11 replies to this topic

[Monkeh]

Hi, i am getting confused with my oil pressure readings. Cold idle is about 50psi, warm idle is a bit less.

But the thing im confused about is why if i rev the engine the pressure drops, shouldnt it increase not drop???? at 3000rpm warm its 25 - 30 psi.

please help.

[Sprocket]

I suspect a blockage, the brick gaurd in the sump of the gearbox looking favourite. This is causing the oil pump to cavitate.

How old is the gearbox and are you using a center oil pick up?

[Big_Adam]

Drops?

Ooow, err. Thats a bit odd, El Gordo would drop a pound or two of pressure but that was it. From cold to warm then the oil pressure does drop. Past that it sounds odd, maybe the pump. Not too sure though.

How many miles on the clock?

[Monkeh]

i have no idea whats been done to the engine, it was an autocrosser so i suspect it does have a centre oil pickup, so no idea of mileage either, could it be something to do with the relief valve??

[Sprocket]

No, This is nothing to do with the relief valve, its pump cavitation. if the sump strainer is clogged, (the central oil pick ups do not have much area) there is a considerably lower pressure at the oil pump inlet, this prevents the port filling adequately and less oil is pumped. It may be enough to satisfy the engine at idle but at higher RPM its not enough.

Is there a Mag trap at the back of the gearbox?

[Sprocket]

Are you saying that you have no prior knowledge of this engine and what you are witnessing with the oil pressure is as it has always been as you are aware of?

Or

was the oil pressure as it normally should be, and this problem has developed?

[Monkeh]

I dont know, it looks standard from the outside , its one of the later boxes.

[Monkeh]

I cant say really if it did it before or not, i recently flushed and changed the oil to 20w 50. and the car had been stood for a good 4 years.

i recently discovered that the person before me put the rocker pedestals on the wrong way around so that it was blocking the oil feed to the shaft, it might have been after i corrected that that i noticed the oil pressure drop

[Turbo Nick]

we condemned a mates engine a while ago because it was doing the same thing...turned out the numpty hadn't checked the oil level and was on the bottom of the dipstick. I'm guessing you've checked yours?

[Monkeh]

yeh oil level is and has always been good, i spoke to some mechanics at work and they said it could be the pressure relief valve and would be the best place to start. Either its that or i may have to rebuild it and make it turbo

[Sprocket]

Thats some funny physics going on there if it is the fault of the relief valve.

[Monkeh]

do you think it would be ok to drive it with that low oil pressure.