66 Impala Brake Fluid Recommendation - Impala Tech
Brakes & Suspension Conversion Questions & more

 
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post #1 of 9 (permalink) Old 06-15-2019, 09:33 AM Thread Starter
 
 
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66 Impala Brake Fluid Recommendation

I have installed a complete new brake system on my 66 Impala SS including a disk brake conversion using the factory spindals.


I am trying to decide what brake fluid to go with. I read I should not use silicone DOT 5 since I had a brake booster with


vacuum. I am thinking of going with DOT 3 and 4 synthetic versus DOT 3 and 4 conventional.


Any recommendations would be appreciated.


Thanks,


Brian
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post #2 of 9 (permalink) Old 06-15-2019, 09:40 AM
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I like silicone because it won't take the paint off if you spill any but to each their own all work just fine.

Big Dave
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post #3 of 9 (permalink) Old 06-15-2019, 10:59 AM Thread Starter
 
 
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Dave,
As I mentioned I have brake booster which uses the engine vacuum. I read several articals indicating not to use silicone if the car uses a brake booster with vacuum. The following is one paragraph from an article:


Silicone brake fluid is also known as DOT 5 fluid (Department of Transportation). Our old trucks were originally filled with DOT 3 fluid. It is chemically based on triethylene glycol monomethyl ether (similar to antifreeze) but has a longer chain with a higher boiling point. DOT 4 fluid is chemically similar to DOT 3 but has a higher boiling point. The big differences are:
  • Silicone, when sucked through a leaking vacuum booster into an engine, burns to form silica sand and quickly wears down an engine's internal parts. Glycol burns harmlessly.
  • Silicone affects rubber brake components' “elastomers” differently than glycol and may not be compatible.
  • Silicone will not mix with water; glycol will.
  • Silicone will not lift paint; glycol will.
  • Silicone contamination in your shop will cause fisheyes in future paint jobs; glycol will not.
The following is a link to the full article: Silicone Brake Fluid


Since the system is completely new, I just wanted to see what made sense.


Thanks for your thoughts.


Brian
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post #4 of 9 (permalink) Old 06-15-2019, 12:05 PM
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No idea who dreamed up that urban myth.

Factory cars all have power brakes using a vacuum booster. They also all use DOT 5 because the federal government says so.

Silicone was developed to resist absorbing moisture which causes the aluminum piston to seize to the cast iron bore of the brake caliper (which is why almost all Corvettes now have stainless steel sleeves in their original Girling four piston fixed bridge calipers).

The difference between DOT 3 and DOT 5 isn't silicone but the boiling point of the fluid. Bigger brakes (you have 11 inch discs, Camaros have 12 inch discs and the newest Corvette has brakes that are bigger than 14 inches. These disc sizes grow because the cars are getting faster than ever (the new Camaro weighs as much as a BBC first gen Camaro but has nearly twice the horsepower out of a SBC, for a top speed of just under 180 mph). That amount of speed requires a bigger brake to stop it so bigger and bigger rotors. That energy (heat from friction) gets into the brake fluid. Brake fluid only works when it is an incompressible fluid, not as brake fluid vapor after being boiled. Because of this the boiling point keeps going up (since the Corvette can now top out at 204 mph I expect the brakes to get bigger again and the boiling point to rise).


As to the points you raised. If your seals fail and brake fluid is ingested into the motor you won't be driving much because you have no brakes. All seals are DOT 5 compliant. You don't want water in your brake fluid because it's boiling point is far to low, that is why they went to silicone to get rid of the water that the glycol absorbs from the atmosphere. DOT 5 brake fluid in a sealed brake fluid container won't cause fish eyes in your furniture painting projects which takes away from your car building time.

Ignore idiots that post this (as in who paints furniture when there are cars to build.

Big Dave
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post #5 of 9 (permalink) Old 06-15-2019, 12:25 PM Thread Starter
 
 
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Thanks Dave for your insight. Much appreciated.

Just to clarify, I think the article was implying the silicon could get suck through the booster brake vacuum line into the engine and due to the heat solidify to a sand type material causing damage to the engine.

Brian
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post #6 of 9 (permalink) Old 06-15-2019, 12:35 PM
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Quote:
Originally Posted by impalabrl1 View Post
Thanks Dave for your insight. Much appreciated.

Just to clarify, I think the article was implying the silicon could get suck through the booster brake vacuum line into the engine and due to the heat solidify to a sand type material causing damage to the engine.

Brian
Pseudoscience (aka witch-craft)

Sand is what remains of granite mountains which is in itself recycled basalt from volcanoes. There isn't enough heat or more importantly pressure (plus the need for time under heat and pressure to grow a crystalline structure) to convert the silicone found in brake fluid into Silicon Dioxide (quartz crystals known as sand).

Big Dave
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post #7 of 9 (permalink) Old 06-15-2019, 03:12 PM Thread Starter
 
 
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Thanks for your help Dave.

Brian
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post #8 of 9 (permalink) Old 06-20-2019, 04:33 AM
 
 
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Garage
Very helpful guys. Thanks for sharing
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post #9 of 9 (permalink) Old 06-20-2019, 10:37 AM
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Quote:
Originally Posted by Jim Trucksis View Post
Very helpful guys. Thanks for sharing
Funny how two out of three IP checkers have you located in Chiyoda, a suburb of Tokyo. One would almost think you where using a VPN to spoof your true location.

Big Dave.
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