Low braking force

[maydog]

Hello,

I got a chance to take my wife's 96 aurora for a spin today and notices that the brakes feel weak. They respond quickly to a tap of the pedal but lack enough force to even lock up the tires.

I pulled the tires off to inspect the pads, both front and back have adequate material. The fluid resivor is full, I bled the brake lines this summer.

The pedal does not feel soft, I can step on the pedal very hard and it will slowly go to the floor while the vehilce slows layizly to a stop.

I was going to change the fron pads, but it appears that I do not have the right size allen wrench - can anyone tell me the size?

I am leaving the car garaged until I can fix this problem. The current theories I am contemplating are:

1. Glaze on the rotors and pads - what does this look like, how do I identify it?

2. Poor pumping performance from the master cylinder

3. Vacuum leak in brake booster

4. Failing brake lines

Has anyone ever experienced something like this? I do not have much experience with the brake system other than changing pads and bleeding the lines. If I cannot find the source, I will have to send it to a dealership (yikes!)

Thanks,

md

[Ranger]

Sounds like the master cylinder needs to be replaced if the pedal goes to the floor and there are no leaks.

[Ed Fenwick]

Aloha Maydog,

I have the same thing with my wife's Jeep after the ABS pump was replaced. Her's will pump up some, so I think that there is still some air in the lines. Will yours pump up, or just go to the floor? I guess that it is hard to bleed an ABS system? Ed

[maydog]

The brake pedal is firm, I can only press it to the floor with a lot of force. It feels about as firm or more so than my STS, except my sts is able to porvide enough stopping force that the ABS will come on.

I would expect that if air was in the lines the pedal would feel squishy, right?

Anyone know of any simple tests to diagnose the problem, I do not want to start throwing parts at it yet?

Also, anyone have that allen wrench size for the fron calipers?

Regards

[JasonA]

1. Glaze on the rotors and pads - what does this look like, how do I identify it?

Has anyone ever experienced something like this? I do not have much experience with the brake system other than changing pads and bleeding the lines. If I cannot find the source, I will have to send it to a dealership (yikes!)

Yes, twice. I replaced the brakes on my wife's '97 Saturn with China rotors and AC-Delco pads. I used brake cleaner on the rotors, and installed everything. The braking was weak. The pedal was firm, but the braking was weak. I took the pads back off, scuffed them GOOD with sandpaper and reinstalled them and it proceded to put me through the windshield on a hard stop. Definite improvement.

I say twice because I think the pads on my Seville are glazed. I guess I can't complain that it doesn't lock the tires, but even on wet pavement, the ABS rarely applies in hard stops. I'm thinking about taking the pads off, having the rotors cut, and scuffing the pads. Then again, they may be old enough to warrant putting new pads on. They have over 50,000 miles on them. They're Bendix HD. Lasted great. Stopping power was always a touch off though. I'd say a 6/10, whereas the Delcos that were on there were closer to 8/10.

[jhall]

maydog,

A quick check on the master cylinder is to shut off the car and tap the brake pedal a few times to lose the vacuum in the booster.

When the pedal gets really stiff, push it down. If the pedal continues to move toward the floor, you've got a bad master cylinder.

Good luck!

[maydog]

Those are good suggestions - thanks.

I had though about roughing up the pads but didn't want to mess anything up. I guess it is an okay thing to do.

I will try the check on the master cylinder. However, I think that I can push the pedal all the way to the floor on my sts as well (with a hard push). Maybe my legs are just freakishly strong from all my bicycling. I had figured that the brake had some spring loaded mechanism to prevent snapping of the pedal arm.

I will check again.

[CadiKing]

1. Glaze on the rotors and pads - what does this look like, how do I identify it?

Has anyone ever experienced something like this? I do not have much experience with the brake system other than changing pads and bleeding the lines. If I cannot find the source, I will have to send it to a dealership (yikes!)

Yes, twice. I replaced the brakes on my wife's '97 Saturn with China rotors and AC-Delco pads. I used brake cleaner on the rotors, and installed everything. The braking was weak. The pedal was firm, but the braking was weak. I took the pads back off, scuffed them GOOD with sandpaper and reinstalled them and it proceded to put me through the windshield on a hard stop. Definite improvement.

I say twice because I think the pads on my Seville are glazed. I guess I can't complain that it doesn't lock the tires, but even on wet pavement, the ABS rarely applies in hard stops. I'm thinking about taking the pads off, having the rotors cut, and scuffing the pads. Then again, they may be old enough to warrant putting new pads on. They have over 50,000 miles on them. They're Bendix HD. Lasted great. Stopping power was always a touch off though. I'd say a 6/10, whereas the Delcos that were on there were closer to 8/10.

jadcock,

Am I confused, or did you put cross drilled / plated rotors on your caddy?

I am about to change out the rotors, etc, and wondered how

your rotors were for the long run.

thanks,

[JasonA]

Am I confused, or did you put cross drilled / plated rotors on your caddy?

I am about to change out the rotors, etc, and wondered how

your rotors were for the long run.

Yes, I put cross-drilled. I'm going to correct myself -- it's been over 55,000 miles on the pads and rotors and it still stops completely fade-free. The Bendix HD pads are more of a long-life type pad, so I expected them not to be as grabby as maybe some other brands. I do think that scuffing them up might help. Either way, braking performance is still 100% sufficient. Just not race-car tight.

But none of that has to do (I don't think) with the rotors themselves. The Powerstop rotors are radiused on the holes and so far, after 55,000 miles, mine haven't cracked a bit. That was the best 350 bucks I've put on this car. Whenever our Grand Caravan needs front rotors, I'll look and see if Powerstop has rotors for that application.

[Ranger]

Maydog,

I think if you reealy try hard, you may be able to press the pedal to the floor but if under normal pressure is slowly sinks to the floor as your first post led me to believe, then it's a master cylinder. If you and apply normal pressure and the pedal holds, then I think it is normal. If, however, you can raise the pedal height by pumping it up, then there is air in the lines that need to be bled out.

[maydog]

thanks all for the tips, I got the right size hex tool tonight and removed the front calipers. The outside pad had adequate material, but the inside pad on the driver side was worn nearly away. The pedal felt firmer right away after putting in the new pads.

I couldnt take the car out for a test drive yet as some epoxy putty on the radiator (another thread coming soon) is curing. I will bed the new pads tomorrow and give an update.

md

[adallak]

The outside pad had adequate material, but the inside pad on the driver side was worn nearly away.

Did you find out the cause? A frozen caliper, bad caliper pins/ bushings?

[Ranger]

I've had that happen before as well. As Adallak said, find the cause. I'd bet on a dried out pin. Had that happen on my daughters car a couple of years ago. Cost a second set of pads because I neglected to check it the first time. When I found it, it was rusted badly. I wire wheeled it and siliconed it good and that was the end of it.

[maydog]

Well after a little beating on the back roads the brakes grab like they are supposed to again. I do not really know what happened to the pad. The pins seem to have good movement. He alignment is off some, I wonder it that could be doing it.

Thanks for the help, I learned some simple tests and enhancements for braking.

md

[blunted]

Edit: whoops wrong thread.