Silicone Brake Fluid Replacement
Thread Starter
Melting Slicks
Joined: Jun 2005
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From: Siler City North Carolina
Silicone Brake Fluid Replacement
Has anyone replaced the dot 3 brake fluid in the C6 with the dot 5 silicone type? When I restored my 1967 I made the switch and it seems to work very well and does not absorb moisture. 
Le Mans Master
Joined: Dec 2004
Posts: 5,759
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From: AZ
St. Jude Donor '06-'08-'10-'11-'12-'13 '14-'15-'16-'17-'18-'19
Originally Posted by 67roadster
Has anyone replaced the dot 3 brake fluid in the C6 with the dot 5 silicone type? When I restored my 1967 I made the switch and it seems to work very well and does not absorb moisture.
Don't do it!!!
Le Mans Master
Joined: Aug 2000
Posts: 5,532
Likes: 1,947
From: Austin Texas
A) Dot 3, 4 and 5.1 are glycol based fluids that abosorb water vapor
B) Dot 5 is a silcone based fluid that does not absorb water vapor
It is extremely difficult to get dot 5 fluid into the system without putting microscopic bubbles into the fluid, one in they seemingly never come out, and these micro-bubbles will cause the brake pedal to feel a little squishy. To properly instal Dot 5 you need to preclean the system with denatured alcohol and then insert the fluid into the system with a pressurized bladder so that pressure is applied to the Dot 5 fluid but air is not. The rest of the process is just like a standard bleeding with a power bleeder.
If you want/need the high boiling point of Dot 5 (and you will if you start tracking the car), you can use Dot 5.1 just like any other Dot 3 or Dot 4 and none of the special bladder treatment. Ford HD, ATE SuperBlue/Gold (and several others) are all excellent glycol brake fluids, Castrol LMA is expensive but much less hydroscopic than the others.
In any event, if you start tracking the car, start changing (flushing) the fluids at least 4 tyimes a year and maybe as often as every track weekend, the crazies might even bleed the brakes between track runs.....
B) Dot 5 is a silcone based fluid that does not absorb water vapor
It is extremely difficult to get dot 5 fluid into the system without putting microscopic bubbles into the fluid, one in they seemingly never come out, and these micro-bubbles will cause the brake pedal to feel a little squishy. To properly instal Dot 5 you need to preclean the system with denatured alcohol and then insert the fluid into the system with a pressurized bladder so that pressure is applied to the Dot 5 fluid but air is not. The rest of the process is just like a standard bleeding with a power bleeder.
If you want/need the high boiling point of Dot 5 (and you will if you start tracking the car), you can use Dot 5.1 just like any other Dot 3 or Dot 4 and none of the special bladder treatment. Ford HD, ATE SuperBlue/Gold (and several others) are all excellent glycol brake fluids, Castrol LMA is expensive but much less hydroscopic than the others.
In any event, if you start tracking the car, start changing (flushing) the fluids at least 4 tyimes a year and maybe as often as every track weekend, the crazies might even bleed the brakes between track runs.....
Le Mans Master
Joined: Dec 2004
Posts: 5,759
Likes: 539
From: AZ
St. Jude Donor '06-'08-'10-'11-'12-'13 '14-'15-'16-'17-'18-'19
Originally Posted by MitchAlsup
A) Dot 3, 4 and 5.1 are glycol based fluids that abosorb water vapor
B) Dot 5 is a silcone based fluid that does not absorb water vapor
It is extremely difficult to get dot 5 fluid into the system without putting microscopic bubbles into the fluid, one in they seemingly never come out, and these micro-bubbles will cause the brake pedal to feel a little squishy. To properly instal Dot 5 you need to preclean the system with denatured alcohol and then insert the fluid into the system with a pressurized bladder so that pressure is applied to the Dot 5 fluid but air is not. The rest of the process is just like a standard bleeding with a power bleeder.
If you want/need the high boiling point of Dot 5 (and you will if you start tracking the car), you can use Dot 5.1 just like any other Dot 3 or Dot 4 and none of the special bladder treatment. Ford HD, ATE SuperBlue/Gold (and several others) are all excellent glycol brake fluids, Castrol LMA is expensive but much less hydroscopic than the others.
In any event, if you start tracking the car, start changing (flushing) the fluids at least 4 tyimes a year and maybe as often as every track weekend, the crazies might even bleed the brakes between track runs.....
B) Dot 5 is a silcone based fluid that does not absorb water vapor
It is extremely difficult to get dot 5 fluid into the system without putting microscopic bubbles into the fluid, one in they seemingly never come out, and these micro-bubbles will cause the brake pedal to feel a little squishy. To properly instal Dot 5 you need to preclean the system with denatured alcohol and then insert the fluid into the system with a pressurized bladder so that pressure is applied to the Dot 5 fluid but air is not. The rest of the process is just like a standard bleeding with a power bleeder.
If you want/need the high boiling point of Dot 5 (and you will if you start tracking the car), you can use Dot 5.1 just like any other Dot 3 or Dot 4 and none of the special bladder treatment. Ford HD, ATE SuperBlue/Gold (and several others) are all excellent glycol brake fluids, Castrol LMA is expensive but much less hydroscopic than the others.
In any event, if you start tracking the car, start changing (flushing) the fluids at least 4 tyimes a year and maybe as often as every track weekend, the crazies might even bleed the brakes between track runs.....
Also here is a link to read about DOT5 versus the others, hope this helps
http://www.conecrazy.org/tech/brake.html
Thread Starter
Melting Slicks
Joined: Jun 2005
Posts: 2,098
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From: Siler City North Carolina
This is what is so great about the forum, just pose the question before you make the mistake and you are sure to get sound advice! Thanks for the feedback, what has been good for the 67(because of paint issues etc.) obviously won't cut it for the 05, the web link clears up mystery for me as well. Enjoy the Ride!
Safety Car
Joined: Jul 2001
Posts: 4,456
Likes: 6
From: Spicewood, Texas, USA TX-Texas
Originally Posted by ByByBMW
My understanding is that the DOT 5 Silicone fluid is NOT, I repeat, NOT, compatible with modern ABS systems like those found on our C6.
Don't do it!!!
Don't do it!!!
Installation difficulty is substantial, but in this case, it's irrelevant. Silicone fluid entrains air, raising havoc with the ABS controller. Check the owner's manual...it may specifically say not to use silicone fluid in the brake system.
