1961 leaking brake light switch

[Bob63]

After installing the second new master cylinder, cleaning and lubricating adjusters , checking wheel cylinders, bleeding master and all 4 wheels and installing a new brake light switch I finally have a good pedal. Now I find that the brake light switch is leaking allowing the pedal to get lower and lower. I’ve tried wrapping it with a couple of turns of Teflon tape but that hasn’t stopped the leak.
I hesitate to put gasket sealer on the threads but I’m not sure what other solution there might be.
Has anyone had this same problem and how did you solve it?

 

[59tbirddavid]

Go to a Harley Davidson dealer and purchase a brake switch from them . When I have time will get back to you with a part number. All the switches come from China, junk. Harley ‘s use silicon brake fluid as do I. Good switch, have had one in use for 5 yrs. Never got 6 mo. from part store part.

 

[Ward 57]

After installing the second new master cylinder, cleaning and lubricating adjusters , checking wheel cylinders, bleeding master and all 4 wheels and installing a new brake light switch I finally have a good pedal. Now I find that the brake light switch is leaking allowing the pedal to get lower and lower. I’ve tried wrapping it with a couple of turns of Teflon tape but that hasn’t stopped the leak.
I hesitate to put gasket sealer on the threads but I’m not sure what other solution there might be.
Has anyone had this same problem and how did you solve it?

Are you sure it isn't cross threaded or fully seated because of that if it's leaking around the treads? Two more things Most of the pressure switches I've delt with need to be primed as in putting brake fluid into the orifice before installing to eliminate any air in there. Second, Ordinary white Teflon tape is not resistant to chemicals and is only suitable for water applications. You need to use the yellow tape as it is resistant to fluids other than water.

 

[74 Harley]

Teflon tape is not a sealant! It is a lubricant. You need a thread sealant like Gasoila.

 

[59tbirddavid]

I said I would get back to you with info on brake switch used on Harley. It is 72023-51E. I use silicon brake fluid. Switches bought from internet or NAPA would last 6mo. Oil would get on the contact side of diaphragm and render switch useless.The receipt date is 7/25/2018 that is days away from 5 years. Price was $24.42. Don’t waste your time and money on the Chinese switchs.

 

[Yadkin]

I couldn't find a switch that worked without pressing down the brake pedal hard, so I gave up and rigged a spring switch between my brake pedal and point on the dash. Easy to adjust and I can flash my brakes with a light touch on the pedal.

 

[Ward 57]

I couldn't find a switch that worked without pressing down the brake pedal hard, so I gave up and rigged a spring switch between my brake pedal and point on the dash. Easy to adjust and I can flash my brakes with a light touch on the pedal.

Glad you came up with a solution. What I have found with pressure switches you have to 'prime' the switch before installing. I.E. fill the void in the switch with brake fluid first.

 

[Bob63]

Update: Here’s the rest of the story - I could never stop the leak from what I thought was the brake light switch so I pulled the master cylinder back out to check to be sure it hadn’t split or cracked at the switch port. What I found were some very small pin holes on the bottom of the casting just above the switch. When pedal pressure was applied the casting would leak and drip off of the brake light switch. I picked up another master cyl from Centric which appears to have a good casting. The leak may finally be resolved although time will tell.