Low oil pressure after not running engine for some months.

[John P]

Hi,

My Ulsteroid is fitted with a 1931 2-bearing engine which has been modified but does still retain “spit and hope” lubrication.

I have a 0 – 10 psi oil pressure gauge and usually this goes right around to maximum when the engine is started but then falls back to virtually zero once the engine heats up.

I haven't run the car for probably 3 to 4 months so today I thought I'd at least start it up to let the engine heat up and circulate the oil.

After a bit of tinkering it started OK but the oil pressure gauge didn't move at all. I revved the engine quite hard (just for a few seconds) and the gauge does move but only up to say 5 psi and drops back to zero immediately you return to anywhere near tick-over. I was worried because, being cold today, I'd have expected the pressure to stay high for some minutes.

I didn't leave it running for fear there was a problem and I didn't want to do any damage.

Any thoughts?
John.

[GrahamW]

i would check the pressure relief valve.
The ball might be stuck.

[Charles P]

Relief valve or a sump full of water

C

[Howard Wright]

Hi John

Check for leaks on the oil pressure pipe work.

Cheers

Howard

[Peter Naulls]

Could there be an air lock in the pressure gauge pipe? I can't imagine the pressure relief valve would stick in the open position.

[andrew34ruby]

Could there be an air lock in the pressure gauge pipe? 

No. It measures pressure, no-matter whether it is oil or air.

[John P]

Thanks for the suggestions.

I take it that for the pressure to be low the ball in the pressure relief would have to be held off it's seat or the spring has broken.

I'll try taking it out once the weather warms up a little but what's the best way to check and clean the seating.   (I'm assuming it won't be easy to see, especially with the engine in the car).   Do you think liberally squirting WD40 into the hole after removing the spring and ball would help achieve this?

I suppose it would also be sensible to get a new spring and ball anyway.

John.

[stuartu]

You might be surprised by how little is needed to stop the PRV ball seating.
If there is no water in the sump and no other obvious culprit you may wish to remove the PRV. In my experience you will need to jack up the rear of the engine a bit to do this, obviously ensuring that you won't damage something else in the process. It's tedious. You will have to disconnect things.
If you get the spring and ball out, examine the ball carefully. I would tend to replace it with a perfect clean example because that's easier.
To flush the seating, I would put a clean tray in the appropriate place and rotate the engine to flush outward from within with its own oil, then examine the entrails in your clean tray.

Hope this helps.

Stuart

[Chris KC]

I'd certainly urge you to stop and find the trouble before driving the car again. The only time I ever lost oil pressure (in Newhaven, on the way to the ferry for a quickly-aborted holiday - and the only time my car came home on a trailer) a subsequent strip-down found a flake of ancient red hermetite lodged in the oilway. It was blocking the oil pressure gauge take-off in fact, but might easily have migrated to a point where consequences could have been more severe.

With the engine in situ you should be able to check for water in the sump (just crack the drain plug open, water will sink to the lowest point) and may be able to check the PRV / oil pump (with sump off) - depending on your car and your agility. From there it would be engine out I think.

[Ivor Hawkins]

Please don’t take this comment as being “ preachy” John, but I have found problems like this occur if the car isn’t used regularly, even just a ten mile tootle once a week keeps everything working well!