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Low oil pressure problems


bosworth

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I finally have my 52 b3b on the road,  tags and all,  have been out joy riding and find that when I go for about 10 miles and the engine is hot, that the oil pressure drops down to about 20 psi.at 40 to 45 mph.  idle pressure is about 10.  When the engine is cold the pressure is up to about 45 psi, idle at about 20.  I don't remember what weight oil is in the engine now,  probably 10w 30 or possibly 15 w 40.  I have a jug of Mobile 1 15w50 that I can put in to see if it helps.  I can't think of a plan B, other than pulling the pan and checking the main and rod bearing wear.   The engine seems to run great, starts easily and  runs quietly. Am I missing something, or is it time to do some major surgery??  The engine seems to be good enough that I don't want to do any damage to it by driving it if the oil pressure is inadequate.  

As always,, thanks for your help

Bill

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Hi, and thanks for the replies,  I don't plan long distance trips, but would like to make it more of my daily driver,  probably 30 miles per trip.  As far as compression, seems to run from 125 psi, to 135 psi,  which I assume is ok.  I don't know about the rpm's at  I have a  350 jeep rear axle and the tires are 235- 75- 15 so their about 29"D.  it seems that the engine is still kind of busy at 55 mph,  but at this stage I have done nothing to the interior, no sound proofing, so things get a little noisey. 

 Trying a second oil pressure gauge is a good idea,  I just may invest in one or I can plumb in the original. 

I know that to make any kind of a decision about bearings, the pan has to come down and a cap or two removed.  Is just changing out the bearing a feasible option,  it seems like a gasket kit an rod and main bearings would be less than $200,  this is not a job that I have done before, hoping my neighbor has though.  Any thoughts?

Bill

Edited by bosworth
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Go for Shell Rotella 25/40. Throw in a quart of Castro High Mileage. Worked for me (so far). 

I don't get the "drop the pan" plan. How are new tie tod bearings going to change oil pressure? What am I missing?

How about hedge your bet with a complete engine overhaul. While the engine is at the shop, scout out a twin carb manifold :)

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38 minutes ago, FlashBuddy said:

don't get the "drop the pan" plan. How are new tie tod bearings going to change oil pressure? What am I missing?

Rod and main bearings have oil holes in them for lubrication. When the bearings wear out, the oil passages get slightly larger and the oil pressure drops.

Low oil pressure is a good indicator your bearings are getting thin.

 

And for that reason alone, if I had a good running engine, I might spend a weekend dropping the pan and checking the bearings. Before one goes out and scores the crank and causes more damage.

Of course I would want to exhaust all other avenues of repair first .... like asking on the p15-d-24 forum  :D

Edited by Los_Control
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2 hours ago, Los_Control said:

Rod and main bearings have oil holes in them for lubrication. When the bearings wear out, the oil passages get slightly larger and the oil pressure drops.

Low oil pressure is a good indicator your bearings are getting thin.

 

And for that reason alone, if I had a good running engine, I might spend a weekend dropping the pan and checking the bearings. Before one goes out and scores the crank and causes more damage.

Of course I would want to exhaust all other avenues of repair first .... like asking on the p15-d-24 forum  :D

little off in the above statement,  the wearing of the bearing as you later states thins, BUT, bearing showing wear the holes do not enlarge, the metal is worn so that the clearance between the bearing and crank is greater and thus has less resistance to flow and there a decrease in oil pressure

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3 hours ago, FlashBuddy said:

Go for Shell Rotella 25/40. Throw in a quart of Castro High Mileage. Worked for me (so far). 

I don't get the "drop the pan" plan. How are new tie tod bearings going to change oil pressure? What am I missing?

How about hedge your bet with a complete engine overhaul. While the engine is at the shop, scout out a twin carb manifold :)

I don't think tie rod bearings are what he was referring to (unless he corrected a typo before I read his post).  He was referring to the main and rod bearings in the engine, which would make a lot more sense than replacing tie rod bearings for an engine oil pressure problem.  :-)

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