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Fading brakes
Posted by: Acer
Date: June 29, 2020 05:15PM
My daughter, who has a good bit of experience driving, called me from a road trip. She was alarmed that suddenly her brakes faded and she barely stopped at a light. She had noticed no trouble before that. We had it towed. Naturally, the garage can’t reproduce the problem. What does the hive mind say?
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Re: Fading brakes
Posted by: btfc
Date: June 29, 2020 05:17PM
What car? Any big hills on her trip?
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Re: Fading brakes
Posted by: Acer
Date: June 29, 2020 05:21PM
Ancient Saturn. The are hills along the route, but this was in a stop and go four lane with modest grades.

Saturn is old, but very low miles. A cream puff literally owned by a little old lady who drove it but a few thousand miles a year. Lots of garage time.



Edited 1 time(s). Last edit at 06/29/2020 05:27PM by Acer.
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Re: Fading brakes
Posted by: btfc
Date: June 29, 2020 05:36PM
Maybe flush the brake system if it hasn’t been done in a while. Brakes getting too hot can be an issue therefore the hill question, and can also be caused by dragging brakes. And there’s always the master cylinder.
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Re: Fading brakes
Posted by: cbelt3
Date: June 29, 2020 05:37PM
Brake system leak. Vacuum leak someplace. A slow leak. Bleeding the line should get air, which is indicative of a leak. Probably a seal somewhere is slowly going bad. A cracked line will dump brake fluid like mad and is visible.
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Re: Fading brakes
Posted by: Acer
Date: June 29, 2020 05:43PM
Brake fluid reservoir was at max. FWIW
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Re: Fading brakes
Posted by: btfc
Date: June 29, 2020 05:44PM
Quote
cbelt3
Brake system leak. Vacuum leak someplace. A slow leak. Bleeding the line should get air, which is indicative of a leak. Probably a seal somewhere is slowly going bad. A cracked line will dump brake fluid like mad and is visible.

All good things to troubleshoot, but I would think that the shop would be on top of them. Of course...

Vacuum leak/ brake booster might be a possibility.



Edited 1 time(s). Last edit at 06/29/2020 05:46PM by btfc.
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Re: Fading brakes
Posted by: modelamac
Date: June 29, 2020 05:54PM
Quote
Acer
My daughter, who has a good bit of experience driving, called me from a road trip. She was alarmed that suddenly her brakes faded and she barely stopped at a light. She had noticed no trouble before that. We had it towed. Naturally, the garage can’t reproduce the problem. What does the hive mind say?

I think cbelt3 nailed it. The fading is probably due to slow leak in vacuum-assist(booster) or vacuum line that "charges" it. It is the only thing that fits the symptoms, IMHO.



Told my wife I wanted to be cremated.
She made me an appointment for Tuesday.
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Re: Fading brakes
Posted by: C(-)ris
Date: June 29, 2020 06:33PM
Is she positive that she didn't have the edge of her foot on the gas pedal pressing down on both?



C(-)ris
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Re: Fading brakes
Posted by: space-time
Date: June 29, 2020 06:33PM
in cases like this, is it better to pump the brakes or press and hold?

I'd guess by panic I would probably pump, but I am not sure if that is the best option.

Thanks
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Re: Fading brakes
Posted by: JoeH
Date: June 29, 2020 06:44PM
Leaking vacuum booster or line to it, better to press and hold. Releasing my lose what assist the vacuum is providing.

Leak within the master cylinder, pump.
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Re: Fading brakes
Posted by: space-time
Date: June 29, 2020 08:24PM
Quote
JoeH
Leaking vacuum booster or line to it, better to press and hold. Releasing my lose what assist the vacuum is providing.

Leak within the master cylinder, pump.

so you don't really know, you need to try and see what "sticks"
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Re: Fading brakes
Posted by: macphanatic
Date: June 29, 2020 08:24PM
Leak with master cylinder or air in the system. Has the brake system ever been completely flushed? Brake fluid absorbs water over time regardless of mileage. I would start there.

A vacuum leak shouldn’t result in spongy brakes. It would result in brakes that require a lot of effort to apply.
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Re: Fading brakes
Posted by: NewtonMP2100
Date: June 29, 2020 08:38PM
.....brake.....me off a piece of that.....????



