Brake light switch query

[thefarmer]

I need to swap out a brake light switch on 67 cooper s. Can anyone tell me what size socket I need to undo the thing? All my sockets are too small, so I'll need to get one in... No room to get anything else on there except for a long socket.

Cheers
Ben

[ivor badger 2]

15/16" af or possibly a 24mm if you are only metric. Put a 5/8" af spanner on the banjo bolt under neath the switch to stop it unscrewing, then turn the switch from the top (above the top of the wing) with a long extension.

[ianh1968]

<SNIP>or possibly a 24mm if you are only metric.

People that work on Minis and only have metric tools
need a seriously good kicking... Do these people really exist?
(I worked on a Morris Minor a while back that had been professionally restored,
but was fitted with M6 sump retaining screws (and it leaked)).

I seem to remember that the way to undo these is to not push
the socket right onto the socket extension.

Do the terminals end up partially inside the 1/2" square?

You get plenty of turning force by just dropping the drive bar
lightly into the top of socket, without it being totally "clicked"
into position.

Does this make sense? I've never had/used a "long" socket...

Ian

[thefarmer]

15/16" af or possibly a 24mm if you are only metric. Put a 5/8" af spanner on the banjo bolt under neath the switch to stop it unscrewing, then turn the switch from the top (above the top of the wing) with a long extension.

Thanks for that.....I'll go and dig out the right size.

Cheers
Ben

[LarryLebel]

I use silicon hydraulic fluid so this operation is required every year or so because the DOT5 damages the switch for some reason. I remove the servo bracket bolts to move it out of the way. The hydraulic lines will bend as required.

[ianh1968]

I had the same problem as Larry with the DOT5.
In the end, I gave up and fitted a pedal-mount switch.

Ian

[dklawson]

I only replaced my car's hydraulic switch once after switching to DOT-5... then I converted to a pedal mounted switch. There's too much anecdotal evidence that the hydraulic switches fail when used with DOT-5 to keep buying the hydraulic switch.

[Spider]

I use silicon hydraulic fluid so this operation is required every year or so because the DOT5 damages the switch for some reason. I remove the servo bracket bolts to move it out of the way. The hydraulic lines will bend as required.

I'm not sure that it's the DOT-5 that causes this, it seems the common Hydraulic Switches these days don't last, I was lucky to get 3 months from them on DOT-4.

I've now gone over to a HELLA Branded switch, not cheap, but so far, so good, 4 years and still works.

[LarryLebel]

I have one more pressure switch to use up before I make the change over.

[ivor badger 2]

I use silicon hydraulic fluid so this operation is required every year or so because the DOT5 damages the switch for some reason. I remove the servo bracket bolts to move it out of the way. The hydraulic lines will bend as required.

So why don't you just use the correct brake fluid? If it's damaging the switch, it's damaging the seals

[1071bob]

Just had a look at my original Lucas switch, it's 1" not 15/16"

[ivor badger 2]

Just had a look at my original Lucas switch, it's 1" not 15/16"

sorry then, failing memory cause it's along time since I swapped one.

[Nick W]

I use silicon hydraulic fluid so this operation is required every year or so because the DOT5 damages the switch for some reason. I remove the servo bracket bolts to move it out of the way. The hydraulic lines will bend as required.

So why don't you just use the correct brake fluid? If it's damaging the switch, it's damaging the seals

Silicone brake fluid is obvoisly used so water isn't absorbed in to the brake system which causes rust if laid up for long periods
I've never used it though

[ivor badger 2]

I use silicon hydraulic fluid so this operation is required every year or so because the DOT5 damages the switch for some reason. I remove the servo bracket bolts to move it out of the way. The hydraulic lines will bend as required.

So why don't you just use the correct brake fluid? If it's damaging the switch, it's damaging the seals

Silicone brake fluid is obvoisly used so water isn't absorbed in to the brake system which causes rust if laid up for long periods
I've never used it though

Yes, but the mini system isn't designed to use it. Do you actually realise how long it has to be in the car before water absorbsion is a problem?

[smithyrc30]

Yes, but the mini system isn't designed to use it. Do you actually realise how long it has to be in the car before water absorbsion is a problem?

About 2 years in a 'normal' humidity market for DOT 4, 1 year to 18 months for tropical regions (If you define 'problem' as the BP falling below the minimum requirement). 4 absorbs water more quickly than 3. The standard measure for water absorption to test at is 3.5~3.7% at which point the 4 BP is down to 155C (minimum requirement, depends on what you started with). 3 will be down to 140C (again minimum requirement, depends on where you start).

