Oil pressure

[iain.hamlton]

What oil pressure is acceptable at idle with the engine hot? My idle is about 600rpm at the moment and the pressure reads about 15psi, but over 30 for higher revs. Is this OK?

best regards, iain

[MintSprint]

Yes, it's acceptable. Both sound a little on the low side of normal, but nothing to worry about immediately.

'Standard' pressure is 38 psi at revs, but don't worry about a few psi above or below that.

Idle psi can drop as low as 10-12 with the oil hot before you have to start thinking about a bank raid to pay for the rebuild.

[richardcox_lotus]

It also depends upon which oil you are running. The values for Dino oil are about 40 with revs, about 20 at idle, but I have heard of Mobil 1 Users experiencing < 10 @ Idle when the engine is warm.

[john.p.clegg]

And it also depends on the accuracy of your sender and gauge(how old are they?),might be worth dropping a mechanical guage in the sender hole for a test....

John

[Hamish Coutts]

At the Silverstone classic last year I bought a new standard oil pump at the QED stand. When I fitted it, it produced a slightly lower oil pressure than the old pump I took off and I think that was standard as well!

However, with an engine about 3,000 miles since last rebuild and running good old Duckhams Q 20/50 I get about the same readings as Iain and my idle is set at about 950 revs (I like to make sure oil and water are curculating well in traffic).

Regards,

Hamish.

[Robbie693]

Mine gives around 18psi at idle and just above 30 at speed. I was concerned about this before I bought the car and rang Paul Matty for some advice.

Roger told me that some oil pumps seem to have a lower relief valve setting for some reason and my apparently slightly low reading was probably beacause of this...

[Allison]

Those who have followed our traveldwill know we're paranoid about oi pressure! having done over 5,000 kms in the heat and dust of India I can tell you that your pressures look A-OK. In the S/E engine with Duckhams 20/50 we start cold at about 60 psi but that falls to about 40 very soon. When the engine is hot we don't get to 40 psi again till we're doing something like 55mph in top. Idling in heat has been as low as 5psi but it has always recovered.

Our other car (the engine that did the Dakar rally) runs at the same 40 but at about 30 mph and idles at around 15 to 20 psi.

Conclusion - there's a huge range but so long as it always gets back to about 40 and can maintain that level at constant revs - its ok and vyou have no problems!

Peter

[sparkey]

I'd be very wary of any readings on the electrical gauge in the car. I was at the point of getting my engine rebuilt as the pressure was regularly falling below 20PSI at high revs (I changed the sender to check that it wasn't that) Luckily I got a local garage to rig up a mechanical gauge, which showed very healthy pressure. I now have a proper mechanical gauge which sits just below the dash on the RHS, where I can glance at it for peace of mind, and I also have the original random value gauge. At high revs my engine is at a contant 56PSI, which sounds high, but it's very consistant and has been like this for years so I'm quite happy with it. Doesn't even drop by more than 1 or 2 PSI during track days. At idle its at 15-20PSI. The orginal gauge never reads over 30 PSI and the reaction time of the gauge is so slow it's practically useless.

S..

[iain.hamlton]

The plot thickens.

I went for blast (sorry run) yesterday, and everything was fine. Oil pressure was about 40 with from about 2000 rpm even when hot. When I came back, I left the car idling for a few minutes. The pressure went down to 15 as before, then lower, and eventually to close to zero. I stopped the engine straight away. Left it to let the oil to cool before putting it away later. This morning, i spoke to Burton Power. They suggested that it was probably a sticking relief valve in the pump. As running without oil pressure is is not the kind of excitement i enjoy, I ordered a new pump.

I have seen a number of previous postings about fitting a new oil pump with the engine in (+2). I understand the physical part is a case of dropping the engine slightly, which I assume means supporting the engine, and removing bolts from the RH engine mounting. But there is also a lot about priming the pump. Is it possible to do this by turning the engine on the starter with the plugs out, or is there a way of turning the pump by hand?

best regards, iain

[Hamish Coutts]

Iain,

Because you have already been running the engine, there will be plenty of oil in the engine galleries, so priming should not be a problem.

It would, in my opinion, be far better to prime the new oil pump BEFORE fitting it to the engine (you should also fill the oil filter before fitting it to the pump). This will make sure that as little air as possible passes through the oil galleries.
Yes, you are very wise to turn the engine over without plugs to get oil pressure before starting up in earnest.

Best of luck,

Hamish.

PS Don't be surprised if you get slightly LOWER oil pressure with a new pump as I did when I fitted a new one from QED. The assumption is that the relief valve has a slightly setting.

[iain.hamlton]

Thanks for that Hamish

I am expecting more pressure because i ordered a 65psi pump. May not be wise: it may leak more, but I figure i wont notice a bit more oil on the garage floor.

best regards, iain

[iain.hamlton]

Well, fitted the new pump:
50psi cold
50psi hot 2k rpm +
18-25 psi idling hot.

presumably it wont make the full 65 psi because of some wear in the bearings. Anyway, it's the result i want: always more the nothing!

best regards, iain