the block you just need to find the branch fitting.  A larger or less restrictive fitting will over oil rockers and front generator bearing and the pressure loss that allows it to flow freely is taking oil pump capacity from mains and rods.   If you have gray muck in the pan carefully inspect main and rod caps for any discoloration that may indicate the bearing got hot.  If in doubt, plasti-gage the bearings.

OF 002 (2)_LI.jpg

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 I drove the car today!!  I ended up silver brazing a sleave over the broken fitting, it took a few trys to get it all in alignment perfectly but I did. I extended the length by 1/8 in and put a slight bend downward of the most forward fitting to make sure I had clearance from the connecting rod bottom. I also placed 2 flat washers in the oil press relief valve end against the spring which brought my press back to 35psi at all speeds. Of course today was warm and my marvel was acting up a bit running rich, so I'll dial that in this week.  All in all I'm pleased with the out come. Thanks to all for the help, Ill post a pix when I get my phone charged!  

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  • 2 weeks later...
On 6/30/2019 at 10:57 PM, FLYER15015 said:

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

You need to be sanding these kind of things on a "surface plate" - a chunk of metal that is actually flat (most good machine shops will have a surface plate) - and you can home try it on a large anvil or block of metal, but ..  

Edited by John_Mereness (see edit history)
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A piece of plate glass on top of a piece of plywood is one way of guaranteeing that the surface is actually flat.  Valve grinding compound and a figure eight motion works great.

Also works great on water outlets and water manifolds.

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Surface plate, surface grinder, and do NOT put any sealer on that at all. 

 

 

 

PS.......glass is not flat over a large area.........for very small parts it’s ok. 

Edited by edinmass (see edit history)
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Actually, I did mine on my Bridgeport mill table.

And just to check, I did put a THIN bead of Permatex around the perimeter, and "Plastigage" under both gears, screwed the plate tight and got .0035" clearance on both gears.

Took it back apart and reassembled minus the Plastigage of course.

I also stuck a 1/4" nut behind the pressure relief spring, like we used to do on all the old used cars that came in to our Plymouth dealership with "tired" engines.

That was back in the '60's when cars had oil pressure gauges.

 

So far the Buick has 60 @ start up, 40 @ a hot idle and 40-50 cruising @ a comfortable 55, and we did the oil pump 5 years ago.

 

Mike in Colorado

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All I know is that the one in the picture needs to be a lot flatter than it is. End clearance is death to oil pressure, and a little clearance is a lot of pressure loss.

 

It wouldn't bother me to sand that on a piece of glass. It isn't very big, and since I don't have a surface plate, that is probably how I would do it. Use a figure-8 motion.

 

The best end clearance for an oil pump is as tight as you can possibly get it, as long as you do not go tighter than the shop manual allows. There will be wear on both ends of the gears, so it is almost impossible to get it too tight by sanding a cover, but always check it! Repeatedly!

 

Getting it tighter would involve sanding or surface grinding the pump body, or new gears. That might be necessary if the shop manual thinks it is still too loose after you flatten the bottom plate. Moderation is the key. Don't go there unless you are absolutely sure. It is tough to put metal back.

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Bloo,

Just to let you know, the picture shown is the part with just a "Kiss" on a belt sander shown to illustrate where the leaks around the perimeter are. The dark spots.

I only had to take the base plate down to where these disappeared, as the plate was not warped, like some are.

Used 60 grit emory, followed by 100, then 120 to finish. I did not want a "mirror" finish and I did not make a gasket from a manila folder, like some do.

Although I did make a manila folder gasket for where the pump bolts to the block.

Just used a THIN bead of #2 Permatex around the base plate perimeter.

According to the Buick forums from quite a while back, this is pretty much a standard fix, and the stated max clearance between the gears and plate is .005"

I got .0035 and called it good. See pressures stated above.

 

Mike in Colorado

Edited by FLYER15015 (see edit history)
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  • 3 weeks later...
On 7/20/2019 at 3:02 PM, edinmass said:

Surface plate, surface grinder, and do NOT put any sealer on that at all. 

 

My recent restoration now has 700 miles on it.  My oil pressure DASH gauge shows about 33 psi at start, and holds that at 60 mph.  I was afraid the pressure was too low, as the dash gauge drops down very low when warm at idle.  I checked the pressure at the BLOCK with a gauge, and I'm getting about 42 psi at start.  So, my dash gauge seems to be off about 10 psi, but also means I'm only getting 10-15 psi at hot idle.  

So....  I purchased another oil pump from Dave Tachney and sent it out to Egge to be professionally rebuilt.  I just got it back and it definitely appears to have a sealer around the perimeter of the plate.  Do I have to worry about the sealer?  Will it dissolve out or something?

I appreciate your input before I drop the pan and make the switch.

Thank you!

 

 

2104525836_ScreenShot2019-07-27at1_42_13PM.thumb.png.b34dc6b2624b9f643f9002283c9a3a4f.png

At 55 - 60 mph my DASH gauge shows about 33 psi oil pressure.  

The Buick specs call for 45 psi at speed.

 

 

DSC_0152.thumb.JPG.08fddd3b531ebed9d03c836c410f4179.JPG.1b65c7b64d88d6dcfdbef88be25ad081.JPG

So, I checked at the block and I'm getting 42 psi at start up, so my DASH gauge is off by about 10 psi.

 

 

IMG_5720.thumb.jpg.a728f138707be6362bf6ff4d51646539.jpg

I got the rebuilt oil pump back from EGGE and there is clearly a sealant around the perimeter.

 

 

IMG_5719.thumb.jpg.17bee4532c07259ea4d4b6135290deda.jpg

I'm planning on sanding all that extra sealant off the outside before I install it, but is the use of sealant considered a "no-no"?

Thanks for any information before I drop the pan and install this rebuilt unit.

 

Gary

 

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