oil pressure problem or not?

[Vigil]

At start up it is a 60lbs after warm up i usually run at 40lbs.
When i stop for a light or sign 20 lbs.
I usually never drive my car on the expressways.
The other day i had no choice.
And found a potential problem with my oil pressure.
While running down the expressway it dropped to 20 lbs.
After i pulled off the expressway and stopped for 20 min it seemed to be OK.
Meaning it ran at 40lbs. I did not go on the expressway again so this is normal driving.
I am thinking the oil pressure relief valve may not be working correct.
I would think it should be around 40lbs even on the expressway.
Is this what your running at after running at 60mph down the road?
The bottom end looked good when i replaced the rings.
I did put in new stock rod & main bearings.
I was told they were in stock spec and should be fine.
Any suggestions on what the problem may be?

Thanks for all your time & help,



vigil

[Alec]

Hello Vigil,

it is unlikely that the pressure relief valve is the cause of the problem. 20 psi is low when running at a good cruising speed,
what oil do you use, it should be a 20/50 Multigrade, thinner modern oils are not ideal.
When you changed the crankshaft bearings, I take it the crank itself is in good order?

Alec

[bmcecosse]

That oil pressure is pretty desperately low - but as long as you stay off the 'expressway' it will last a good few miles yet. The oil pump will be worn and general wear/tear in the engine. As above - use 20W50 oil (even 20W60 mif you can find it) and drive the car gently!

[mike.perry]

California was sunny and hot when I was there in June.
Make sure that your cooling system is in perfect condition, don't set the idle speed too slow as that will lower the oil pressure when stationary

[bmcecosse]

It's the running pressure at 20 psi that is the worry!

[Vigil]

The motor is running redline 20-50 oil.
The water temp runs just below normal.
The crank was in spec - on the out side.
The motor runs strong all day long if under 60 mph.
Sorry i for got to put this information in the first message.

Can the oil pump be removed by just removing the pan.
It is a 1275cc from a MG Midget

I think i will replace the oil pressure relief valve first.
They are cheap & should be easy to do.
That will be one less thing to consider.

Thank You for you help.

Vigil

[Alec]

Hello Vigil,

if the pressure runs at 60lbs per square inch at idle, then the relief valve is lifting at that pressure, when the pressure drops it will just stay shut so replacing it will make no difference, i.e the pressure is too low to unseat the valve so changing it will make no difference.

Do you have a workshop manual as I'm fairly sure all A series engines have the oil pump at the end of the camshaft and you need to remove the gearbox to access it?

Alec

[bmcecosse]

As above - it's NOT the relief valve. May be worth checking with another gauge - because 60 psi on start up is a bit low - should be nearer 70. And yes - engine out to get at the oil pump........

[Vigil]

I was afraid that was the case . I just got the motor back in.
I think i will give it a little while before attacking the oil punp.
I want to get the rings to seat before pulling the motor again.

Thanks again for all of your replys.

Vigil

[bmcecosse]

You could of course fit an oil cooler! That would help considerably when driving it 'hard'.

[Vigil]

Where do you mount the cooler?
I have seem them on several cars.
They hang them to the side of the radiator or flat under the car.
None of the locations seemed to get real air flow.
will one fit in the grill before the radiator?
It looks like a 10 row might.
How do you mount it from the sides, bottom or top?
I was wondering if a oil cooler would make any difference too.
I am learning new things every day. Thanks to all of you.

Vigil

[bmcecosse]

Just fit it where you can - mine was out front, but if you want to conceal it - I guess there is space at the side of the rad, and then make a path for cold air to flow to it!

[Vigil]

I am not quite sure what your mean by up front.
Do you have a picture you can send - uniquelittlecars@yahoo.com

thank you

igil

[bmcecosse]

\\\\\try this one

[Vigil]

great picture

Thank You

Vigil

[bmcecosse]

It wasn't taken yesterday....... in fact > 40 years ago.......

[kennatt]

never would have guessed it

[MarkyB]

It wouldn't do any harm to have a look at the pressure relief valve, it's an easy enough thing to check.

[Vigil]

It has never been changed so the spring could have been changed by the heat is what i was hoping.
I am not looking forward to pulling the motor again.
The parts - valve,spring, washer & new cap if needed are all cheap.
It sure would be great if it solved the problem. I am probably not that lucky.
I was thinking oil pump as a second guess and hoping it was not.

Any one know the size socket or wrench in needed to remove the plug/cap to pull the valve & spring?

Thanks again for your suggestions,

Vigil

[bmcecosse]

1" AF I think. It's working fine at 60 psi as the cold start shows. As I suggested before - try a different gauge.....