MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Oil Pressure Warning Light

I am about to fit a T adapter and pressure switch to our V8.

I have tried the fitting and it fits onto on the MGB pipe joiner piece in the photo so I assume it is 1/8 BSP?

I think I will have to go for an adjustable switch as at 20 Psi it might be coming on all of the time when idling. I have seen all sorts of idling pressure quoted so I will have to set it so suit our car? 5 psi, the only other fixed one I can find is far too low.

This of course does not give you much time if it does go when you are pressing on - we will hopefully be doing a few special tests in it later in the year so some clear visual alert is handy. Been there got that T shirt.......

It will be lower than 20 PSI idling after the tests but I can accept it coming on then, it will soon return to normal when we move off. I am really looking at failure when driving but not coming on all the time when idling in normal use.

Any thoughts and have I got the correct thread size?


Mike Dixon

The switch thread is 1/8" NPT from what I found, the thread angles are different to 1/8 BSP.

What are you using as a Tee? I managed to get a couple of the North American adapters which include a Tee for the switch that controls the anti-runon valve, but also found the wherewithal to modify a standard connector to take a switch.

I can get down to about 10psi hot idling although I have the idle speed set so that it doesn't drop below that when the fans are running - it can otherwise. Roger Parker with experience of Police Range Rovers left idling for long periods has said "What hot idle pressure?" i.e. it can drop off the gauge altogether. I used 20psi on the roadster as it never idles that low so should give an early warning or pressure failure, but standard switches are usually in the order of 5-6psi so that is what I used for the V8 as I don't want it glowing at me stuck in traffic. Given the rise time of the gauge it also goes off sooner so I know pressure is there before the gauge starts moving.
paulh4

I am fitting it to the oil filter housing where my oil pressure pipe comes out. I have few other options really as the pressure feed pipe is plastic - see photo.

I assume I need 1/8 BSP to go into the oil filter housing, same on the male end with a 1/8 NPT in the body of the T for the switch ?


Thanks for the heads up on the pressure - I think I will give a 5 psi fixed a go - too many flashing lights stuck in traffic is annoying. Good idea on the idling speed as well, I quite like a faster idling speed anyway


Mike Dixon

Ah, the early arrangement ... it came direct off the pump later on to improve gauge response!

I don't know but would have thought the threads would be the same otherwise one could screw the male-male adapter in the wrong way round.




paulh4

I thought I had some info somewhere regarding the tee for the V8. That says the hose I had made up by Stevson Motors had 1/8 BSP cone fittings for the roadster connector and the adapter in the oil pump (in my case). The cone seats in the connector can clearly be seen here https://rimmerbros.com/Item--i-AAA628, and there are unused threads visible on the pipe side of the adapter in your picture of the filter and of the roadster connector. This type of fitting has no sealing washers.

However the adapter screws flush into your filter housing (and my oil pump) with a copper sealing washer i.e. no cone seat and no unused threads.

The two ends of the roadster adapter 11G15 are completely different and can't be confused as here https://mgaguru.com/mgtech/parts/11G/11G15.htm, but I can't be sure that is the same for the V8 as it doesn't seem to be listed in the Parts Catalogue.

If that wasn't enough the fitting at the gauge end of the pipe also has unused threads, but that uses a flat seat with a sealing washer!
paulh4

Thanks I have speculatively ordered a T and 5 PSI switch - I will report back!
Mike Dixon

This thread was discussed between 22/04/2025 and 24/04/2025

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now