how much Oil pressure do I want?

[dgym]

Hi chaps,
I've never had a car with an oil pressure gauge...when should I worry?

Just got my roadworthy certificate! I'm close to getting legal!

cheers,
jim

[rgh0]

should be between 30 and 40 psi when hot and driving normally. Maybe down to 10 or 15 psi at idle. Depends a little on the oil you use and how worn your bearings and pump are.

Worry if below 25 psi when normal driving or below 10 at idle - or when you hear bearings rattle .

cheers
Rohan

[john.p.clegg]

As ACBC said,it's not about the pressure but the flow...

John

[dgym]

ok thanks gents well I am at just above 10 at idle, and that was worrying me. so ill chill out a little. cheers.

[dgym]

"a little"

[Quart Meg Miles]

Hi chaps,
I've never had a car with an oil pressure gauge...when should I worry?

cheers,
jim

Rohan is right, as usual.

You worry when you don't notice that the oil pressure has vanished and the rattle sounds terminal, as happened to me in my early years when the original plastic pipe fell off the union. I soon fitted a T-piece and flashing warning lamp.

In a recent rebuild I refitted the pipe and switch like this but shimmed the T-piece screwed into the block so that it was tight in the final position (before fitting the switch or distributor). Now it doesn't leak oil but you might find it easier to insert a T somewhere in the pipeline, possibly under the dash out of sight.

[dgym]

when you say a flashing warning lamp do you mean the usual "idiot light" that most cars have? are you splitting the oil send off the engine, so it goes to your gauge and the light?
-Jim

[Quart Meg Miles]

when you say a flashing warning lamp do you mean the usual "idiot light" that most cars have? are you splitting the oil send off the engine, so it goes to your gauge and the light?
-Jim

Yup, I fitted a similar lamp to the handbrake warning lamp, though amber, alongside the oil pressure gauge and built my own flasher. The pipe to the gauge you can see is coming from one end of the splitter and the switch is that disc on the lower end.

I used to have the splitter sticking straight out with the gauge pipe on the end and the switch on the side but it badly dented the heater hose so I rearranged it. Starting from fresh I would attach the pipe as standard and break into it with a custom T piece.

[wgrainge]

Does anyone know: How does a high pressure pump affect pressure at idle? I had assumed that a high pressure pump would cause an increase in pressure at all revs, but ... maybe not?

[john.p.clegg]

I don't know if the plumbing world has a similar equation but in electrics it is V = I x R, where Volts is equal to Current times Resistance....I would expect a similar relationship between Pressure, Flow ,Volume and the available path ( bore of oil galleries clearances of bearing shells etc..etc...)

John

[rgh0]

The normal high pressure pump has a higher relief valve set pressure at 60 psi versus 40 psi in the standard pump but its output volume is the same. With a normal pump the pressure rises from its idle level of around 20 to 25 psi to the relief valve pressure of 40 psi at about 2000 to 3000 rpm at which point it can rise no further. The same thing happens for the high pressure pump but the pressure rises to 60 psi as the engine revs rise in the 3000 to 4000 rpm range at which point the relief valve opens.

If the engine bearings or pump are worn then the pressure may never reach the relief valve opening point even at maximum revs.

cheers
Rohan

[RogerFrench]

Being a bit worried about oil pressure, I fitted a new pump and the reading dropped. I can't get over 30psi cold now.
I do wonder about filter though. When I changed the pump, I changed the filter and I wonder if I got the right kind? I've read lots of archived posts here and ended up as puzzled as I started.
As far as I know, we need a filter with no drain-back valve, no relief or bypass valve, full-flow. What US filter fits that specification, if indeed it is the right specification, please?

[rgh0]

unlikely the filter could cause a 10 psi pressure drop without collapsing. I suspect the relief valve setting in your new pump may be too low and its coming in at 30 psi rather than the intended 40 psi.

cheers
Rohan

[RogerFrench]

Thanks Rohan, that did cross my mind, but I thought I'd explore the simple fix first!

[promotor]

Check that the pressure relief valve isn't jammed open - I've had them stick open with the result being less than 5psi pressure (more likely it was even less as the light comes on at 5psi!).

I've seen it a few times on pumps - it only takes a small spec of dirt to get stuck and it's likely that a piece gets in when the engine is open to the elements when the oil pump is taken off. It's happened to me after a change of oil pump on two occasions now.