oil psi

[Robert Thornton]

My oil psi is 40psi when cold after 30-40 mi it drops to 30 psi at speed and 5 to 0 psi at idle pull throttle out for faster idle picks up a little. does not smoke or use any oil, just seeps at front and rear seal. would it help to clean or replace oil pump. If screen were plugged it would stay low all the time. how hard is it to replace oil pump. motor only had one valve job in its life. also there is no loss of power, smoke ,or noise. it really runs good. I have had old Farmall tractor 4 cylinders ran for 20 years and worked hard with out any trouble. Any picks on changing oil pump Thanks Robert              p s just gave 53 motor with 60 psi to friend on forum I just wonted to keep matching motor.#

[TodFitch]

Your oil pressure is not extraordinarily low. For 1933 (first year for that basic engine) there is no shut off of flow through the filter if the pressure is too low. Manual simply calls for 30 psi at 30 mph. So you are low but not horribly low.

 

Low oil pressure can be from a number of things:

Obstruction in the oil system (clogged screen, etc.)

Worn oil pump

Faulty oil pressure relief valve

Worn cam bearings

Worn main bearings

etc.

 

Or it may just be that your oil pressure gauge is defective. . .

 

So how do you know it is the oil pump? Are you just going to throw parts at it until it is better?

 

I personally would start with the oil pressure relief valve as I know they can sometimes get sticky or the spring can fail.

[NiftyFifty]

First before you do anything is hook it up to a manual gauge and see what the actual pressure is regardless of the gauge. From there I would say its likely best to just freshen everything rather then throw parts. These engines can run well with lower pressure, but they can also implode out of the blue like my original 218 did in my 50. It ran good, smoked just a tiny bit, but had good pressure until warm... Then about 3 miles from home it decided to drop a rod through the oil pan.

If you want to save the engine, I'd pull it and all new bearings, rebuild or new oil pump and make sure the oil galleries are all clean.

Good luck

[John-T-53]

What weight of oil are you running? Sometimes a thicker oil is the simple solution when engines get a little worn.

 

I'm gonna take a guess that your motor is up there in miles, but doesn't seem like anything to worry about. When the oil heats up, the pressure drops. The bearings are probably just worn a tad, which means the clearances are bigger, not keeping the pressure up there. It is normal for the pressure to drop significantly at idle. I have a motor with 6,000 miles on it, and when hot, the pressure goes down to about 5 psi at idle.

 

The oil pump can wear and cause a pressure drop too; the clearance between the end of the gears and the cover plate is the spot that usually gets affected. The pump is easy to remove and replace - might be worth it just to check clearances. Just mark the location of the gears so you get it back in the right spot. and note the position of the distributor rotor so it doesn't move. The shop manual gives a good how-to on this.

 

Don't push the motor too hard and you should get a lot more use out of it.

[54Illinois]

Is the oil being diluted with gas?

[Robert Thornton]

I use 30 weight none detergent and add one  bottle of stp . I have tried another gage about the same. this is one reason I went with jeep 355 rear end lower rpms. I thought as old and never been out of truck new pump might something you need to do anyway . oil psi plug if spring not broken what else do I look for. truck has been stuck on 86000 for the 15 years I have had it longest trip 150 round trip also truck set up in garage for 30 years before I got it.  as far as I can tell no gas in oil. have a friend that blew off oil pan that had gas in oil.  thanks for your help. robert

Edited April 11, 2014 by Robert Thornton

[NiftyFifty]

If your using a real oil pressure gauge and same psi then I'm going to say your mains are just worn and allowing more bypass. Its not a horrible job, but it is a big one to rebuild, but if you did it, its likely to last you all the years you want to run it. Without its a ticking bomb, because you really should have 7-10lbs per 1000rpm hot and lower rpm lugs the motor to a point and can do worse damage. I know guys will run like this, but one guys luck is another's disaster

[Jerry Roberts]

Your oil pressure relief valve spring could be weak too , after all , it sat in the garage for 30 years after who knows how many miles . You might try a spacer behind it and see what it does . You could stretch it too but once it is stretched , it can't be un-stretched . Probably your engine is worn as others have said . The oil pressure relief valve springs come in different strengths , they are color coded . This is just a patch to make you feel better though .

[Don Coatney]

New replacement oil pressure relief valve springs are available from several sources. When I rebuilt my engine I found the spring broken. With the new spring in place and a "fresh" engine while on a trip 500 miles from home my oil pressure suddenly jumped to over 60# and stayed there. Pulled the plunger and polished it using emery cloth and a drill motor. Reinstalled and oil pressure was back to normal. I read somewhere that shimming the spring is not a good idea.

 

 

 

[John-T-53]

New replacement oil pressure relief valve springs are available from several sources. When I rebuilt my engine I found the spring broken. With the new spring in place and a "fresh" engine while on a trip 500 miles from home my oil pressure suddenly jumped to over 60# and stayed there. Pulled the plunger and polished it using emery cloth and a drill motor. Reinstalled and oil pressure was back to normal. I read somewhere that shimming the spring is not a good idea.

 

Is the 2" long spring a new one? Where to get?

Never though of replacing it!

[Don Coatney]

Is the 2" long spring a new one? Where to get?

Never though of replacing it!

I don't recall where I bought it but many of the old car/truck vendors have them.

[_shel_ny]

Is the 2" long spring a new one? Where to get?

Never though of replacing it!

Don's DeSoto engine spring may be different than needed for some other vehicles. Plym/Dodge 218/230 do not use the same spring as the Soto

[Robert Thornton]

The spring is less than 2 in long has to flat spots on it can not get plunger out any one have a good trick. Or do you have to remove oil pan.

[Don Coatney]

The spring is less than 2 in long has to flat spots on it can not get plunger out any one have a good trick. Or do you have to remove oil pan.

I used one of these easy outs. Removing the oil pan will not give access to the back of the plunger. Use a good solvent that will loosen the shellac.

 

 

[Charles Furman]

Great info Don.

[Robert Thornton]

Thanks Don just what I needed to know as always you information is priceless we rely on you a lot  I hate I did not get to meet you before you had to move we just lived less than 150 miles apart and I am in the Murfreesboro a lot dealing with my disabled Vietnam vet brother should have made the time..Thanks again Robert

[_shel_ny]

The spring is less than 2 in long has to flat spots on it can not get plunger out any one have a good trick. Or do you have to remove oil pan.

 

If you have a 218 or 230, the spring will likely be 1 7/8"

 

Previous threads.

 

No resolution, but some info.

http://p15-d24.com/topic/34385-218-engine-frowny-sounds/?hl=%20removing%20%20plunger

 

Nother, resolved

 

http://p15-d24.com/topic/34201-oil-pressure-at-idle-65psi/?hl=%2Bremoving+%2Bplunger#entry345582

 

EDIT:  to add to what Don has provided please note that his diagram is for the full flow filter. Bypass varies slightly. One thing is with the plunger/valve? No hole through the face of the plunger/valve for oil to travel through to the filter.  (Bypass diagram attached)

Edited April 15, 2014 by shel_ny