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MG MGB Technical - Oil Pressure Warning Light

Last week on an A road at 70mph I saw I had no oil pressure. I managed to pull off into a bus stop killing the engine in the process – not fun at 70 mph with unimpressed cars behind. It just momentarily started to make an ominous noise…… . Turns out that the union on the oil pipe from the cooler to the filter had come apart where the pipe crimps onto the union.

When we got back, courtesy of the RAC, I drained the sump of what little oil was left ( less than a pint?) and took off the filter to cut it in half to get the oil out . Nothing showing in the oil from the sump but there is a very fine ‘silt’ from the oil filter - but I did cut with a Dremel. Engine still turns over OK with a spanner on the front.

I am planning on bypassing the cooler with the long hose, fill it up with oil, run it up and see what happens?

I also plan on having an oil warning light - it was only luck I saw it and it may give me more vital seconds. The obvious place to insert a pressure switch to me is to put a 'T' on the oil pressure gauge pipe on the bulkhead - any idea where I can get one? I think they are a Whitworth thread and the one fitted to US cars I think as part of the emissions thing is NLA

Cheers

Mike



Mike Dixon

Later North American spec had a Tee on the heater shelf with an oil pressure switch as you say. That was normally open and closed with pressure whereas a warning light needs a normally closed one of course. The tees do come up from time to time BHH649, I located a couple over there and got a pal to send me them for my roadster and V8, otherwise even if people over there are willing to post to the UK usually it costs a fortune.

After a lot of searching I did find an adapter and fitted it to a standard 2-port connector, if you are interested.
paulh4

Later North American spec had a Tee on the heater shelf with an oil pressure switch as you say. That was normally open and closed with pressure whereas a warning light needs a normally closed one of course. The tees do come up from time to time BHH649, I located a couple over there and got a pal to send me them for my roadster and V8, otherwise even if people over there are willing to post to the UK usually it costs a fortune.

After a lot of searching I did find a suitable adapter and fitted it to a standard 2-port connector, if you are interested.

As the roadster pressure is never normally below 25psi I fitted a 20psi switch to get the earliest possible warning - more expensive, but on the V8 it has to be a more conventional 5 or 6 psi. The higher pressure switches need careful research as more modern cars tend to use the normally open type, which can still be used with a little electrical jiggery-pokery.

It all depends on how bright the light is and where it is. Many years ago I wondered why a Scimitar GTE at Prescott hill climb had a big orange light on the dash - a Mini indicator, until he roared off the line and left a large and spreading pool of oil behind. I bought a kit-car led warning light which was not very bright and fitted a super-bright LED behind the lens, mounted on top of the cowl. Hopefully that's good enough.






paulh4

Thanks Paul.

I did think of going to a motorsport firm - they might be able to help but details of the adapter/connector you found would be useful



Mike Dixon

I looked at several from motorsports but got nowhere, it was finding a combination of bits that matched both the pipe/hose connectors and the switch. Elsewhere someone listed what he had done, but someone else said they didn't work.

So I started with the thread of the switch to look for an adapter I could fit to the original connector, and went from there. Ended up with Panam PRA-2N-1N-SS the first one here http://www.panamengineers.com/Reducing-Adapters-NPT.php Sourcing one was the next job, then searching for a suitable drill and tap.

Just looked in my bag of bits and do have one made up as well as an original BHH649 which I had forgotten about as it was a while ago.
paulh4

Hi Paul,

I would be interested in selling either can you PM me?

I cannot find out how to do it - sorry!

Mike
Mike Dixon

Mike
Have you tried Merlin Motorsport.
They do lots of parts including tee’s and adjustable oil pressure switches etc.

R.


https://www.merlinmotorsport.co.uk/s/instruments-gauges-senders/oil-t-pieces-line
richard b

Thanks - I may give them a go, they are only an hour or so away from me - I think it needs to be a visit with the pipe
Mike Dixon

Mike - can't see an email for you, email me at paul.hunt1@blueyonder.co.uk
paulh4

I use an adjustable pressure switch from a general hydraulic company. Set to 45 psi, comes on at idle when really hot but always of when on the move. Gives really good early warning, very useful for oil surge when competing.
Paul Walbran

Mike. Sorry to read about your problem. My daughter had the same problem a number of years ago when the three year old oil cooler on her 77B cracked and she lost oil pressure. When I drove over and traded cars with her (she was on her way back to college) she told me she had caught a glimpse of the oil pressure gauge dropping, had put the transmission in neutral, and pulled over to the side of the road where she turned the engine off. (North American specification vehicle have an ignition lock that, when moved to the off position, lock up the steering wheel. Very poor idea to try to switch off the engine when trying to get off the roadway.)

What I found when I arrived was no oil showing on the dipstick. When I refilled the crankcase, my daughter restarted the engine, covering me with oil under 75 psi pressure before she could turn the engine off. The crack in the hose allowed about three of the four quarts of oil in the sump to be sprayed out in the few seconds the engine was running.

