Slow release
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From: Hammond, IN 46323
Slow release
I'm new to "Forum" but not to Fords. I've had them all my life. My 1998 f150 has a peculiar problem with the brakes insomuch as, while all the pads and shoes are new, the front brakes tend to keep braking a second or two even though I'm off the brake. I thought maybe pistons rusty and not releasing like they should, then I thought master cylinder. Anybody able to nail it down?
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From: Clayton,De
the pistons in the calipers i was told have a little o-ring that rolls with piston then when u let off it is suppossed to roll back with the piston it sounds like to me this is what is happening.
If it is just the front that would be my bet.
I am sure someone else could advise u how to fix this but all i know to do is pull the 2 off and put 2 new ones on.
If it is just the front that would be my bet.
I am sure someone else could advise u how to fix this but all i know to do is pull the 2 off and put 2 new ones on.
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From: Garland TX
You might get a better response posting this in the wheels, tires and brakes section. Have the brakes been replace recently? Calipers replaced rebuilt fluid flushed? Any history? It could also be a problem with the control valve.
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From: Hammond, IN 46323
Yes, as I said, I just replaced the pads in front and the drum brakes in the rear. I flushed the entire system and put in silicone brake fluid in the entire system. Fluid comes out clear and clean. You mentioned the control valve. Are you talking about the ABS system? If so, not only do I not know where it is, I have no idea how to service it. I was told it has to be calibrated by a dealer. True? Anyway, someone also mentioned the "O" ring on the pistons may need replacement. I'm still undecided how to proceed. If no other suggestions, I think I'll start with the piston cleaning and "O" ring replacement.
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At this point, your only real hope is to replace all the brake hoses and rebuild the calipers and cylinders (master and wheel) with new parts and flush the heck out of the lines.
an excerpt from a SuperChevy article I helped write:
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.
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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Junior Member
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From: Hammond, IN 46323
I'm afraid I miswrote my description of the brake fluid I used, but even so the information you gave is good to know. Thanks. Back to my brake fluid, it's not "silicone", its "synthetic". I'm not sure of what they synthesized, but its recommended for Dot 3 applications. I got pretty concerned when I read your answer, so I went back and checked the bottle and was relieved to see that it was not silicone. That now being the case, the brakes still hesitate before releasing. Back to square #1.