_____________________________________

I reject your reality and substitute my own!
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Re: Fading brakes
Posted by: mrbigstuff
Date: June 29, 2020 08:47PM
could be any of those things, but also a failed piston on the caliper which is not really bad, and would mean replacing the caliper with a remanufactured caliper.
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Re: Fading brakes
Posted by: deckeda
Date: June 29, 2020 08:49PM
With no leaks and no repeatable error, take the car back and continue to monitor -- carefully.

The shop should know this, but for fading pedal you press and hold. It should basically stay there forever unless there's and internal or external leak. But press really hard and you can always get the pedal to do "something."

A few years ago I replaced front lines, calipers, rotors ... thought I had air in the line somewhere because the pedal seemed softer than I'd remembered. Even slowly seemed to go towards the floor. I re-bled everything etc. Began to drive it and realized it was the same as it ever was, no worse.
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Re: Fading brakes
Posted by: cbelt3
Date: June 29, 2020 09:10PM
FWIW train your daughter in brake system failure processes.
1- situation awareness and attempt maneuvering to avoid an accident.
2- Alert (flashers / horn)
3- let go the accelerator and downshift
4- emergency brake
5- maneuver off the road.

You have to practice to be able to do all this at the same time. Driving a beater gives you a great set of skills !
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Re: Fading brakes
Posted by: macphanatic
Date: June 29, 2020 09:13PM
Another thought - the brake hoses may be soft.
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Re: Fading brakes
Posted by: RAMd®d
Date: June 29, 2020 10:54PM
First, find out the symptoms of the failure.

Are the brakes in fact fading?

That means different things to different people.

To me and the car guys I know, fading means reduced stopping distance for the same pedal pressure and feel.

When this happened, what did the pedal feel like to her?

Did it go soft or fall to the floor board?

You said she has a lot of driving experience, so I won't presume what you need to tell her.

But telling the shop exactly what occurred should help them fix the problem.

Unfortunately, without being able to reduce the problem, it may come done to RTT - Replace This and That.

Or time to try another shop.




When a good man is hurt,
all who would be called good
must suffer with him.

You and I have memories longer than the road that stretches out ahead.

There is no safety for honest men except
by believing all possible evil of evil men.

We don’t do focus groups. They just ensure that you don’t offend anyone, and produce bland inoffensive products. —Sir Jonathan Ive

Perfection is the enemy of progress. -Winston Churchill

-An armed society is a polite society.
And hope is a lousy defense.

You make me pull, I'll put you down.

Mister, that's a ten-gallon hat on a twenty-gallon head.

I *love* SIGs. It's Glocks I hate.
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Re: Fading brakes
Posted by: Acer
Date: June 29, 2020 11:13PM
The car is in another town. She was on the first leg of a 600 mile weekend, so we didn't take chances, we left it there, I brought her home, she took my car. I'll bring the car home, IF I know I can do it safely. Tooling around the parking lot after sitting a bit, the brake seemed to work again. In my estimation, the brake petal had a lot of give to it, it was very easy to press it all the way to the floor. But, I wasn't going to truly test drive it on the open road until a mechanic looked at it. Perhaps I'm a bit paranoid, but last summer my son's car had bad brake lines that almost put him in the creek.
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Re: Fading brakes
Posted by: cbelt3
Date: June 29, 2020 11:42PM
Acer ... be safe...
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Re: Fading brakes
Posted by: Racer X
Date: June 30, 2020 03:31AM
Brake fade is when the brakes are so hot, they become less effective and stopping distance increases. Sometimes it is because the fluid has absorbed water, which lowers the boiling point, and it essentially boils in the hot calipers or wheel cylinders. Or the pads/shoes are thin, maybe not worn out, but get so hot they don't grip as well as they should. Or the drums/rotors are thin, but not even worn out, and overheat too easily. Or all of the above. Happened on my partner's V-8 Mountaineer with towing package in the Colorado Rockies 5 years ago. We stopped and had a soda, and they were better. Then about halfway down the pass we stopped in Ouray and did some window shopping. They were fine again. Truck was crammed full and heavy. Even with the oversized brakes from the towing package they were taxed. When we got home new pads and rotors up front, and pads in the rear. Got even heavier duty ones. Never had a problem since.

Really common on old 4 wheel drum musclecars or pick-ups. That's why the full sized Buicks had huge finned aluminum brake drums with iron inserts for the wear surface. The finned aluminum shed the heat quickly. Modern vehicles have what I would say are undersized brakes. Or sized as small as possible and still be safe under normal conditions. There isn't much safety factor built in anymore.

