VK v8 breathing problem/oil pressure problem

[Bookanun]

Hi all,

I am having problems with the oil pressure in my vk v8. When i start it the oil pressure gauge goes up to flat out and stays there, what would cause this? Is it the gauge maybe? It has a high volume oil pump on it, but i have run them before and they have never sat flat out the whole time. Would it have something to do with rocker cover breathing? Do both rocker covers need to have breathers on them? I currently have 1 small chrome breather on it, is that not enough maybe?

Thanks in advance

[DerekP]

could be the oil pressure switch

[Bookanun]

Ok i will replace that, anything else that could cause it? it has got me stumped! How do you know if your engine is breathing enough?

[RazzaCaine]

my oil pressure in the vb goes to near the top when i first start it for the day and hits the max at around 2500rpm, after about 10 minutes once its warmed up it sits just below the red zone. im assuming its normal as the oil gets thinner as it gets warmer, hence the drop in pressure

[delcowizzid]

is it a procomp high volume pump many of them blow oil filters to bits cause the pressure valve doesnt work

[Darren_L]

how old is the oil pump ?
I'd be checking the pressure relief valve operation in the pump

engine PCV operation won't affect oil pressure, however it will damage the engine & seals if it isn't breathing properly

[Bookanun]

Not sure of age of pump, how do you check that?

Also do both rocker covers need a breather? I currently have one on the D/S front, just a chrome mushroom breather

[VK SL 3800]

One should be fine, the breather is there to release crankcase pressure so you dont have seals being blown out. make sure the breather is not clogged and is working, it would not have any effect on oil pressure however.

[Guzzoline addict]

Is it a mechanical or electric gauge?If it is electric the gauge could be earthing out.

[DerekP]

I still reckon it's your oil pressure switch. Process of elimination, start with the easy stuff first before you pull your engine apart. As VK SL 202 said check your breather valve but still this shouldn't effect oil pressure.

*Edit* I should probably say sender rather than switch since you have an oil pressure gauge rather than a silly light.

[VR38]

I reckon bolt a standard pump back on it.

[Darren_L]

Is it a mechanical or electric gauge?If it is electric the gauge could be earthing out.

good point, if the circuit shorts to ground, the gauge will read max pressure
To the OP, I'd suggest disconnect the sender unit wire from the sender unit and check if the gauge is still reading or drops out. If it still reads, then there is a short in the wiring.
Also as suggested check the sender unit itself. It may also be at fault

[ari666]

why a high volume pump? all they do is pump oil into the rockers and suck the sump dry. unless you have done something to get the oil back in the pan i would be putting a stock pump back on.

nevertheless, the earthed out sender seems like the right idea.

[VK SL 3800]

I have discovered today a weird thing with the oil pressure sender, when the wire to the sensor is left off it goes all the way over to the right, the gauge itself runs three inputs, + 12v a full earth and the variable earth from the sensor, and when left off or unplugged the gauge goes crazy. Took me ages to figure out cause i thought i had a short somewhere then a dodgy gauge, but then i went and unplugged my other Vks oil sensor and it did the same thing, it must require the variable earth to control the movement somehow.

[Bookanun]

thats all good info guys, i have now got a new oil pressure sender and am changing it out tomorrow, hopefully all good!

Thoe oil pressure relief valve was definatly not stuck on so it hopefully is the oil pressure sender. Will pull the wire off to have a look.

Cheers for your help.

[DerekP]

Good luck with it, let us know how you get on.

[Bookanun]

Hi guys, changed the oil pressure sender and presto!! The gauge works like a dream, stoked!! Cheers to everyone for their help