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When to use Silicone Brake Fluid

2K views 4 replies 4 participants last post by  dmorris1200 
#1 ·
I am going to be changing the brake fluid. I presently am not using silicone fluid and a friend says he swears by silicone fluid. I need to know if silicone fluid is compatible with typicxal DOT3 or do I have to flush the system of feild strip the system before the new fluid is used? I don't want any clotting or other weird thing happening.
 
#2 ·
Silicone IS NOT compatible with anything else. It will gell when mixed with a mineral base, so you have to flush the system first. I always use alcohol (rubbing alcohol is fine). The only time I'd use silicone is if the vehicle isn't driven much. Silicone will absorb some air, and can give the pedal a spongy feel. But it doesn't absorb water, so the brake system should last longer. This isn't critical for a vehicle that's driven daily or at least 3-4 days a week, but if hte car sits for a length of time, like through the winter, you would probably benefit long term with silicone fluid. Just make sure you flush good first. Open bleeders on all four wheels and keep the reservoir filled with alcohol until you're passing straight alcohol, then pump dry. Put in silicone, then pump up and bleed until you have no air and straight fluid. I'd put a sticker on the booster or firewall somewhere warning that only DOT 5 silicone can be used. I accidentally put some DOT3 in mine, realized my mistake as I was pouring, quit, and quickly emptied the reservoir with a big syringe (a turkey injector). Should be okay, right? No. A couple days later I started having one wheel lock up. Had to flush the whole system out. I don't think I'll run silicone again, but had no other problems with it.
 
#4 ·
Thanks for the feedback. A friend of mine said he replaced the DOT 3 fluid with silicone in his Vette when silicone first came out and has not had any problems. Based on your comments, I'm going to stay with the old tonic to save time. Next winter I will reconsider the topic if I still have the car.
 
#5 ·
You should try using the 'search' feature at this site, works great to pull up old threads. You should take a look at this one at least. <a href="http://www.hotrodders.com/cgibin/ubb/18/001192/1" target="_blank">DOT 3 vs DOT 4</a>. If you really want to switch to something other than DOT3 or 4 maybe you should consider synthetic DOT5.1 instead of silicone. At least it's compatible with 3 and 4 so proper flushing isn't so critical. Just an idea. ;)


 
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