Caterham K series erratic oil pressure

[Sumpplug]

Hoping some wise heads can point me in the right direction. Recently bought a Caterham R300 with 1.8 K series. Oil pressure intermittently fell to zero on the test drive but the owner said it was the sender and he had a new one but hadn't fitted it yet. He gave me the sender which I fitted but when the engine is warm the oil pressure still read zero below about 1500RPM. Assumed it was the gauge and ordered a new one from Caterham but no difference. Convinced I was facing imminent engine failure I bought a test kit with a mechanical gauge. With this connected the pressure is 60PSI cold and 50PSI warmed up at idle and no fluctuations. So: its not the engine, the sender or the gauge, what on earth else could it be?

[BertBert]

It's not impossible that the new sender also isn't working well at all. That setup is notoriously unreliable. Probably two choices:

1 ignore it, they all do that sir. You know the OP is fine.
2 upgrade permanently to a mechanical sender and gauge
3 upgrade to the remote sender kit. It removes the vibration which is vaunted to kill the senders.

Oh that's three options. There is no fourth option. Our chief weapon is surprise, suprise and fear, surprise, fear, ruthless efficiency and an almost fanatical devotion to the pope. https://montycasinos.com/montypython/scripts/spani...

Sorry got distracted.

[DCL]

It's likely that the pressure fluctuations are still there, just that the mechanical gauge is dampening them out. What causes them? I think there are many things that contribute to them and my experience is that some engine show it more than others. It could be - engine/oil pump speed fluctuating, worn cams bearings, trapped air, etc etc. But if the mechanical gauge is steady at a good pressure I would not be too worried.

Edit, actually having read your post again, it may be worth running a new wire to the electric gauge and check the earth at both sender and gauge, and the supply which may come from the tacho or speedo (I can't recall which).

Edited by DCL on Thursday 17th June 15:40

[Sumpplug]

Thanks both for suggestions, I'll check the common earth first which I think is under the scuttle somewhere if not that I'll try a new sender, then bin the lot and fit a mechanical gauge!

[PiersR]

I also have an R300K and over the years have fitted four new senders. In reality, I should have fitted a mechanical gauge.

I would check and clean the earths, in fact all earths are worth cleaning.

Piers

[Sumpplug]

Thanks, I tried tracing the earth from the gauge but it disappears into the loom. Having spent 10 minutes stuck in the birthing position with my head in the footwell and my legs over the roll bar I gave up. I'll try running a new earth to the gauge from a suitable place under the dash and if that doesn't work I think I'll follow the consensus and convert to a mechanical gauge

[BertBert]

to be fair, once I had fitted the remote OP sender kit, it didn't break again.

[Sumpplug]

Following my original post I am now in a position to give the definitive answer on how to solve the problem which is as follows.
1. Change pressure sender for one supplied with car, realise this hasn't solved the problem.
2. Replace oil pressure gauge £105 from Caterham. Realise this hasn't solved the problem.
3. Discover replacement sender is leaking oil. Overtighten until the thread strips. Order new oil pressure sender £93 from Caterham
4. Overtighten new sender until oil filter casing shatters into two pieces and oil drains all over garage floor. Realise you have made things worse.
5. Purchase new oil pressure adapter £36.00 from Rimmer Bros.
5. Fit new sender unit and rejoice that unexpectedly you've fixed the low oil pressure reading as the supposedly new sender unit supplied with the car had an identical fault to the original once.
6. Discover replacement sender is now leaking as you damaged the crush washer by previous over tightening.

I hope this helps anyone with the same problem. You may want to omit some of the steps above and save yourself a load of time and money.

[CanAm]

As you've discovered, replacing the standard senders is not the best or cheapest option in the long run. When my replacement sender failed I went for the mechanical o.p.g. and it's been fine for over 10 years.

[AndrewGP]

I had similar issues on my 1.8k powered 7, so fitted a mechanical OPG. Much better solution and proved very reliable. The only snag was it highlighted the oil pressure drop on hard right hand corners so I ended up fitting a dry sump oil system at a cost of £3k……it would have been much cheaper to leave the old gauge in and live with it

[andy97]

AndrewGP said:

I had similar issues on my 1.8k powered 7, so fitted a mechanical OPG. Much better solution and proved very reliable. The only snag was it highlighted the oil pressure drop on hard right hand corners so I ended up fitting a dry sump oil system at a cost of £3k……it would have been much cheaper to leave the old gauge in and live with it

I have had the same issue, and the same outcome!