Falling pedal isn't brake fade. Spongy pedal isn't normally brake fade. They work fine again when cold is a good indicator.



********************************************
The police have no duty to respond. See Castle Rock v. Gonzales, 545 U.S. 748 (2005) or Warren v. District of Columbia[1] (444 A.2d. 1, D.C. Ct. of Ap. 1981)



Edited 1 time(s). Last edit at 06/30/2020 03:36AM by Racer X.
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Re: Fading brakes
Posted by: RAMd®d
Date: June 30, 2020 07:01AM
Brake fade is when the brakes are so hot, they become less effective and stopping distance increases...

Falling pedal isn't brake fade. Spongy pedal isn't normally brake fade. They work fine again when cold is a good indicator.



This, and all the stuff in between.




When a good man is hurt,
all who would be called good
must suffer with him.

You and I have memories longer than the road that stretches out ahead.

There is no safety for honest men except
by believing all possible evil of evil men.

We don’t do focus groups. They just ensure that you don’t offend anyone, and produce bland inoffensive products. —Sir Jonathan Ive

Perfection is the enemy of progress. -Winston Churchill

-An armed society is a polite society.
And hope is a lousy defense.

You make me pull, I'll put you down.

Mister, that's a ten-gallon hat on a twenty-gallon head.

I *love* SIGs. It's Glocks I hate.
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Re: Fading brakes
Posted by: macphanatic
Date: June 30, 2020 07:53AM
If you have no record of the brake system being flushed, why not have it done before driving home? Brake fluid should be completely flushed every few years.
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Re: Fading brakes
Posted by: Acer
Date: June 30, 2020 08:55AM
Yes, that is the question...what's the least I should do. Change of brake fluid sounds reasonable.
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Re: Fading brakes
Posted by: Racer X
Date: June 30, 2020 10:16AM
Most brake fluid is hygroscopic. It goes out of its way to absorb moisture. That's one of the reasons they went to plastic reservoirs. You do not need to open to see fluid level or relative fluid color.

And the aluminum brake components do corrode, like the iron stuff did/does. It's chloride corrosion, and it still pits low spots in the system, or wheel cylinders and calipers, or the piston bore in the master cylinder.



********************************************
The police have no duty to respond. See Castle Rock v. Gonzales, 545 U.S. 748 (2005) or Warren v. District of Columbia[1] (444 A.2d. 1, D.C. Ct. of Ap. 1981)
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Re: Fading brakes
Posted by: Acer
Date: June 30, 2020 11:47AM
I am having them flush the fluid, then we'll bring it home, monitor and adjust. We'll review usage of the emergency brake.
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Re: Fading brakes
Posted by: mrbigstuff
Date: June 30, 2020 12:15PM
my money is still on the caliper pistons being shot. actually, you just buy the whole thing rebuilt now, unless you are a glutton for punishment.
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Re: Fading brakes
Posted by: NewtonMP2100
Date: June 30, 2020 12:56PM
....what about fading.......looks......??



_____________________________________

I reject your reality and substitute my own!
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Re: Fading brakes
Posted by: lost in space
Date: June 30, 2020 01:02PM
What RacerX said. Fading is when the brakes get so hot they can't dissipate the heat from the friction of the pads against the rotors. To be effective, the brakes have to be able to dissipate heat at a higher rate than the rate of heat generated from friction.



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Re: Fading brakes
Posted by: NewtonMP2100
Date: June 30, 2020 01:05PM
.....super models have the same problem......



_____________________________________

I reject your reality and substitute my own!
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Re: Fading brakes
Posted by: RAMd®d
Date: June 30, 2020 01:43PM
So now everybody knows what brake fade is.

The question is still – what were the symptoms?

Soft pedal?

Hard pedal?

Pedal go to the floor?

If so, could it be pumped up?

Regular pedal feel, but little stopping power (brake fade)?

Knowing exactly what symptoms goes far to diagnosing the problem.

Otherwise it's just a bad game of Pin the Tail.




When a good man is hurt,
all who would be called good
must suffer with him.

You and I have memories longer than the road that stretches out ahead.

There is no safety for honest men except
by believing all possible evil of evil men.

