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MG MGB Technical - Optimist or Pessimist?

Did about three jobs involving the oil cooler and gauge hoses and fittings yesterday. Did a plugs-out cranking test initially to check for no leaks, then a short engine run, before I got the car out of the garage to avoid it filling up with fuses which then get into the house, for an extended test. Immediately spotted oil spurting out of one of the cooler hoses! Managed to get it back in the garage without getting oil on the drive. The pessimist would say if he hadn't fiddled with the hoses he wouldn't have had the leak. The optimist says if it hadn't happened then it would have happened on the road, with far worse potential consequences. The irony is that the work on the gauge hose and fittings involved fitting a new (Teflon with S/S braiding) hose and a switch for a 'low oil pressure' warning, as there have been a number of hose failures (mine were all original and 45 years old when I started) and other sources of loss of pressure recently. With soon to be three brand-new hoses I probably won't need the warning ... unless with three new hoses at least one of them is bound to fail a lot sooner than 45 years. Or is that pessimistic?
Paul Hunt

Paul, Be very pessimistic with regards to a supplied part made of rubber. I have often wondered whether to keep the end fittings and supply my own rubber hoses. Haven't done it yet though!
Hope you managed to clear up all those pesky "fuses" before they invaded the house!!
Like the idea of the low pressure switch but would have to have a low trip point for a V8.
Allan Reeling

You are an optimist.. You anticipated and prepared for an impending inherent issue that all these old cars will endure.
A pessimist would ignore the inherent issue and have the car fail at a time when the car is not conveniently located. In your case (and mine also) this issue happened at home and further, did not created a larger problems while at home.

79 MGB
gary hansen

Paul - I think that this situation comes under the heading of "no good deed goes unpunished". Cheers - Dave
D W DuBois

Lucky Paul
I think you should go get yourself a Lotto ticket while your luck's in
If that happened to me it would be in peak hour traffic on a single lane bridge with a police car and an ambulance behind me, It would be pouring with rain and the battery would be flat in my phone and the door handle would come off in my hand and---
Not Lucky Paul though -- At home,-I'll just pop it back inside
Cheers willy
William Revit

Fuses - ha! It's the electrician in me, I meant fumes of course.

I'm using a 7lb switch as I want to be aware of sudden and total loss, I'd hope to spot a lesser reduction on the gauge. There are 20lb switches around although I've seen even the roadster get that low when stuck in creeping traffic on a hot day, and I object to paying four-times the price. 7lb might just be enough for the the V8 in 'normal' conditions.

Incidentally Dave Dubois gets my grateful thanks for help in obtaining the very rare North American oil gauge connector that has the port for an oil switch.
Paul Hunt

Optimist !
I had a new gauge hose fail and deposit most of the oil on the road, in the engine bay and on the underside.
Modern hoses are poor.
Richard Thompson


In moving or disturbing the cooler hoses, the minor stresses incurred revealed weaknesses that would not have been present in healthy hoses. So, I'd say you are an optimist in this incident. Always best to push things a little psst their intended range of use/stress in a comfortable and predictable location. And where better than in your own garage.

The alternative is to wait for an added stress to occur on the road in probably high summer when you are 50 to 100km from home. Then you would be wishing that you had deliberately 'tweaked' or 'upset' the pipes just to see if they were healthy.

Just my engineering knowledge methodology.

Brian McIlvenna
Brian McIlvenna

Paul, I agree Optimist gets my vote. I have read a lot of threads which talk about catastrophic oil leaks and engine failure and although I have an oil pressure gauge, obviously a desirable addition is to have an oil pressure warning light. I have been searching for a suitable T piece to enable an oil pressure warning switch as well as the oil pressure gauge to be connected and have found the this.

It may help others thinking about fitting a warning light


Andy Robinson

I have been looking for something like this for some time. I don't think MGB engines have 1/8 NPT threads in the block. They appear larger and coarser ?UNC
The standard adaptor seems to suggest this.
Michael Beswick

Michael and I spent a lot of time looking for an adapter, without any luck until on one of many browses I found the original part in America. He did have two (a misunderstanding led me to not getting both), but has since sold the other one. I have a bag of adapters and pipe ends, including the adapter on that site (which I did use successfully on a Celica when I wanted to check the dash pressure gauge against another gauge) but couldn't get a suitable combination for the MGB between hose and pipe. One of the problems is the very restricted space for a block adapter with switch, the other is the standard pipe and hose fittings. These are conical on the MGB at the block adapter and connector (flat at the gauge), but even if you use different gauge and hose ends there is still the problem of getting the right combinations of thread and seat. Some are tapered threads which is fine for a switch, but no good for hose and pipe fittings with either flat or conical ends.

Doing something with the cooler hoses is a possibility, although you still have the problem of finding something with the correct threads and seats. And although the gauge port is right next to the cooler hose i.e. immediately after the pump, the gauge senses pressure after the filter i.e. immediately before the bearings, not the pressure at that cooler pipe. To have it before the filter wouldn't give the same warning under certain circumstances. Mind you, that didn't stop the factory moving the V8 gauge pipe from the outlet of the filter to the outlet of the pump, to counteract owner paranoia about low oil pressures!

Paul Hunt

Thanks Paul for the info. I have found the following on the Moss Europe website under MGB, Electrical, Gauges & Instruments, Auxiliary Gauges & Sensors, T Piece Adaptor, Oil Pressure Gauge/Switch

Maybe this will work?

Andy Robinson

Andy - interesting, I hadn't come across that one before, probably because it is called a Y piece and the others are referred to as T pieces!

However I suspect the threads and seats will be the same as in that T piece and so not a direct replacement either. The MGB connector has two males and one female, whereas all these T/Y pieces have one male and two females, as in the attached.

With the Y connector you are still dependent on finding suitable adapters or fittings for the hose and gauge pipe.

Paul Hunt

I eventually bought a standard connector and from the assorted bits I have collected cut a spigot off that has the thread for the switch. A pal will braze them together!
Michael Beswick


In my continued quest to find the correct adaptor to enable a Oil Pressure warning switch to be fitted, I managed to track down the correct part from the USA. (see attached picture)

The part was used on US model MGB's fitted with Anti Run On Valve's The part number is BHH649 (Moss Part No 180-245) and although on the US Moss website it says it is no longer supplied the Little British Car Co was able to supply it
I ordered the part last Monday and it arrived today - the cost was $18.64 USD plus postage, so it will be around 20 for UK customers.

This may help others wanting to fit an oil pressure warning light.


Andy Robinson

Andy - that is the part I referred to last month, you did well to track one down, that page has never come up when I've searched on BHH649 in the past. Looks NOS. However I note the price today is $26.95!

Also a word of warning. One post elsewhere refers to the Moss number 180-245 saying he found several listed as part number 3H2424. However if you do a search on that number many do come up, but it is the T-piece for Midgets, which has three female ports, not the two males and one female that the MGB needs.
Paul Hunt

This thread was discussed between 28/01/2015 and 05/03/2015

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