Brakes from Hell!

[tripletdaddy]

Oh, btw, how did the brake fluid get so hot on the track? Was that from using the brakes? Or, do they do that on their own? That doesn't sound like a good way to test you brakes.

[shorod]

I suspect it was from hard braking from 130 mph with 2 people in the car, 4-piston aluminum calipers in the front and single piston calipers in the rear, all clamping hard to make the nearly 90-degree turn coming up in a hurry.

After the fluid cooled the brakes came back and I was able to drive it home. No issues during normal highway driving, and no further issues once I went to the Valvoline SynPower, even at the track. I later installed braided stainless brake hoses which made a surprisingly big difference.

-Rod

[tripletdaddy]

Interesting braking system. I'm not familiar with hydraulic braking systems that include some sort of cooler, but I would think it would be necessary in some situations. I'd think that race cars may need that based on your experience. I'm not surprised the braided brake hoses helped reduce the heat in the brake fluid as it works as a good conductor of heat and easily looses it with the small wires, whereas black rubber hoses are really terrible conductors of heat because of thermal resistance and it's a black body, which like to absorb heat.

[shorod]

There wasn't a cooler, other than the large aluminum calipers. I just didn't take the car on the track any more that afternoon, so by the time I was ready to drive home, the fluid was cool and functional again. Maybe I boiled all the moisture out too.

The main benefit of the braided stainless brake hoses is the stainless steel braid keeps the hoses from expanding under braking. On a typical rubber hose, some of the fluid force causes the diameter of the brake hose to expand slightly. The theory of the braid is to reduce that expansion so there is a more efficient transfer of pressure to the brake calipers.

-Rod

[tripletdaddy]

I wasn't implying you did have a brake fluid cooler, but just thinking how that might be needed in some scenarios, maybe high speed racing? I don't know. The heat alone certainly could make those rubber hoses expand, then make them mushy, add some pressure, then more heat, and on and on... not good. SS braid sheath makes a lot of sense for that problem. I was just thinking of the added benefit of the cooling the braids could provide as a byproduct of its design, not necessarily a primary design criteria. Though, I wouldn't be surprised if the designers were aware of that attribute when considering using the wire sheath.

[shorod]

To keep the braid from fraying and collecting junk, they cables had a vinyl (or similar) clear coating over them which would reduce any heat transfer benefit from the braid. But they looked "cool" (no pun intended).

-Rod

[RaeRae1]

Originally Posted by TaurusKing

Do they fail as you're applying the pedal slow, as in an extended braking situation??? What happens when you apply the pedal quickly??? Try both in an empty parking lot, any difference??? I had a car long time ago where the pedal would sink to the floor in a situation such as extended braking down a hill with a stop sign at the bottom, but operate flawlessly otherwise.. master cylinder seals were bad, would only leak in above type deal, long application of pedal..

It sounds like you have pretty much replaced most of the areas that would cause this issue. I would suspect air in the lines would cause the pedal to be "soft" but not result in it going directly to the floor unless the air pocket was right at the MC. If there were air in only one line I don't think the pedal would go all the way. Try holding the brake down hard for a couple of minutes and see if the pedal slowly starts to sink. If the seals on the MC are bad it should show by allowing the fluid to drain back into the master cylinder instead of holding pressure.

[tripletdaddy]

To add to RaeRae1's thoughts, if there is some sort of air and/or seal issue right at the MC, wouldn't air bubbles or a small amount of foaming possibly show up in the reservoir? You haven't said if you are loosing fluid or not, which would be consistent with the pedal going to the floor. If so, then you need to find the leak. I think it's been suggested already to check the brake cylinders if no other leaks are found. Have you checked your brake hoses for softness, sponginess, abnormal condition?

Now on those braided brake lines, what a waste of good heat transfer.....another case of form winning over function...tsk,tsk....oh well. : Fraying? Eh. Collect junk? Ok. Cool and sleek vinyl coating sounds good, too....

[Hungrycat7]

The car is not losing any fluid! I have checked the lines and all looks normal. I am pretty much convinced it is the binding caliper. Just started a new job so as soon as I get a chance I am just going to throw a new caliper on and hopefully be done with it. I think the fluid is just getting too hot!

[mechhound]

99% it's the master cylinder. There are two cups in the master cylinder, one for the front brakes and one for the rear brakes, in a straight line ie one in front of the other, fluid gets past the first cup allowing the brake pedal to sink with no external loss of brake fluid. Why doesn't the brake pedal go to the floor every time the brakes are applied? I haven't figured that out. Not only have I experienced this myself and replacing the master cylinder fixed the problem, I have read of this on other forums like this, and yes replacing the master cylinder fixed the problem.