Silicone Brake Fluid & lectricity

[Bill Traill]

Mark, After converting my 1967 MGB/GT to silicone I went thru about 6 stop-light switches in a year. I made a new thicker banjo bolt for the TC's master cylinder to incorporate a pressure switch. Same (silicone) problem....went thru 4 switches... but the last switch has lasted about 5 years. The successful unit was mid 1950's Ford cross matched to a "Intermotor (Nottingham England) #51600 brake light switch" available at my local auto supply. Also, in my MGB I replaced the "bi-metallic strip" fuel gauge voltage regulator three times. The first one lasted 17 years before the silicone brake fluid conversion and then failed within three months. I believe the silicone fluid creeps from the master cylinder around to the regulator and infiltrates to the points. This regulator is just on the other side of the bulkhead from the master cylinder and a mounting screw goes thru to the other side. After talking to TA Terry (note his prior post)....I took one regulator apart, cleaned the points, and it worked for a few weeks. Symptoms: after a few weeks the needle begins to indicate less and less actual fuel level and continually swings to and fro until it moves no more. No obvious silicone leakage. Prior I had changed the gauge, sending unit and checked the wires for shorts. A new regulator was thickly coated in shellac but the car is retired for now, so can't say how it will work. AND, don't use silicone in the MGB clutch system!!! The throw-out did not release completely and totally ground the bearing and carrier to dust in 300 miles. Quick story during my MGB / silicone experience..... I got a fix-it-ticket for inoperable stop lamps...waited the 30 days to get it signed off (procrastination) and while a law officer watched, it failed again! As it was 8PM I had to scramble to get a new switch and get that ticket signed off by mid-night and in the mail!! Bill Traill DCO: TC#5221 B/GT #99514

> Hi All, > > wrt the thread on silicone brake fluid, when my Dad (sadly no longer > with us) changed TC1459's brakes over about eight years ago, he had to > have the master cylinder piston machined down by 50thou, due to the > brakes binding on problem. No problems since, and no brake seizing > during periods of inactivity. At the time, we heard that the binding > problem could be caused by using a system that originally had glycol > fluid without fitting new seals. > > More recently, I changed my '72 BGT over to silicone. Also fitted all > new lines, hoses, master cylinder, calipers etc, and no binding. But I > do have a problem in that the brake light switch seems to fail, so > that over a period of time (about 15 months) I need to hit the brakes > harder for the lights to come on. Any ideas on why? Perhaps I should > just fit a mechanical switch a la TC!!! > > Regards, > Mark > TC1459 >

[Steve Rankin]

Bill I'm confused about how you could blame silicone for the MGB clutch problem. In my limited experience I was under the impression that liquids are incompressible. Unless you had air in the system, leaks, or some other malfunction, it would be difficult to understand. Anyhow, I changed to silicone in one of my B's last summer, so I guess I'll find out the hard way! Steve Rankin TC 6646

----- Original Message ----- From: "Bill Traill" bill@clovermachine.com> To: mg-tabc@yahoogroups.com> Sent: Thursday, December 13, 2001 2:01 PM Subject: [mg-tabc] Silicone Brake Fluid & lectricity > Mark, > After converting my 1967 MGB/GT to silicone I went thru about 6 > stop-light switches in a year. > > I made a new thicker banjo bolt for the TC's master cylinder to > incorporate a pressure switch. Same (silicone) problem....went thru > 4 switches... but the last switch has lasted about 5 years. The > successful unit was mid 1950's Ford cross matched to a > "Intermotor (Nottingham England) #51600 brake light switch" > available at my local auto supply. > > Also, in my MGB I replaced the "bi-metallic strip" fuel gauge > voltage regulator three times. The first one lasted 17 years before > the silicone brake fluid conversion and then failed within three > months. I believe the silicone fluid creeps from the master cylinder > around to the regulator and infiltrates to the points. This regulator is > just on the other side of the bulkhead from the master cylinder and > a mounting screw goes thru to the other side. > > After talking to TA Terry (note his prior post)....I took one regulator > apart, cleaned the points, and it worked for a few weeks. > Symptoms: after a few weeks the needle begins to indicate less > and less actual fuel level and continually swings to and fro until it > moves no more. No obvious silicone leakage. Prior I had changed > the gauge, sending unit and checked the wires for shorts. A new > regulator was thickly coated in shellac but the car is retired for > now, so can't say how it will work. > > AND, don't use silicone in the MGB clutch system!!! The throw-out > did not release completely and totally ground the bearing and > carrier to dust in 300 miles. > > Quick story during my MGB / silicone experience..... > I got a fix-it-ticket for inoperable stop lamps...waited the 30 days to > get it signed off (procrastination) and while a law officer watched, it > failed again! As it was 8PM I had to scramble to get a new switch > and get that ticket signed off by mid-night and in the mail!! > > Bill Traill > DCO: > TC#5221 > B/GT #99514 > > > > > > > Hi All, > > > > wrt the thread on silicone brake fluid, when my Dad (sadly no longer > > with us) changed TC1459's brakes over about eight years ago, he had to > > have the master cylinder piston machined down by 50thou, due to the > > brakes binding on problem. No problems since, and no brake seizing > > during periods of inactivity. At the time, we heard that the binding > > problem could be caused by using a system that originally had glycol > > fluid without fitting new seals. > > > > More recently, I changed my '72 BGT over to silicone. Also fitted all > > new lines, hoses, master cylinder, calipers etc, and no binding. But I > > do have a problem in that the brake light switch seems to fail, so > > that over a period of time (about 15 months) I need to hit the brakes > > harder for the lights to come on. Any ideas on why? Perhaps I should > > just fit a mechanical switch a la TC!!! > > > > Regards, > > Mark > > TC1459 > > > > > > > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > > >