brake fluid
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Joined: May 2004
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From: NJ
brake fluid
Am i boiling the fluid? here are my symptons. At low speeds less than 40 mpg, breaks are sharp and firm. at higher speeds 65+, they feel a bit soft. But not soft like there is air in the system. They do stop the car good, But there is no veriation in the braking. I either use alot of force on the pedel and they stop well, or they feel soft. I have eradi speed plus rotors and hawk hp+ pads. also have steel lines. all with about 7000 miles on them. does this sound like a fluid problem? if so, any recamendations for fluid?
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Joined: Sep 2002
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http://www.superchevy.com/technical/.../0509sc_fluid/
SILICONE BASE BRAKE FLUID (SBBF)
The U.S. DOT defines silicone brake fluid as that which consists of no less than 70 percent of adiorgano polysiloxane by weight. Silicone-based fluids are regarded as DOT 5 fluids. They are highly compressible and can give the driver the feeling of a spongy pedal. The higher the brake system temperature, the more the compressibility of the fluid--increasing the feeling of a spongy pedal. Silicone-based fluids are non-hydroscopic, meaning that they will not absorb or mix with water. When water is present in the brake system, it will create a water/fluid/water/fluid situation. Because water boils at approximately 212 degrees F, the ability of the brake system to operate correctly decreases, and the steam created from boiling water adds air to the system. It is important to remember that water may be present in any brake system. Therefore, silicone brake fluid lacks the ability to deal with moisture and will dramatically decrease a brake systems performance. Silicone brake fluid has a number of strengths and drawbacks.
Strengths:
1) It has a high boiling point since it does not absorb water. Therefore, there's no so-called wet boiling point.
2) Doesn't absorb moisture.
3) Doesn't remove paint.
4) The viscosity is more stable over the extremes of temperature.
5) With the exception of some formulations used in external boots, silicone brake fluid is compatible with all standard brake components.
Drawbacks:
1) It's hard to pour without entraining air bubbles--hence an application will generally have a softer, spongier pedal feel.
2) It doesn't absorb water, so any water already in the system accu-mulates in the lowest point of the system and stays there, causing rust.
3) Glycol fluids begin to compress near their boiling points, whereas silicone fluids begin to compress at around 300-350 degrees Fahrenheit.
4) Additives in the fluid can vaporize at comparatively moderate temperature, increasing the spongy feel.
5) Silicone fluids expand significantly when hot.
6) Silicone fluid is functionally incompatible with systems that have held glycol-based fluids for any length of time, requiring flushing and seal replacement (there are counter opinions on this, which state that the modern silicone formulations are in fact compatible with only a flushing, rather than a complete reseal). The actual DOT specification requires chemical compatibility, so as far as that goes, the two fluids won't cause reactions if used in the same system, but they certainly won't mix, either.
7) It's pretty much incompatible with anti-lock brakes because the silicone fluids tend to be more viscous, which can cause problems with the timing of the pulses that are intended to work with the thinner glycol-base fluid. This sometimes leads to damage of the ABS valving. The rapid pulsing necessary to anti-lock functions tend to cavitate the fluid, as the tiny bubbles collapse and coalesce into larger ones, and then collapse and reform into smaller ones. This tends to counteract the ABS effect and can diminish the actual effective braking. This condition also heats the fluid and can lead to even more sponginess and possible damage to the ABS controller. Thirdly, silicone brake fluid tends to foam when expressed from a small orifice under pressure, reducing its hydraulic effectiveness greatly.
SILICONE BASE BRAKE FLUID (SBBF)
The U.S. DOT defines silicone brake fluid as that which consists of no less than 70 percent of adiorgano polysiloxane by weight. Silicone-based fluids are regarded as DOT 5 fluids. They are highly compressible and can give the driver the feeling of a spongy pedal. The higher the brake system temperature, the more the compressibility of the fluid--increasing the feeling of a spongy pedal. Silicone-based fluids are non-hydroscopic, meaning that they will not absorb or mix with water. When water is present in the brake system, it will create a water/fluid/water/fluid situation. Because water boils at approximately 212 degrees F, the ability of the brake system to operate correctly decreases, and the steam created from boiling water adds air to the system. It is important to remember that water may be present in any brake system. Therefore, silicone brake fluid lacks the ability to deal with moisture and will dramatically decrease a brake systems performance. Silicone brake fluid has a number of strengths and drawbacks.
Strengths:
1) It has a high boiling point since it does not absorb water. Therefore, there's no so-called wet boiling point.
2) Doesn't absorb moisture.
3) Doesn't remove paint.
4) The viscosity is more stable over the extremes of temperature.
5) With the exception of some formulations used in external boots, silicone brake fluid is compatible with all standard brake components.
Drawbacks:
1) It's hard to pour without entraining air bubbles--hence an application will generally have a softer, spongier pedal feel.
2) It doesn't absorb water, so any water already in the system accu-mulates in the lowest point of the system and stays there, causing rust.
3) Glycol fluids begin to compress near their boiling points, whereas silicone fluids begin to compress at around 300-350 degrees Fahrenheit.
4) Additives in the fluid can vaporize at comparatively moderate temperature, increasing the spongy feel.
5) Silicone fluids expand significantly when hot.
6) Silicone fluid is functionally incompatible with systems that have held glycol-based fluids for any length of time, requiring flushing and seal replacement (there are counter opinions on this, which state that the modern silicone formulations are in fact compatible with only a flushing, rather than a complete reseal). The actual DOT specification requires chemical compatibility, so as far as that goes, the two fluids won't cause reactions if used in the same system, but they certainly won't mix, either.
7) It's pretty much incompatible with anti-lock brakes because the silicone fluids tend to be more viscous, which can cause problems with the timing of the pulses that are intended to work with the thinner glycol-base fluid. This sometimes leads to damage of the ABS valving. The rapid pulsing necessary to anti-lock functions tend to cavitate the fluid, as the tiny bubbles collapse and coalesce into larger ones, and then collapse and reform into smaller ones. This tends to counteract the ABS effect and can diminish the actual effective braking. This condition also heats the fluid and can lead to even more sponginess and possible damage to the ABS controller. Thirdly, silicone brake fluid tends to foam when expressed from a small orifice under pressure, reducing its hydraulic effectiveness greatly.
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Joined: May 2004
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From: NJ
interesting. i was in the auto store yesterday for my other car, and was looking at brake fluids...the valvoline synthetic says it is better for abs systems. is this, perhaps, not a silicone fluid?
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Joined: Sep 2002
Posts: 3,456
DOT 5.1 -- Non-Silicone Synthetic Brake Fluid
LONG LIFE 100% synthetic fluid for hydraulically actuated-brake and clutch systems. (Based on Polyglycol chemistry).
DOT 5.1 NON-SILICONE BASE suitable for up-grade from DOT 3 or DOT 4.
Fluidity specially designed for anti-locking brake systems (ABS).
Fully compatible and miscible with Conventional Brake Fluids.
This version is crystal clear and has extra solvency which has the ability to clean and put into suspension gum and sludge deposits formed by conventional brake fluids.
No special procedures are required when bleeding and replacing conventional system fluids with SynLube™ Stop-4-Life™ Brake Fluids.
Typical service life 60 months for DOT 5.1 Standard Formula
Thread Starter
Registered User
Joined: May 2004
Posts: 1,059
From: NJ
Registered User
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Posts: 3,456
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