Based on this experience, I found the following:

1. Having a "low oil pressure" warning light would not have made a difference. She was driving at night and actually saw the movement of the needle on the gauge as it rapidly dropped. With this form of rapid oil loss situation, a light is of only marginal value.

2. Even with having turned the engine off quickly, there was bearing knock on start up. And the rod and main bearings showed damage from being run with dropping oil pressure/loss of oil. (Engine had been rebuilt within the last year before she moved down to Tucson to attend college.) The crankshaft showed minor damage. The crankshaft was turned and oversized bearings installed on the main and rod journals. Engine still running fine some 19 years later.

3. I did away on the oil cooler that was on her vehicle. I had been running three other MGBs that did not have oil coolers installed, including driving them in the 40 deg. C and higher summer temperatures here. I did not notice the engine cylinder head temperature get any hotter when the oil cooler was bypassed. To me, it is just one more possible point of failure, and I have seen two failures with the oil cooler systems on two different MGBs.

Les
Les Bengtson

You surprise me saying the steering lock engages as soon as you turn off the ignition on a North American 77. AFAIK by that time all MGBs had the same steering rack and lock system and in my experience when you turn off the ignition the accessories circuit is still powered with the steering unlocked. Also AFAIK for many years prior to that you could not lock the steering inadvertently as there was either a series of in, out and turn movements needed (UK 73) or a push-button (75 V8) before the key can be removed, and it is only on removal of the key that the steering locks. Given all the safety features that American legislation demanded from very early on in the life of the MGB I'm amazed a dangerous feature like that locking with the key in and accessories circuits powered should be a specific requirement.

In a worst-case scenario an oil warning light may not always help, but there are many other situations where it will. Even with catastrophic oil loss as with that Scimitar I mentioned where the oil filter had blown off he got back to the pits, fitted a new filter, refilled with oil and set FTD on his next run.
paulh4

Mike, had you recently changed your oil cooler hose?

I had this failure twice(!), but at the block end - once in December having replaced the hose less then 6 months ago (which forum members kindly advised about - some checks seemed to indicate that I had got away with it without toasting my engine), but then the same thing happened (also on an A-road) with the replacement hose a few weeks ago, failing in exactly the same place.

Fingers crossed, I seem to have escaped damaging the engine this second time.

I've now got a different hose from a different manufacturer...
Nat

Braided? I won't use them and especially not for fuel after the hose cracked under the immaculate braiding.

Where did your failed replacement hose come from, Nat? Several years ago I spotted less than a pin-hole in one of mine that looks like it might have been original to the engine (the other indicating a 1987 date). There is one supplier I refuse to use despite (in fact 'because') being the cheapest. Bought Moss in 2015 stencilled 'Gates SAE R6/EN854 400 PSI'.
paulh4

Original hose was at least 18 years old and had developed a small hole. Both recent failed replacements were from Moss.
Nat

Er, right!
paulh4

The hose was non braided - I like to see what is going on, not that it would have helped me as it was the union next to the oil filter that came apart - poor construction? See picture in the first post.

I fitted the hose new this winter and it had only done 4000 or so miles.

The Engine is back with the builder - I am hoping it is just the bottom end shells and at worst a crank grind. We shall see.....
Mike Dixon

Mike
Just out of curiosity, the hose that broke---Did that fitting crack and break off or was it a case of not being crimped properly and worked it's way out.
I can't blow it up enough clearly to see but it looks like it's blown out-
William Revit

As far as I can see it was the crimp - no sign of any damage or cracking.
Mike Dixon

bugger-that's bad luck
We've got a mob here called Parker that do hose fittings and they do a push on barbed fitting called a Push-Lok, that takes up to 400psi without a clamp or any crimping
Easy, simple to make up hoses ,just push them on and that's it ,done finished
They're sold in the UK by Fluidpower, might be worth a look if you have a repeat failure-----

https://ph.parker.com/au/en/push-lok-hose-fittings
William Revit

Thanks they look as if they might be useful

Mike
Mike Dixon

Regarding an oil warning light, I see that bettercarlighting.co.uk are now selling led warning bulbs that flash. That should attract the driver's attention if it's bright enough.
Mike Howlett

The ones I got from a kit car place were nowhere near bright enough but I was able to substitute a super-bright LED in the holder. I have an audible warning on the brake fluid level warning, but you maybe wouldn't want that on oil pressure unless you added some more electrickery so that it only sounded after the ignition had been on for a period.
paulh4

I did buy a fixed red one from ebay but a lead fell off before I could fit it with no way of soldering them back on.

I like the idea of flashing, found these without the need to change the bulb:

https://uk.rs-online.com/web/p/panel-mount-indicators/0210440

Might give that a go
Mike Dixon

This thread was discussed between 13/06/2022 and 01/07/2022

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