How long does brake fade last?

sizemoremk

Registered User
Or is this even bake fade???

OK, so I was out beating on the SC a bit, and done some pretty aggressive speed up, and and brakins'.

Just before I pulled into the neighborhood, the brakes kinda went away a bit, so I went exactly 1 more mile at a slow roll, about 20MPH, and I still seem to have had "brake fade" if this is indeed what it was. So does it take them awhile to cool down again?

I did check the fittings on all the calipers (as I did the 99 mustang PBR swap in the front), as well as all the plumbing I did for line lock and non-abs conversion, etc. Everything seemed dry, and the level is still good, so I don't appear to have lost any fluid...

I guess I just wanted to make sure this is at least semi normal when beating heavily on the car.... Like I said, there was several 45-50 rolls to 80-90 ad back down agains as I was loggin some data...

Thanks guys!
 
Brake fade is a condition that occurs when the pads get so hot, they start to cause a boiling effect with the metal and the gasses produced from the heat of the friction. The other cause is when the caliper piston (pistons in your case) heat up and cause the fluid to boil. If you did a swap, I would be willing to bet you bled your brakes. This would mean that there is new fluid in the caliper. In the first instance, you should have brakes as soon as the rotor is not glowing anymore. Ok...maybe not glowing with a set of street pads but pert near glowing. The second instance, you would have brakes as soon as they cool down BUT you will have a spongy pedal. I would be willing to bet, you busted an o-ring or seal inside your master cyl. See if you can "pump up" your brakes. If you can...you and I are in the same boat.

NOW...how much of a difference did the PBR setup make?

Chris
 
I'm actually unimpressed with the PBR setup, but I did the swap at the same time as the non-abs setup and have been making djustments ot the pushrod to get the pedal right. I believe that the pushrod can come out a hair more, I just need to adjust it again. Initially the crown vic rod was not long enough, so I had to get a bolt and round off the head to replace it.

Now it did seem like I had brake fade a time or two at some quick deceleration a time or two before, like down from 100 MPH, so now I'm curious if I'm just not getting full travel, which would increase heat.

I guess I'll have to check it in the morning to see if it still has fade... If it is a seal in the MC, will that come and go, or would it remain constant?
 
There is no set rule that o-rings have to follow. My MC is failing. I can pump it up 4 or 5 times and really crank on it. But if I step on it once, it just is....limp feeling. It can lock them up...but the pedal is too close to the floor for me.

Chris
 
Another MC test is step on the brake pedal, then let up a little, then apply pressure again. If it sinks on the second application it is bypassing the MC bypass therefore bad master.
 
Ok Chris, I rechecked things and re-bled the brakes, and still the brakes are not all there.

So I loosened up the MC to see if I could adjust the pushrod, and sure enough, it looked rusty back there, and looks like fluid had dripped down the booster where the MC bolts up... So I assume when a seal goes, the fluid comes out the back of the MC??

Oh, I just found this, kinda interesting!
http://www.popularmechanics.com/automotive/sub_care_clinic/1271851.html?page=1&c=y

Thanks bru'
 
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That makes sence...I have never thought of it that way, but I have seen that connection before. Guess I am just slow:cool:. Lemme know what it feels like as far as stoppin goes when you git er done.

Chris
 
This problem is still pissin me off, I believe some of the problem is still brake fade. Maybe because the pedal is not grabbing hard enough to stop, so it is just spinning, and creating too much friction, compounding the problem. Its hard to explain, but it really seems like the brake components are working right, however it is just shy of the capacity to stop the car. Like it needs 10%-15% more stopping power. I am aware this isn’t the case, just having trouble putting the symptoms into words.

I went ahead and replaced the master cylinder, and "bench bled" the new using the pedal while bolted to the booster but using the supplied plastic fittings and tubes, etc. Took several pumps but I’m 100% sure there was no air in the MC when I was done. To bleed, I go furthest to the MC, and did it twice (as in to rounds) for each corner. I use a coke bottle with some fluid in the bottom, with clear tubing coming through a hole in the cap, this tube fits snuggly to the brake bleeder. I can then open the bleeder and pump several times until clear fluid comes through with no bubbles whatsoever. Just thought I’d throw all that in just so I don’t get asked about are they bled correctly.

Ok! If I get the car to 60-70, and try and slow it quickly, the brakes become significantly (or scary) less responsive. They seem to go 90% to the floor “under power” (or feeling right and slowing the car properly) but the last 10% of travel seems hard, like it reaches a mechanical stop, but hasn’t stopped the car yet. This has me wondering if its a booster problem, because at low speed, if I apply lots more pressure (for that last 10%), I can make them lock up; but at higher speed, it brings on significant “brake fade” really quickly, and it will take a mile or so of light cruise (with very little brakes) before the brakes “come back” enough to make me even semi comfortable to drive slowly back to the house… And then if I let it sit for 15-30 minutes or so, they seem to act OK again, at least at low speed. I aint driving it right now just in case, but it does seem like it would drive fine in the traffic, unless I had to stop or brake aggressively on the interstate… just to further describe the problem.

I was originally concerned that there was leaking out of the rear of the MC between the MC and the Booster, as there was a few drips where they bolt together; but it really didn’t smell like brake fluid once I got it out, it was more like grime back there, so I am curious if it is more likely that there was some grease leaking out form the booster where the pushrod comes out although it doesn’t look like there is a seal of any kind in that area, it could have be leaking from?

So I’m at a loss now. Since I’ve done the swap (non-abs + mustang PBR calipers) the car seems to have stopped fine, just not very impressively. So the way it is acting is kind of “all of a sudden” though I believe there was a slight hint that it wasn’t acting 100% right when I first did the conversion to begin with.

Could the booster be bad? Could one of the rubber lines be failing, and “swelling” rather than delivering all fluid to the wheels (I would think it would have to be both sides if this was the case???) Or is there some air trapped in the calipers themselves???

I believe the pushrod length to be correct, I did have to use a screw with the head ground down to replace the original pushrod, as the original was allowing pedal movement before the pushrod really engaged the MC piston. As of now, the brakes do immediately respond, and there appears to be no slack in the pedal before the car begins to stop…

I don’t know what to do next…
 
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