High Oil Pressure

[alanrichey]

Some months ago I fitted a cheap Chinese electric oil pressure gauge to my Superspec.  Initially I was a bit concerned as when the engine started it shot up to 90psi and under load went to 100 psi.  Even when the engine was warm it still hovered around the 90psi mark when cruising and dropped to only 80psi when idling.    

The official pressures from the Rover T16 manual are 0.7 bar (10.5 psi) for the idle and 3.8 bar (57 psi) when running.

I just decided there must be a mismatch between the sender and the gauge so ignored it, although I was glad of it when I holed the sump as, unlike the warning light, it gave plenty of warning that I was losing oil.

Anyway, I decided to treat myself to a proper, old school, mechanical one and see what that read.   Fitted it all in and started the engine.   Slightly better, but still very high.  At idle the pressure was 70psi, rising to 80 psi when I blipped the throttle.  So took her for a run to warm the engine up and when I got back the 'running' pressure was 76 psi and the idle was 62 psi.   So still way above specification and I am not sure what to do, if anything.   Maybe those are minimum values and the engine is just very healthy?  

Any thoughts ?

 

 

[richyb66]

Pressure relief valve sticking? It's easy to get to and inspect. Might be worth just replacing it, the parts aren't expensive. 

[alanrichey]

Not sure that is true of the Rover T16.  The relief valve is inside the oil pump and to access it you need to remove the timing belt and tensioner and then remove the oil pump itself.    Not my idea of 'easy'

And that would not explain the high idle pressure would it ?   I can't actually find anywhere what the relief valve is rated at, although 80psi sticks in my mind from somewhere.

[richyb66]

I thought the prv was fitted externally to the front cover. The pump is inside the cover concentric to the crank. 

If the valve sticks it will over pressure. I had the valve stick on my pinto and it blew the oil seal out between the filter and the block. 

The pressure rating might be on Rave. 

Edited April 23, 2019 by richyb66
Picture added

[geordie40]

Hi Alan

Just checked mine and its about 60-62psi on a cold engine but its on a cheap Chinese gauge (in process of replacing them for etb ones), I know Dean has fitted new etb gauges so maybe worth asking him to check his as well

Edited April 23, 2019 by geordie40

[kevin the chicken]

Does sound like a sticking prv. They get little gritty bits of carbon on them. It can be a bit of a pig to check them on my redtop but  I treat it as part of the annual service even though I replaced the original metal piston with a motorsport spec plastic one at an eye watering 60 quid. Getting it back in against the pressure of the spring is the difficult bit but I have developed a way of doing it which is a bit easier. It may be that yours is the same, clean out and inspect bore for scratches and grit.

[alanrichey]

I'm a bit confused.   Let's suppose the PRV is set at 65 psi, which is just above what the manual says is the normal pressure under load..   So when under load it should keep the pressure at 65 psi.  If it is stuck then that explains why my pressure goes up to 78 psi under load.   But when I idle the engine the pressure drops to only 62 psi and the PRV would not have anything to do with that.  Isn't it more likely a blockage ?  A bit like narrowing of the arteries causes a high diastolic blood pressure.

We also have to bear in mind that most of the Superspec Rover engines idle at 1000 rpm rather than the official 850 rpm, so that would make it a bit higher.

Edited April 23, 2019 by alanrichey

[geordie40]

Just read a post on an old Morgan forum and someine running a T16 engine in their Morgan has a oil pressure of 4-4.5 bar which equates to 58-65 so maybe its ok

[alanrichey]

I assume it's been doing it for the last 22,000 miles so I am not panicking

[blue]

Hi in my tech books I have for the T16 

Oil pressure at idle................................. 1.0 bar(above 80 °C)
Maximum oil pressure at 6500 rev/min........ 7.0 bar(below 40 °C)
Oil pressure warning light switch opens...... 0.3 - 0.5 bar
If this helps 

[alanrichey]

That’s interesting.  If the maximum allowable pressure is 7.0 bar (105 psi) then I guess the Pressure Relief Valve will be set slightly above that, so that takes it out of the equation and makes my 78 psi at 3000 rpm look perfectly acceptable.   But I still need to figure out why it doesn’t drop more at idle.  Although it’s better to be high than low 

[Kerry]

The oil pump will always deliver more fluid on increase of RPM, and will not have any internal regulation, assuming all parts are working ok

The pressure relief vale is the component that regulates the oil pressure, and the stronger the spring the higher the pressure.