I have viewed a Daimler 250 V8 and the oil pressure went off the gauge(over 60 psi) when started from cold. When hot it remained at 60 psi when above tickover. At tickover it dropped to 50ish. The vendor had the engine rebuilt a couple of thousand miles ago.
Is this situation acceptable?
Welcome to the forum.
For a Daimler its exceptional my father had one and the gauge would be almost zero on idle. You cold be looking at blown seals if it really is that high, I would try to get a mechanical gauge hooked into the system and see what that returns.
Thanks for your reply.
I doubt it will be possible to try a mechanical gauge.
I have done some research on high oil pressure in other engines and conclude it could be something simple to rectify but also it could be an engine out situation.
I am still considering the deal but will probably look elsewhere.
I know I have purchased more than 15 oil pressure sending units over the past 27 years that I’ve owned the PrtyKty.
As they fail, they read lower and lower. Annoys the hell out of me as I’m anal about all the gauges working properly.
I eventually put in a “T” and a mechanical gauge.
If I put xW30 oil in the crankcase the needle will peg for a few minutes upon start. But if I put xW40 or xW50 in, it will peg for several miles down the road, and I figure that can’t be good.
Don't you just hate those who live in the US for ten years and never bother to learn the language?
I think no one should graduate from grade school without learning either Cherokee, Apache, Ute or Arapaho.
LLoyd July, 2014
First, that does not sound dangerously high to me, especially for an engine with only a couple of thousand miles on it. I certainly would not pull the engine for something like that. Has it been that way ever since the rebuild, or has something changed? Electrical pressure senders are notoriously error prone. About the only thing that can cause too high an oil pressure is the combination of cold weather and a frozen pressure relief valve. Unfortunately, the relief valve is part of the oil pump. Is it possible to drop the sump without removing the engine?
Thanks Lloyd for your comment.
James you don’t have to worry about seals they are not on the pressurized circuit. But something does need to be fixed so ask for a lower price.
Or keep looking. Tom
Thanks Mike, as far as I am aware the oil pressure has been the same since the engine rebuild.
I do not think the sump can be dropped to access the oil pump without removing the engine.
Thanks Tom, the vendor does not think the high oil pressure is a problem so he will not move on the price.
I am looking elsewhere.
No one has actually answered your question: YES.
Jaguar indicated 10 psi/1000 rpm as normal: a steady pressure above 50 psi at normal cruising will result in oil being heated beyond what it should be
I’d check/adjust the relief valve.
Thanks Paul, does the 10psi per 1000 rpm guide apply to both the Jaguar straight 6 and the Daimler V8?
Whoops! I need to read more carefully!
Not sure if the same applies to the V8: another to make sure of, is if your gauge is showing true pressure.
Is it mechanical or electric?
Thanks Robin, for the information.
This is a gear pump, so if it were totally restricted, the pressure would rise to whatever pressure it took for the housing to rupture or until the drive mechanism failed. The reading on your gauge is a measure of the frictional losses across the bearings and their journals, up to the maximum allowed by the pressure relief valve on the oil pump.
Thanks Paul, it is an electical gauge so the accuracy is questionable. I do not think I will be able to connect a mechanical guage (until I have bought the vehicle). I have found, from another website, that the ideal oil pressure, when warm and running, is 35 to 45 psi.
Thanks Mike, for the information.
What viscosity is the oil?
Imagine it was a 20W50 and you could go down to 40 or even 30. It would bring the oil pressure way down with no harm to the engine, although always subject to religious debate. Many say more flow means more cooling, the thinner the better (within limits).
Modern cars have better tolerances and may I suggest that this rebuild has close tolerances as well. Maybe you can ask the seller what the oil is, and adjust the pressure with the oil thickness in the future.
Any mistakes in rebuilding besides the relief that raise the oil pressure? What is unacceptable?
The valve is hard to get at and I doubt it malfunctions provided that the true pressure doesn’t go through the roof with a very cold start. Oil is cheap and easy.
A stuck or strong relief valve would not show such high pressures at hot idle - a tight, new engine will and a malfunctioning gauge might.
With 50 psi at hot idle I’d start by using thinner oil and see what happens. I always thought 10/1000 was a minimum requirement; an ‘all is fine’.
My father had a Daimler-Jag and it idled at a tad above zero and ran at about 25-30 hot, probably just the sender being lazy. Never had a problem with it.
Thanks David, for the information.