Although 5 does not physically absorb the water, it still gets into the system through the hoses and seals so the issue of lowering the BP is still there. Also because it does not absorb it the water tends to 'localise' and because there are no corrosion inhibitors in 5 it can lead to localised corrosion issues. Copper does not get on with 5 particularly well either, which might explain why the switches fail (to an extent)

5 also has the issue of increased compressibility and a greater expansion when heated, so the brakes 'feel' spongier than with 4 and you need to lower the level in the MC to allow room for that expansion.

[dklawson]

DOT-5 is perfectly compatible with all common rubber brake seals. It is NOT compatible with silicone seals... which are not common on brake systems anyway.

If a piece of brake rubber (hose, seal, etc.) has ever been exposed to DOT-3 or DOT-4, it will "sluff off" (black gooey) material when used with DOT-5. That is why it is imperative to only switch to DOT-5 if you have flushed out all the metal lines and rebuilt all the wetted brake parts with new rubber (including hoses and things like the seals inside of PDWAs and brake limiter valves).

I acknowledge that DOT-5 does something to hydraulic brake light switches. Nothing I have read yet offers a suitable explanation for why this is so. However, it is my understanding that Harley-Davidson has been using DOT-5 on some of their motorcycles for a while and that their hydraulic brake light switch is not affected. Motorcycle owners, please correct me if that is wrong.

Moisture absorption with DOT-5 is pretty much a non-issue. It really does not pick up moisture if you keep the reservoir full to eliminate possible condensation in the air above the fluid. Every time I have heard someone complain about pooling water in DOT-5 systems it has turned out to be someone who did not flush the system thoroughly and left residual DOT-3 or DOT-4 behind.

Compressibility and entrapped air are issues with DOT-5. You can have a slightly spongier pedal. However, switching to braided brake hoses, careful pouring of the fluid, and careful bleeding of the system typically result in a very suitable pedal.

While I am pro DOT-5, I do NOT see it as a panacea for all cars and conditions. I reserve the use of DOT-5 to cars that see limited driving and/or are collector cars. In general the use of DOT-5 in a daily driver is not warranted since a complete flush and rebuild is necessary to use it. It's much easier to use DOT-3 or DOT-4 on a daily driver and adhere to a routine flushing schedule. While it is still important to flush DOT-5, the interval is longer. I have not seen a published number of months or years but I have replaced DOT-5 about every 7 years.

[mk1]

I have had DOT5 in my Sprint for 7 years now & the switch still works fine.

[ivor badger 2]

Having had the water absorption in the fluid with one car, non mini. The brakes failed one Sunday morning on a slightly twisty road. worked out what was wrong and let them cool and just stayed off the brakes for the rest of the day to keep them cool. The car had pent long periods of the road so was still on the original DOT3 because the brakes had never been worked on. How old was it when it happened, over 15 years.

[swindrum]

I rebuilt my MG1100 in 2004, at the time I used silicon fluid, yes, it is a bit spongier then DOT3, but, after being parked for 7 years and rushed back into service earlier this year, the brakes were as good as the day I parked it, and the hydraulic switch is still working. If I recall it was a NOS BMC switch

[ianh1968]

I use DOT5...

On the Marcos, brake switches were most definitely a problem,
but to be able to blame something in particular would be difficult.

As I said before, this is now history as a mechanical switch has been fitted.

For me the best thing about DOT5 is... (Well, let me tell you a little story...).

My car was "in bits", the clutch hydraulics were not connected, but the brakes were.
The brakes needed bleeding, and a mate of mine had come round.
"Great!", I thought, "I can use him to help me bleed the brakes".
I got all the pipes and jars etc set up and cracked open the first nipple.
"Down" - I called.
At this point, a rather large squirt of DOT5 came firing out of the top of the clutch master cylinder.
It was a sort of fountain, and it went all over the place, including the paintwork.
My mate crapped himself and looked more than slightly worried.
... priceless!
For a while, I kept a straight face, then after a suitably long pause I
nonchalantly went into the garage for a rag and then just wiped the mess up.

The moral of this tale is:
If you have your car in bits, you want to bleed the brakes and your mate
does not know the difference between the brake and the clutch pedal,
you are probably better off with DOT5.

For the record, the 'A' Series was not designed to be fitted with a Weber carb,
but people still fit them it anyway. It was also not designed to take 74.7mm
Triumph pistons to increase the capacity, but people still did that as well.

Each to his own...
...No point in getting angry if people want to do things differently!

Ian