10 replies to this topic

[mk=john]

Hi
I have a 998 Mk1 Cooper, and the engine has done 1400 miles since being reconditioned. It has and is running what I think is high oil pressure.
For example, when I start the engine the pressure is up to 85-90psi (as shon on the gauge) and this takes time to drop to aound 75psi for friving at around 65mph.
However, when the engine is hot, the pressure holds at about 55psi when idling or driving up to 40mph.

Saying that, at idle, the pressure has dropped to below 50psi

I suspect the problem might lie in a sticky or faulty oil pressure releif valve. Has anyone had this problem?
Is the releif valve likely to be the problem or could it be something else?

Thanks

[dklawson]

Your oil pressure doesn't sound like it's doing anything wrong for an engine in good order. If the cold engine pressure seems a bit high to you, consider installing the adjustable relief valve with the ball bearing in place of the plunger. Properly set up, that will keep your cold pressure closer to 50 psi. Your hot oil pressure at idle is what it is. The hot idle pressure isn't usually affected by the relief valve unless it's stuck. The hot idle pressure is usually an indication of the component clearances and the condition of the oil pump.

[mk=john]

Thanks for the reply.
Do you think i should have anything to worry about with the ouil pressure as it is? I worry that I could blow shaft seals etc. As far as I know everything has been reconditioned, and I have done 1400 miles since the rebuild.
In your opinion, what is the best route, 1) look the the relief valve, 2) look at the oil pump, or 3) not worry too much at present?

Bye the way, I am running Halfords Classic motor oil 20W50 especially for classic vehicles.

Thanks

[Jammy]

Nah, that oil pressure is fine. In fact its ideal!

[dklawson]

Sorry, I guess I wasn't clear. I think your oil pressure is fine. I only suggested the adjustable ball bearing relief valve so you could set the cold pressure where YOU want it... if it will make you feel better.

Again, your oil pressure seems great. Enjoy your car.

[Jammy]

Sorry, didn't want to go against anything you said DK, just wanted to reaffirm your point that the oil pressure was fine.

[mk=john]

Thanks for your help guys.
So I am in no danger of blowing oil seals then?

[dklawson]

If by "seals" you are talking about the crankshaft seals... the engine oil pressure has absolutely nothing to do with their performance. They don't seal against the pump, they seal against the build up of air/fume pressure inside the crankcase. Again, there is no direct contact between the high-pressure oil system and the crankshaft seals.

[mk=john]

Thanks for that.
I am still learning lots about my car and when I see what is a potential problem, then I post on here.

One last point, sometimes the oil pressure on starting is up to 95psi (as indicated on gauge), but at hot idle down to 55psi as mentioned.

Basically, from this topic and your replies, I assume that the pressure fluctiations are indicative of an engine in good condition and there is nothing I should be immediately be concerned with.
Right?

Thanks for all your help on this anyway.

John (Proud owner of a Mk1 Morrris cooper!)

[Jammy]

Yea, its all to do with the weights of the oil. When it says 50/20, 40/15, etc on the oil its talking about the viscosity of the oil when cold and at engine operating temperature. I *think* the lower the number the more viscous it is. So when the engine is cold it will have a viscosity of 50 and so be harder to pump around the engine and therefore create high oil pressure, and when its up to operating temperature it will have a viscosity of 20, being a lot easier to pump around and hence the lower oil pressure.

Edit: Sorry if you already knew that it found it very patronising, just thought I'd make sure this was understood.

[dklawson]

For an explanation of multi-grade and single grade oils see:
http://www.answers.c...pic/motor-oil-2