Front Brake Light Switch Removal

[John T]

Gentlemen:  Need some advice please. Trying to remove from a 1979 R65 the front brake light switch. Have been using penetrating fluid (Snowbum mix) but so far, it's not budging.

Dare I apply a torch to the area near the threads?  On this model, switch attaches to a 3-way distribution piece.

Here is link to RealOEM diagram:   https://tinyurl.com/ycamf2zs

Appreciate your thoughts/suggestions.

[Justin B.]

Maybe try some Kroil penetrant?  I'm not sure whether you want to "save" but heat might mess it up depending on what the internal diaphragm is made of.  If it doesn't matter then remove the block (minus lines) and try heat, twist it off, drill out...

[Tony Smith]

Do you have the original brake lines or has it been retrofitted with banjo connectors?

If you have banjos your troubles are over, just buy a special banjo bolt with a brake switch built in.

https://www.ebay.com.au/itm/Hydraulic-Brake-Pressure-Light-Switch-10X1-25mm-Banjo-Bolt-For-Suzuki-Yamaha-Hot/132399414078?epid=13017014851&hash=item1ed39ebb3e

[tiggum]

That is interesting..........I have never seen the switch you have shown us, and so I went to the microfiche from MAX BMW.  Fiche says used through 09-80; then they evidently went to the later master cylinder/front brake control with the brake switch located by the brake lever pivot point.   Frankly, that looks like a great option, because....(and this is really timely, guys).....

I am currently recommissioning a 1983 R65LS, which had been stored full of fluids for almost all of its life.  Hydraulics have been solidly blocked with gummy old brake fluid and I am trying to get the system back in operating order, but it looks as if this is not going to be an option.  Thus, I have acquired from a friend an NOS replacement which was destined for a late-model R100RT but never installed.  However, it did not come with a switch and since it is integral with its cable and connector, the BMW price here in the USA is almost $65 (vs. the $13 and change the old one cost).  I have been looking on line this AM and was about to order one when this thread came in.  All I can say is THANK YOU VERY MUCH!  I have the same junction bloc for my front brake piping and one leg is plugged, so if I can get one of these switches, and install it in the junction bloc instead of the plug I can adapt my wiring (which remains in place and in fine condition) and I'm done.  Would it be likely that such a switch is also available for older cars at auto parts houses?  I may just take the junction bloc and go shopping in the next couple of days.

[John T]

Thanks for the input, guys. For the moment, I'll keep trying penetrating fluid. Plan B to follow...

A substitute replacement switch is, I believe, available from Autozone: Duralast Stoplight Switch RB401, for around $11.50.

Thanks

[tiggum]

Thanks for the lead on the alternate switch, John T.  I will go by AutoZone today and see.

[Tony Smith]

The penny just dropped. I didn't fully comprehend that the OP has the brake fluid "distributor" model.

In which case, yes a suitable switch is easily and cheaply obtainable. I would disconnect all lines to the "distributor", take it out and have at it with heat and maybe even freeeze spray. Even if you have to totally destroy the existing switch to remove it Tineserts will not leak.

[tiggum]

Yes, that distribution piece is cast brass (or maybe bronze) and mine is as in the diagram shown above; four ports, allowing for line in from M/C, line out to right disc, line out to left disc and #4 with a threaded plug, which can be removed to allow the switch.

I went to look for the switch today, but the nearby AutoZone store did not stock it (available from their distribution center in Memphis; cost $9.95 plus tax).  Went to see my friends at the local NAPA store; they cross-referenced the Duralast part number and brought out 2 options; both were rather large but worth a try for the price, but when I tried them they both threaded right into the bloc for about 2 turns maximum and then stopped, whereas the original plug which came in the casting  threads right in.  What's up  with that?  I seem to remember that the threads of some hydraulic and/or plumbing pieces are designed to gradually increase in diameter the further in they are threaded, to make a TIGHT connection...........is that the case for these pieces?  I don't want to destroy the casting, and have tried the threaded plug in all of the other three ports.  It threads in, just like it did originally in the fourth port, for just about 6 full turns, where it finally bottoms out.

Sure would like your thoughts about this.

[Tony Smith]

Many brake light switches use a tapered "gas" thread, whereas the "distributor" uses a paralell 10mm thread. I suspect at least one of the ones you have is a tapered thread.

[tiggum]

Tony, thanks for your response......yes, now I remember hearing about "gas" threads (when I told my wife the term she looked at me and giggled, saying "how appropriate for you"; Women!).

Anyhow, all four of the threaded ports appear to be of the straight variety.  The new brake hoses thread into the central two ports (those at the bottom) and thread all the way in until the shoulder on the fitting bottoms on the distributor.  Same for the hose which will link the master cylinder to the distributor.  So, I need to find out whether or not there are some switches with straight threads.  Anybody out there a mechanical engineer?

[Tony Smith]

So, I need to find out whether or not there are some switches with straight threads.  Anybody out there a mechanical engineer?

Motobins Code: 75400   
BMW: 61 31 1 244 334