The V8 Owners Forum -

I have a 3.5l rover v8 running in my Toyota Hilux. When it is first started everything is fine, but once the engine warms up the oil pressure light comes on. My question is….Why does this happen and how do I fix it?? Any help is greatly appreciated.

Hi,
I would check the oil pressure with a gauge to see where it is both hot and cold!

Rover V8's are reowned for their low oil pressure, would guess pressure is dropping as the oil heats up and viscosity changes.

Is it running on the correct grade of oil?, modern semi-synthetic/synthetic grades can lower oil pressure

It could also be due to wear in the bearings, do you know the status of your engine? just rebuilt/2nd hand unit/history unknown?

Hope the info helps

Make sure your using 20/50 oil.

What is the mileage on the engine?

As for the milage of the engine....not sure, with it not being the original engine it's difficult to tell.

I overhauled the top end but left the bottom end alone so not sure about the condition of the bearings.

At the moment it has semi synthetic 10w-40 oil in. Will that make a big difference?

Where is the best place to get an oil pressure gauge from?

10w/40 is way too thin for the rv8 mate,
use at least 20w/50

i use fully synthetic 20w/50 in my 3.9

thev8kid wrote:10w/40 is way too thin for the rv8 mate,
use at least 20w/50

i use fully synthetic 20w/50 in my 3.9

Ill go with that

Do you mean the oil light comes on at idle?, or all the time?

Chris.

The light is on once the engine warms up at all rev ranges. I'll change the filter and put the correct oil in this weekend and let you all know what happens. Cheers

JimMet wrote:The light is on once the engine warms up at all rev ranges. I'll change the filter and put the correct oil in this weekend and let you all know what happens. Cheers

If its on all the time I would say you probably have a problem with the pressure relief valve sticking when the engines hot. Change the oil anyway and see what happens, if it still does it then hit the oil pump body with a rubber mallet and see if it sorts the problem. If it does your valve is sticking and you can replace it with the better designed tadpole valve. See old forum for description of this type of valve. Course you could also simply have a bad pressure sensor.

I put 20/50 oil in but the oil light still comes on.

I tried hitting the pump to see if it would release the potentially sticking valve but it had no effect.

Would it be worth replacing the valve with a tadpole one just to see if it has an effect?? If so where is a good place to get one from and how easy is it to fit?

only one place i know of sells them and that's JE engineering. you could take the pump base off and see if he valve is stuck.

Hi ,
Are you sure that it's not a faulty oil pressure switch. It would be unusual for the light to be off when cold and then on when warm, even when revved.
Are the tappets noisy when the light is on ?
Jim

I'll take the pump base off like katanaman said and see if the valve is stuck.

The tappets make no noise at all.

if the tappets aren't making any noise then try Jim's suggestion first.

Sorry to need to be spoon fed on this one but......

Is the oil pressure switch the thin piece with 3 spade connectors on the end that comes out of the oil pump casing or is it the shallow cylinder that's about 2 inches in diameter and about 1 inch deep?

Neither have wires going to them.

When it comes to replacing the oil pressure switch is it as simple as screwing the old one out and replacing with the new?