Has anyone had any problems with silicone brake fluid? I have been fighting a problem for about 2 years. I think it is heat related(I know it is). My brakes tend to lock up when it gets hot. I know that silicone fluids are supposed to work better in high heat applications. I have used a similar set-up on the last 3 or 4 cars I have built. It has a AMC dual master cyl, Buick drums on front, 9 in. Ford rears. I am considering changing over to DOT 3 or 4 fluid. Another friend had the same problem and changed fluid and it fixed it.

Heat should not affect the way your brakes work unless you are employing the brakes all the time like in racing where you can get some brake fade. Silicone is a better heat tolerant chemical than traditional brake fluids and does not absorb moisture etc.

If your friends car was fixed by the change out...my guess is that he got rid of trapped air in the system by default. This is what it wrong with your system if the brakes react to heat. I have seen systems bled and literally gallons of fluid pumped throught and still air left in the system. Sometimes the location of the bleeder valve tells it all. If it isn't in the very top position of the attitude on the car....you have to take it off the car and tilt it so that all the air goes to the top where the valve is. I have seen this prolifically.

I just don't know of any down sides to using silicone.

Steve Jack
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Steve Jack
SOUTHEASTERN GOODGUYS REP

Thanks for all of the info. I was suspecting air in the lines all along, but after bleeding them about 4 times I was beginning to think it was something else. I haven't bled them yet, but I plan to this weekend. Thanks again. I will keep you guys informed. Steve

I put silicone fluid in the pickup when I built it in 95 and haven't had any problems at all with the brakes. That includes cruising Woodward Ave on a 100degree day with my foot on the brake for hours inching along in traffic or drag racing with major braking from over 100mph. I had never used it before except in a Harley so it has been an experiment for me. I like that it doesn't draw moisture and corrode parts and that it doesn't do anything to paint. I have heard that it shouldn't be used in high heat applications like road racing or circle racing but my experience is that it works great for general street use

Good question tho. If there is a safety reason not to use it, I'd like to know about it.

Hi Cabriolet
You have air locked in your brake system. You may have to gravity bleed your system or suck the air out with a vacuum bleeder. Silicone fluid is harder for me to bleed, but i have found that a vacuum bleeder works good. Start with the wheel thats closest to your Master Cyl. and work out to the furthest wheel. The only thing i had to get used to while bleeding silcone is that the pedal never gets real hard like DOT . But once you drive the car the pedal feels fine.
When you heat the air it expands and applys your brakes. Regards, HonestFrank
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"VEO DINDICE"

Hi HonestFrank,
Am I missing something here? I was taught to start at the farthest brake and work my way to the nearest. Is Silicone brake fluid different in that respect? Thanks.
Phil
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One man's treasure is another man's trash.

Hi Phil
If you are pushing the brake fluid thru (pumping the pedal)
then you start your bleeding at the furthest wheel (right rear) and work your way to the closest to master cyl. If you are sucking the fluid (hand vacuum pump) thru, then start at the closest finish at furthest. I have found that sucking the brake fluid works best for silicone. Why I'm not sure ? You were taught right. Regards,HonestFrank
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"VEO DINDICE"

Whew...I thought that maybe I had been away from brakes for too long. I rebuilt the clutch mc and slave cyliner on my goldwing last night, and ended up using a vacuum pump to get all the air out. Used DOT4 brake fluid, Honda doesn't recommend silicone for this app. Thanks.
Phil
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One man's treasure is another man's trash.

NEVER USE DOT 5 SILICONE FLUID!

It has several totally unacceptable characteristics for auto racing. We have tested many of the available silicone fluids always with the same results, brake failure. Silicone expands at elevated temperatures, which causes a spongy pedal. This expansion can be so severe that total system brake lockup can result. Some silicone fluids can attack seals in your system, so the wise choice is to stay with Dot 3 or 4 fluids.
i have never used silicone fluids, but saw this warning on www.brakeman.com
it is referring to race applications and he is trying to sell "HIS" brake fluid, so i don't know if it is applicable. i copied and pasted the warning from his page.
rickd
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project...39 ford pickup

Hi Rick
Thanks for the info. I use silicone brake fluid in fork lifts that run 24 hours a day 7 days a week never had fluid over heat (But this is not racing) The pedal is spongy but the silicone does not attack the rubber parts so it works great in constant use (Fork Lifts). I use DOT 3 in my cars. If you have a car thats going to be stored winters silicone would be good because your rubber in brake system would stay in good condition. Dot 3 if it should sit for 4 or 5 months your fluid would be black. Because its attacking the rubber. Regards,HonestFrank
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"VEO DINDICE"

hi honestfrank;
thanks for the info. i can't find the specs on dot 3 0r dot 4, what is the difference. can dot 4 be used in place of 3 or is there nothing to gain by switching unless i would go to silicone fluid?
thanks again
rickd :-)
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project...39 ford pickup

If I'm right, DOT4 can withstand more heat, and you can use it in place of DOT3.
Phil
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One man's treasure is another man's trash.