We don’t do focus groups. They just ensure that you don’t offend anyone, and produce bland inoffensive products. —Sir Jonathan Ive

Perfection is the enemy of progress. -Winston Churchill

-An armed society is a polite society.
And hope is a lousy defense.

You make me pull, I'll put you down.

Mister, that's a ten-gallon hat on a twenty-gallon head.

I *love* SIGs. It's Glocks I hate.
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Re: Fading brakes
Posted by: Racer X
Date: June 30, 2020 01:44PM
Just a FYI, not specific to this car... Ford and others went to phenolic plastic for caliper pistons so that they wouldn't transmit the heat directly from the pads, through the piston, and boil the brake fluid. In severe duty use, they still used steel though, like police vehicles and HD brakes on the heavier pickups.



********************************************
The police have no duty to respond. See Castle Rock v. Gonzales, 545 U.S. 748 (2005) or Warren v. District of Columbia[1] (444 A.2d. 1, D.C. Ct. of Ap. 1981)
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Re: Fading brakes
Posted by: Acer
Date: June 30, 2020 02:02PM
The braking was not severe in this scenario. Hills on the way, but not steep hills with stops at the bottom.There were stoplights, but spread out with nearly a mile between some, and traffic was not heavy stop-and-go.
She describes it as everything was normal, then suddenly, she had to put the pedal to the floor and clinch buttocks to stop.
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Re: Fading brakes
Posted by: mrbigstuff
Date: June 30, 2020 03:14PM
If that's the case (sudden failure), I'll retract my response and agree that it sounds more like the fluid found a way out. Also probably not fade or heat of it happened that dramatically.
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Re: Fading brakes
Posted by: Racer X
Date: June 30, 2020 03:50PM
Yeah, sounds like major leak, or internal seal failure in the master cylinder.



********************************************
The police have no duty to respond. See Castle Rock v. Gonzales, 545 U.S. 748 (2005) or Warren v. District of Columbia[1] (444 A.2d. 1, D.C. Ct. of Ap. 1981)
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Re: Fading brakes
Posted by: mrbigstuff
Date: June 30, 2020 05:26PM
Quote
Racer X
Yeah, sounds like major leak, or internal seal failure in the master cylinder.

yeah, that, too
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Re: Fading brakes
Posted by: macphanatic
Date: June 30, 2020 05:52PM
I wonder if fluid didn't leak into the brake booster. The puzzling part is that someone would have noticed a fluid drop from the master cylinder if there was any fluid leakage. That's what makes me wonder if the brake hoses have softened and are expanding under pressure.

I'd be real curious to see the condition of the fluid.
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Re: Fading brakes
Posted by: Racer X
Date: June 30, 2020 08:07PM
Quote
macphanatic
I wonder if fluid didn't leak into the brake booster. The puzzling part is that someone would have noticed a fluid drop from the master cylinder if there was any fluid leakage. That's what makes me wonder if the brake hoses have softened and are expanding under pressure.

I'd be real curious to see the condition of the fluid.

Sometimes the outer layer in a brake hose can crack, and the steel braid inside will rust, allowing a portion of the hose to balloon under pressure, but not burst. Internal leak in the master cylinder seals can bleed off pressure, but not leak externally. Usually corrosion in the bore that chews up the seals' edge, letting fluid to leak past to the other side, but kept internal by the end seals.

I try to go in depth about a subject in general, beyond the original narrow focus question, to educate and hopefully answer others' questions along the way. I have broken, and fixed a lot of stuff, and when running the auto parts store, I dissected quite a few cores to find out the failure.

I have seen water pumps where the impeller was corroded away to a gnarly hub and then the shaft, and the aluminum body was barely holding water. Starters without teeth, and starter solenoids welded closed, fused alternator diode trios. Some crazy stuff.

On my GSX, the original passenger front brake hose had cracks in the rubber. When vibration from the stiff suspension and @#$%& roads caused a battery case leak, the acid got into the steel braid in the brake hose. Hose ballooned when braking, but looked "fine" when inspected. That resulted in a LOT of work, Just gutted the brakes to be safe. Then I have a starting point.



********************************************
The police have no duty to respond. See Castle Rock v. Gonzales, 545 U.S. 748 (2005) or Warren v. District of Columbia[1] (444 A.2d. 1, D.C. Ct. of Ap. 1981)



Edited 1 time(s). Last edit at 07/01/2020 08:29AM by Racer X.
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