Rover V8 Oil Pressure

[v8scimitar]

I'm having some problems with the oil pressure on the Rover V8 in my Scimitar and am unsure what to do to solve the problem.

The oil pressure has always been very high on startup, but the last few times I've used the car it is now also very low once the engine has wamed up.

If I'm not gentle driving when cold the pressure can go off the end of the scale (100psi). but typically I can see 60-75psi when cold. More worryingly is that now when the engine is warm i'm seeing almost no pressure at idle and 20-25psi when driving which is quite a bit lower than it used to be.

I've read a few forums and some seem to think this low pressure is normal, others don't. Some say fit a 'tadpole' modified oil pressure relief valve (which I bought but havn't fitted yet), but others say this modification can wreck the engine.

So now I don't know who to believe, or what to do. And I dont want to drive the car with low pressure if it's going to wreck the engine. I did try changing the oil from the 15w50 I was using to 20w50 but this hasn't helped either.

Any advice would be much appreciated.

[mds automotive]

just a thought are you sure the pressure gauge and sender are working properly .

[GreenV8S]

That's a heck of a lot of pressure when cold. Are you running particularly thick oil? If the pressure relief valve was stuck I'd expect the pressure to vary wildly with temperature but also with revs. It seems most usual for them to stick in the 'fully open' position if they're going to stick, so you end up with almost no oil pressure. Perhaps this is what has happened to you. But before you go down that path, I'd check that the sender is working correctly. Eratic readings varying with temperature seem to be a common symptom of a knackered sender, and that's easily fixed with no scary side effects.

The tadpole pressure relief valve is a sensible upgrade if you have the engine apart. My engine builder used one for mine. It doesn't do any harm to the engine (what a silly idea) it's just tapered so it can't wedge in the housing and get stuck.

[Boosted LS1]

The tadpole is spherical so contact are with the cylinder wall is minimal. This is why it can't stick or jam.

I suspect an electrical fault here.

Boosted.

[v8scimitar]

Its a mechanical capilary gauge, not an electrical one. Although there has always been a very high reading when cold, the very low reading when hot has only happened the last couple of times I used the car.

[Boosted LS1]

v8scimitar said:

Its a mechanical capilary gauge, not an electrical one. Although there has always been a very high reading when cold, the very low reading when hot has only happened the last couple of times I used the car.

The guage should be good then but could you try another one? Maybe even an electrical item as a test. The big swing in pressure is unusual. I used mechanical guages also but guess they're not infallible. Thing is, pressure has always lowered once the oil's warmed up. I once burst an cooler blipping the engine when the oil was cold but I had an uprated spring. You live and learn

Boosted.

[v8 racing]

This is actually quite a common problem!! general it is caused by trying to get too much pressure hence the fitment of high pressure springs etc... i would say you have an oil temp problem mainly which is dropping the pressure when hot, try running an ester based oil such as motul/silkoline to aid the hot temps and fit an oil cooler.