silicone brake fluid proof brake light switch

S

Sal

Senior Member
The silicone brake fluid I use in my early Ford ruined the original stop light switch. Some one said Harley Davidson has a switch that will go on the master cylinder that holds up to silicone brake fluid. Does anyone know the H-D part number for it?
 
Sal, I have been using the HD for years, can't remember the part number but bring the Ford switch in and they will match it. If I remember the ends on your wires will have to be changed for the HD switch. Regards, Rick
 
How did the stop light switch fail? Quit switching, start leaking, plugged up with gunk? Several of the local guys are running silicone fluid and I'd like to know what to look for.

Thanks!
 
Sal said:
The silicone brake fluid I use in my early Ford ruined the original stop light switch. Some one said Harley Davidson has a switch that will go on the master cylinder that holds up to silicone brake fluid. Does anyone know the H-D part number for it?
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Suggestion below! DD

Ron Francis sells a silicone compatible switch that has been mentioned here several times.

http://www.ronfrancis.com/prodinfo.asp?number=SW%2D32

SW-32-Md.jpg


Item Number: SW-32
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Unit Price: $28.95
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In Stock
 
I always use the mechanical lever switch that was used on the older Chev. pickups. Never had a problem with them.
 
I have had two of Ron Francis's swithes fail, so far none of the HD switches have failed? when they failed the silicon got thru the seperation and hydro locked making the switch not work-how do I know this, I drilled on of the switches and fluid ran out, after letting the fluid out the switch worked
 
alanwoodieman said:
I have had two of Ron Francis's swithes fail, so far none of the HD switches have failed? when they failed the silicon got thru the seperation and hydro locked making the switch not work-how do I know this, I drilled on of the switches and fluid ran out, after letting the fluid out the switch worked
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My situation exactly the opposite two failed Harley D switches and been running the Ron Francis switch successfully last 5 years. Odd. Make sure the ron Francis switch is the silicon compatible one.
 
I went through 2 or 3 of those Harley switches as well. Soon as they leak a little, it contaminates the contacts. I finally gave up and rigged a mechanical switch in front of the brake linkage. Problem solved!
 
So the moral to this thread's story like others similar is DOT-5 silicone brake fluid sucks and don't use it in your old vehicle. Keep using the lesser DOT spec and change it periodically like you do your other fluids. Got it.

Lonnie
 
I've had silicon brake fluid in my '46 for 25 + years and have had no issues. Replaced brake switch one time due to being inop. I use NOS Delco 4766 switches. Have'nt used the new replacements.
 
I've had silicone brake fluid and same switch for over 12 yrs and no problems. Can't remember where I got the switch. Probably NAPA.
 
I bought an original '37 Chevy in 1993, flushed the system and installed Silicone brake fluid. I never changed the brake light switch at that time or since. I drain & install new DOT5 fluid about every 7-years or so, changed brake shoes and one drum in the interim, but I still have the same brake light switch installed.

I have no idea if it's the one that came from the factory, but I do know it was old when I got the car in '93 and it's never missed a beat in 21-years and thousands of miles of driving.
 
Binx said:
So the moral to this thread's story like others similar is DOT-5 silicone brake fluid sucks and don't use it in your old vehicle. Keep using the lesser DOT spec and change it periodically like you do your other fluids. Got it.

Lonnie
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Well you make it sound easy to eliminate the brake switch problem but I think silicon brake fluid is well worth the glitch. Try to make a long story short but I know it won't happen. Forty years ago when I had my block garage shop built and I didn't get it properly insulated or heated at first I had a lot of issues with moisture especially during "January thaws". Actually the "46 Ford coupe I had at the time had issues sweating in the damp condensation when high and low temps meet. I had problems with every wheel cylinder sticking in a very short period of time,one time I burnt paint or bubbled it off the wheel itself around wheel stripes before I got back home. Went through a lot of brake line cleaning,reworking cylinders etc. Really didn't know much about silicon brake fluid back then and never used it on the 46 but I did on the next project a '53 F-100.By then in the early eighties some info like in Old Cars Weekly addressed its merits. Just recently the man who bought the '53 from me in 1990 called and asked about the electric fuel pump that went bad. I told him it was probably the ethanol gas that probably ate it up,surprised,shocked actually when he told me the gas in the tank was what I had put in,he never drove or even started the engine. So fuel problem issue is a no brainer.His pole barn was uninsulated or heated truck had other issues it sounds like,rodents etc,what a shame. Finally the moral to my story, brakes he said seems to be fine,nothing stuck as rolled truck outside. Silicon brake fluid I installed in the eighties,not one cylinder (piston) stuck. I doubt if the original type switch works as at that time I wouldn't have had an option. I will accept the once in awhile failure well over a complete brake rework. Again the only failures I have had were a couple original switches and two HD ones.
 
We are going through this same problem ,wheel cylinders were sleeved in stainless new cups but the silicone fluid is leaking past ?? We think to course of a honing pattern .Ted
 
I had a lot of problems with the brake cylinders, I had to even replace the master cylinder as the bore was so rusty with using the ordinary brake fluid in our 1947 Ford coupe in the 1970's, as the car was not used regularly. So I replaced the brake fluid with silicone fluid and have had no trouble since. I also have had trouble with the brake light switches and since I have replaced it with a Harley Davidson switch I have had no more problems. What I have found since our coupe is not used very often every month or two it is best to give the brake pedal a pump up to bring the pedal up and to make sure every thing is ok.
 
FlatheadTed said:
We are going through this same problem ,wheel cylinders were sleeved in stainless new cups but the silicone fluid is leaking past ?? We think to course of a honing pattern .Ted
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Bad cups? Have you considered a residual valve to maintain some pressure on the wheel cylinders?
 
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