Brake light switch

[drooartz]

To test if the brake light problem was in the switch or in the lamps, I jumped the 2 wires going to the pressure switch (leads connecting the 2 screws on the switch). I figured that if the brake lights went on, then the problem was in the switch somehow. Once jumped, the brake lights came on. I'm figuring now that I need to replace the pressure switch? Can they be removed and cleaned, or is it just better to replace them?

 

[jlaird]

Replace, replace. Prob can even get one from a local source.

 

[spritenut]

It's probably 45 years old and they are cheap enough to replace.
Well the Lucas ones aren't cheap anymore but it's just a 3/8 x 24 thread pressure switch available at any auto store.

 

[drooartz]

Will removing this switch spill brake fluid everywhere? Need to bleed brakes when done?

 

[Bugeye58]

Drew, you may lose a thimbleful of fluid, and shouldn't have to bleed after the swap. Put a rag under the switch to catch any leakage, and you should be done in about 5 minutes. And, as mentioned, the switch is a standard automotive item, and should be available just about anywhere.
Jeff

 

[dklawson]

Remove the cap to the reservoir, cover the opening with Saran wrap and replace the cap prior to removing the switch. This will reduce the amount of leakage when you replace the switch. Don't forget to remove the plastic film when you're done.

Out of curiosity, did you switch to a different brake fluid... like silicone (DOT-5)? In the Mini community several of us have noticed that the pressure-type brake switches seem to fail when the switch is made to DOT-5 fluid. This is particularly fast and prevalent with old switches. New switches fail with DOT-5 also but seem to last a little longer. My fix was to mount a pedal actuated switch and wire it in parallel to the pressure switch. I'm just curious if the Spridget group has seen anything similar.

 

[Trevor Jessie]

I've heard that on other message boards, but I think some people like to ride the "bash silicon fluid" bandwagon. I have used it for 4 years now with no problems, but I have a pedal mounted switch.

 

[sparkydave]

/ubbthreads/images/graemlins/iagree.gif I have heard of the problems with the pressure switches, and this might be why they went with the pedal activated switches. I went with silicone too, and started with a completely dry system (new master cylinder, new hoses, new brake lines, and clean wheel cylinders). No troubles at all, and it works great. Given the age of the pressure switch, maybe it just got stuck from corrosion and some DOT 3 getting sludgy.

 

[drooartz]

[ QUOTE ]
Out of curiosity, did you switch to a different brake fluid... like silicone (DOT-5)?

[/ QUOTE ]

I have no idea what brake fluid is in the car--I've only owned the car for a few days. Is there an easy way to tell?

 

[jollyroger]

Stick your finger in the fluid and taste the tip. If it is bitter it is standard stuff. The silicone will taste kinda oily. No you won't die. But you may develop a slight twiwitich.

 

[Grantura_MKI]

OH BOY! /ubbthreads/images/graemlins/nonono.gif Go buy a pint of Castrol brake fluid and a shop manuel. If you put the wrong fluid in the system, it will eat out the seals.
Cheers, David.

 

[sparkydave]

The DOT 3 usually turns brown. Silicone starts out purple (yes, really) and pales a little. Also, DOT 3 has a definite smell to it whereas DOT 5 is pretty odorless (the quart I got from Moss is anyway).

 

[drooartz]

[ QUOTE ]
If you put the wrong fluid in the system, it will eat out the seals.

[/ QUOTE ]

The PO seemed pretty knowledgeable, so I'd guess he used the right stuff. I haven't touched the brake system yet, fixing this switch will be my first go with this part of the car. I think I'll call the PO today and see if he remembers what fluid he used last. Seem to remember that you shouldn't mix types.

And yes, I do have a shop manual--bought it before I had a car even--a little light reading. /ubbthreads/images/graemlins/grin.gif

 

[jollyroger]

Silicone will not eat the seals, not even the sea lions.

 

[zimmy]

thats funny drew! i had my book a month before my car made it to the yard also..; )........zimmy

 

[Trevor Jessie]

I've lost my one and only repair manual. It bordered on useless compared to the insight you can gain here and elsewhere on the web.

 

[dklawson]

Sea Lions... !!!!

The seal damage issue mentioned by David is not as clear as it used to be. There was a time when the only fluid you could use was DOT-4 LMA (Castrol). I understand that sometime in the 1970s BL changed the composition of the sealing rubber to something compatible with DOT-3. IF (and only if) you know that ALL the rubber in your car's braking system has been replaced since 1980 you should be able to run DOT-3. If in doubt, stick with DOT-4.

I won't offer to start the DOT-5 debate here. It always gets heated when brake fluid choice is discussed.

 

[Matthew E. Herd]

Dot 4 is superior to 3 in terms of temperature characteristics, and it's really not that much more expensive anyway. It's also compatible with DOT3, so if you aren't sure, just go for the marginally more expensive 4, and you're all set!