Morris Minor Owners Club

bmcecosse wrote:Just use the 'slowing down' hand signal!

Now how many people would know what that meant these days, it would probably end in a 'Road Rage' incident

Anyway, switch ordered. Hopefully the correct one, a Lucas C16062A for a 'classic' mini, single pipe braking system which looks pretty much identical to the Minor system

Let me know if the thread is correct please........

Will do, I have been away for a couple of days and it's arrived in the post so will get to try it soon

bmcecosse wrote:Let me know if the thread is correct please........

Well, it's not the same. The thread on the Lucas SMB423 'Classic Mini' Brake pedal switch is a finer pitch and is shorter.

Back to the drawing board on this one.

I rather thought so - the Mini uses 3/8" UNF threads - the Minor has a 3/8" BSF thread on the brake pipes in that area - but I just wasn't sure if the top fitting where the switch fits would be UNF to suit standard switch.

The consensus opinion is that the diaphragm inside the switch starts to fail if you need to press the pedal hard to get the brake lights to come on and will eventually fail.

So, have ordered another switch via Chris at 'Tom Roy' and will let you know if it makes a difference once received and fitted.

OK, the plot as they say, thickens.

The switch from Tom Roy appears to be the same as the mini one so it's looking like a different 'T Piece' and brake pipe fittings have been used.

The new switch only goes in about 1-1.5 turns before it's 'tight' and I don't want to force it in case it strips the Tee Piece

Anyone got any idea what the original is from?

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Hi,

Is it me or does your new switch look to have a tapered thread? the old one looks to have a straight thread on it? If that is the case then thats why it only screws in 1-1.5 turns and wont fit.

You can all laugh at me if I am wrong.....
Richard

C6Dave wrote:OK, the plot as they say, thickens.

The switch from Tom Roy appears to be the same as the mini one so it's looking like a different 'T Piece' and brake pipe fittings have been used.

The new switch only goes in about 1-1.5 turns before it's 'tight' and I don't want to force it in case it strips the Tee Piece

Anyone got any idea what the original is from?

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If you take a look at the bull motif website Dave they show 2 variants, they specifically mention taper threads.
I dont like taper threads, especially grease nipple taper threads

Yes that 'new' one looks like a UNF thread (but not tapered) and the old one clearly is the BSF thread. I believe there was a change sometime along the way....... I've argued this before - but always been assured it is BSF threads all the way..... I don't believe it!

The problem is then that all the main suppliers say a BSF one isn't available so may have to look for an Austin one possibly

Another possibility is an adaptor.
The new switch looks like 1/8" NPT thread.

Done a bit more research and after measuring the new one with a micrometer it is 'tapered' (10mm at the end increasing by +0.15 mm toward the head) so may actually fit using a bit of PTFE tape to seal and Bill who restored the car, confirmed by e mail that all the parts used were for a Minor.

Just depends how brave I feel tightening the new one in...........

It's BRAKES - a Safety Critical item.... DO NOT attempt a bodge with thread tape. Get the right switch......

C6Dave wrote:The problem is then that all the main suppliers say a BSF one isn't available so may have to look for an Austin one possibly

I googled "morris minor bsf brake light switch" and ESM popped up, they specifically mention bsf, hope that helps, they may be worth a call Dave.

What was I saying in the "where to buy a car?" thread about bodged brakes?

Might the new switch be M10 x 1.0 ? Can you try a thread gauge on them both? 3/8 BSF is 20tpi, 3/8 UNF IS 24TPI, 1/8 NPTF is 27tpi, and 1/8 BSP is 28tpi. Or just count threads against a steel rule.

It looks like at least one of the other branches of the adaptor is UNF (the little nicks out of the corners of the nut are the giveaway).

Kevin

OK called ESM and they sell an 'adapter' kit so have ordered one of those this morning so will feedback on the outcome

Sorry this has dragged on a bit but I realised that I hadn't got any brake fluid for the job......

Then I remembered I had read somewhere that 'silicone' fluid had been used so needed to double check with the person who rebuilt the car.

I got the reply over the weekend confirming that Dot 5 Silicone Brake fluid had been used. Being a Bank Holiday I immediately ordered some online as I couldn't find a stockist anywhere near me and it only arrived today.

Now I felt a bit braver so tried the new switch from Tom Roy again and this time wound it in carefully with a spanner.

Removed it and it had gone in over half the thread length before finally getting tight.

Now as the thread is tapered on the new switch and it was going to be anodised thread to brass fitting, I did use some PTFE tape (which is a fully acceptable hydraulic joint sealing solution and has been since I served my time back in the 1960's) to ensure a good seal between the Tee and switch, which will also negate any potential chemical reactions.

Now for a tip

I bought a glass eyedropper from my local Coop chemist for £1.01 and used that to pre-fill the hole in the switch with brake fluid and ensure that the brass Tee on the car was full to the top with no air in, before I fitted the new switch, so avoiding any air pocket

Oh and the 'adapter from ESM is going back for a refund.

EDIT: forgot to add that you can't mix Dot 3 4 and 5.1 synthetic based fluids with Dot 5 Silicone based ones

Just out of interest, did you check the pitch of either the new or old switches?

Kevin

The new one is correct Morris Minor standard UNF. Only very early cars might have anything different

The problem was the taper on the new v the straight thread of the old one