The V8 Owners Forum -

Anyone any ideas why my oil pressure would do this on a cold start?

750rpm 9psi
1000rpm 15psi
1500rpm 30psi
2000rpm 40psi

Once warm, settled on 30 psi at idle. Dropping gradually to 20 psi when hot. On Idle.

Next day, cold start.

750rpm 40 psi.

Dropping gradually to 30 psi when warm, 20 psi when hot. On idle.

The motor is a 4.6 RV8 with old style timing cover and oil pump.

Why would the oil pressure behave so differently on each day?

Relief valve stuck (partially) open on first test?

Had you changed anything?
Example just changed oil and not pre-filledthe filter, on startup it first has th fill the filter.

Just a thought?

Ian

Crap gauge?

scudderfish wrote: ↑

Sat Aug 14, 2021 7:49 am

Crap gauge?

If it's anything like the electric one on the SD1, very likely.

scudderfish wrote: ↑

Sat Aug 14, 2021 7:49 am

Crap gauge?

It's an auto meter capilary gauge. Seems to make sense most of the time.

I think that as I was running straight SAE30 oil, the oil got too hot after some hard starts an the pressure dropped at idle. For some reason this may have also caused the relief valve to stick and give the weird readings the next day. Once it freed up, the pressure readings went back to normal.

I'm changing the oil to 20w50 and I'll see what happens.

This is a 4.6L with the old type timing cover, so it can run a dizzy, so it has the old style oil pump too.

I am also thinking I ought to fit an oil cooler. The air flow isn't great in a Minor!

Wouldn't waste time fitting a cooler, until you know what oil temps you are seeing

And use a proper oil, can't think why anyone would use an old single weight oil this century ?

stevieturbo wrote: ↑

Wed Aug 18, 2021 7:40 am

Wouldn't waste time fitting a cooler, until you know what oil temps you are seeing

And use a proper oil, can't think why anyone would use an old single weight oil this century ?

The SEA30 was just to flush the old cr@p out, I had a drum of it to use up!

I'll stick an oil temp guage in and see whats happening.