Silicone Brake fluid ,(Dot 5), not to be used in Hudson brake systems with new brake parts?

Rob Fayette

I'm running into an issue with silicone brake fluid.  A few months ago I bought a brake master cylinder for my stepdown.
It's a Raybestos MC3081 that I bought from Rock Auto.  On the cap where you put in the brake fluid it says " Use Dot 3/4 brake fluid only".  I guess I was subconsciously ignoring the warning and I installed it.  Today I went to install the brake light switch which is a Standard Motor Products SLS27 also from Rock Auto.  When I took it out of the box there is a note that says "This product is not approved for use with Silicon Brake Fluids".  I thought OK, I will buy from my local NAPA store, (which I have done many times in the past).  When I bought it I asked the counter guy at NAPA if he had heard of this problem with Silicone Brake Fluid and he said he hadn't.  When I got home and opened the Echlin SL134  from NAPA ,it had a note that said the same thing : "This product is not approved for use with Silicon Brake Fluids".  I'm not sure what to do.  I guess I may have to go back to using Dot 3 brake fluid.  The funny thing is  I put silicone brake fluid in a 55 Hudson I had and after 10 years the brake system still seemed like new. 
Any suggestions or knowledge on this ?
Thanks a lot.  Rob

5433HET

Years ago when I switched to silicone fluid,  I remember going thru several stop light switches before I found one that lasted. The brake lights would come on all by themselves when the car was parked!  Sorry I can't remember the details.....

Jay_G

I have had problems with faulty and leaking switches on my 53 when I used the Dot 5 stuff.  I finally flushed everything and went back to Dot 3.  No problems since then.  I also thought the brakes were spongy on Dot 5, but that could be me.

Jay 

JFromm

Have heard that a Harley Davidson brake light switch is not affected by silicone fluid. Talk to Paul Schuster for more info.

Lance

I know that Hydro Electric who makes the repop hydraulic convertible top systems for Hudson converts do not advise using dot 5 . They claim it will void any and all warrenties on their top pump rebuilds and hydraulic top and window cylinders

50C8DAN

I have Dot 5 for over 14 years and I put in the Harley Davidson switch.  Yes, a normal one will fail in about 1 to 2 years.

RichardD

I use a lever switch; more reliable.

40indianssgmailcom

 1993  and newer Harley's require dot 5 as noted on the front brake master cylinder cap

54coupe

Get the switch from Paul. It was designed for Dot 5.

PAULARGETYPE

 ROB WHAT I'M USING IS A HARLEY BRAKE LIGHT SWITCH THESE ARE MADE FOE DOT 5 I GET THEM FROM THE SAME PLACE HARLEY DOES  THEY CHARGE $48  YOU CAN GET THEM FROM ME FOR $23 

Rob Fayette

Thanks for every bodies input.  You're input has made me decide to not go with Dot 5 and go with Dot 4 instead.
Thank
Rob 

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pseftoncomcastnet

Paul S. -- what is your long term experience with DOT 5 with the Harley switch? I recently  installed such a switch. Haven't noticed any issues with system leaks but these stories make me nervous.

40indianssgmailcom

I have long term experience with dot5 in my 93 Harley, never a leak and solid braking, not mushy. Have also used it in my v8 mgb and my 47 Hudson pickup with jaguar xj6 ifs and irs.  Same good pedal and no leaks.  Dot5 does not destroy paint like 3&4 nor does it attract moisture.  

pseftoncomcastnet

good to hear. I had some issues with seepage when I installed DOT 5 in a new system on my 51 Commodore. But I resolved them by loosening and re-tightening the connections. Seems fluid-tight now.

jjbubaboy

I also am working on my brakes. I was thinking of using DOT 3 synthetic.
Anyone have input/experience with it?
Thanks,
Jeff