Oil pressure

[davie489]

Hi
Any ideas?
Been using the car everyday this week and alls seems fine with good oil pressure at constant 30-35psi which seems to be the norm . But today and probably one out of 5 times I drive it oil pressure goes to zero after 40 mins of driving and returns back to normal later on drive or next day it's fine.

Regards
Dave

[john.p.clegg]

It could be the oil pressure,but I doubt it,it could be a faulty connection between the sender and gauge/supply or it could even be harmonic interaction between the sender and the voltage stabiliser ( both are bi-metallic strips vibrating ).
First port of call is to jiggle all your wires while watching the gauge,bearing in mind it is dampened,so any movement is slow....

Good hunting

John

[davie489]

Thanks John

I will look into this ....
A new pattern seems to be happening now . When driving with high revs oil pressure is fine but when dropping down the revs around town the pressure drops to zero.
New to classic cars..... I absolutely love the thing but it does drive me nuts .

Dave

[john.p.clegg]

With your latest diagnosis,I would check the oil pump,maybe the release valve,try fitting an oil pressure gauge in place of the sender...

John

[davie489]

Thanks for the advise John

[theelanman]

I go with something electrical too.......even something as simple as a loose connection on the sender.....
if it disappears for a moment but then comes back....its not the pressure that's dropping

[rgh0]

If the oil pressure is really dropping to zero you should be hearing the bearing( death) rattle. If the engine sounds normal then its most likely a gauge problem

cheers
Rohan

[davie489]

Hi Rohan
The death rattle? What does this sound like? theres rattling noises when driving but think just general car noises . They come from dash area
Thanks
Dave

[rgh0]

When the oil pressure drops to zero truly, then you will hear a heavy knocking rattle from the big ends. At low revs you can hear the individual knocks at high revs ( say 8000rpm) its more of a continuous load rumble.

Its very different noise from most rattles and knocks and is proportional to engine speed

cheers
Rohan

[el-saturn]

...................as the gauge needs actual physical pressure, i'd also look for a leak somewheres! (see floor) sandy

[davie489]

Hi sandy

I do have a leak from the rear crank seal which I know is an engine out job and want avoid for a while and it's very minor .
Could this cause the zero oil pressure?

Regards
Dave

[davie489]

Hi sandy

I do have a leak from the rear crank seal which I know is an engine out job and want avoid for a while and it's very minor .
Could this cause the zero oil pressure?

Regards
Dave

[tvacc]

That is why I have never liked electrical gauges. I do have one on my Caterham, and do not like it at all. Anyways I also vote for an electrical fault unless you hear a "difference" in the motor sound when it drops to zero. I would remove the bonnet and try to get it to do it while the bonnet is off to hear it better. There will be a rather noisy difference with and without oil pressure.

This is a low pressure high volume system. and looking at the above question, no, a bad seal would not cause low oil pressure.

The cost of oil pumps is rather low. Much less than blowing motor. You might want to replace it just to be sure.

[Galwaylotus]

If you had zero pressure you would know what the death rattle sounds like. It isn't subtle! Check to make sure you dipstick is accurate too. Mine is set too low so it appears to be full when it's actually not. I found that out on roundabouts! I changed the oil and carefully measured the correct amount then checked the dipstick and found it was much higher than the FULL mark. Lesson learned.

[Hawksfield]

Dave

If its electrical gauge you will have a transmitter next to the dizzy, these can fail at different pressures and give false readings. I don't think these a now available or weren't when I had problems some years ago.
My solution was to cut the canister around its circumference then clean the contacts carefully and re solder the canister again. this takes some care but is possible, mine has now been fine for around 15 years