Brake pulsation and replacing fluid

[steelerguy]

Originally Posted by curtis73

Rotors don't warp. It is the oldest and widest misconception in automotive history. They get depositions of abnormal material and the friction qualities are modified in certain parts of the rotor, but the runout you get is from load inconsistencies, not heat warping.

http://www.stoptech.com/whitepapers/...otors_myth.htm

You can temporarily solve the vibration by machining the rotors but if proper pad break in procedures aren't used it will come back very quickly, which is probably why SaturnSC2 had pulsating very soon.

Rust, pad material fusing, inconsistent pad application; all contribute to pulsating pedal, but make sure you attack the problem not the symptom.

Also, make sure you're diagnosing it right. In your post you say that the harder you press the pedal, the faster the pulsation. If that's the case, then it can't be a rotor issue since it would pulsate at the same speed the wheels turn regardless of how much you press the pedal.

Curtis,

Just scanning the attached article makes me think that I should be replacing the existing, still original brake fluid in my 1999 dodge Durango and doing it every year.

I have slotted & drilled front rotors on the way from JC Whitney (a product of Rotor Tech: www.rotor-tech.com) and was planning on replacing the existing pads with Autozone's lifetime carbon metallics & paying close attention to the break in procedures for both. I was considering getting the ceramic pads but I am under the impression that they actually generate more heat which is our biggest challenge here in Phoenix AZ. Have any thoughts on that? The Durango stops plenty quick with the existing carbon metallics but if there is wear or other good reason to go ceramic, I can do that. If you have a recommendation, a supply source would be great.

Thanks for any suggestions.

[curtis73]

I wouldn't worry about increased heat. Often times during a long, hard stop, brake temperatures will reach 1500 degrees or more, so the fact that its 110 degrees in Phoenix and only 90 degrees here in L.A. just doesn't make a real difference in brake pad temperature.

The ceramic pads sometimes make more heat, but their construction is such that it can handle it. The pads get much hotter than the rotors due to their size, so the ceramic pads will take a bit more heat. I wouldn't worry about it a bit. I have had mixed results with ceramic pads but in general I like them a lot. Go for it.

[steelerguy]

Originally Posted by curtis73

I wouldn't worry about increased heat. Often times during a long, hard stop, brake temperatures will reach 1500 degrees or more, so the fact that its 110 degrees in Phoenix and only 90 degrees here in L.A. just doesn't make a real difference in brake pad temperature.

The ceramic pads sometimes make more heat, but their construction is such that it can handle it. The pads get much hotter than the rotors due to their size, so the ceramic pads will take a bit more heat. I wouldn't worry about it a bit. I have had mixed results with ceramic pads but in general I like them a lot. Go for it.

Any warnings or recommendations on a kit for replacing the fluid? Have never done a complete system replacement but have read about it in the Haynes manual. Doesn't look too difficult.

[curtis73]

Nothing special. I like to siphon or soak out as much of the fluid from the mastercylinder as possible and put fresh in. Then you can bleed at each wheel until you get clear fluid.

[UncleBob]

(deleted to prevent from getting whined at again for posting to old threads)

[curtis73]

Aw. go ahead. I move the new posts to their own thread since it was a good question.

[steelerguy]

Originally Posted by curtis73

I wouldn't worry about increased heat. Often times during a long, hard stop, brake temperatures will reach 1500 degrees or more, so the fact that its 110 degrees in Phoenix and only 90 degrees here in L.A. just doesn't make a real difference in brake pad temperature.

The ceramic pads sometimes make more heat, but their construction is such that it can handle it. The pads get much hotter than the rotors due to their size, so the ceramic pads will take a bit more heat. I wouldn't worry about it a bit. I have had mixed results with ceramic pads but in general I like them a lot. Go for it.

Curtis,

Sorry to keep bothering you. BTW, replaced the front roders with Roto-Tech drilled & slotted rotors. Went with Friction Peformance Corp carbon metalic pads. Used your break-in method from that cool article. Still need to replace all the system fluid. All seems well when not experiencing the following rear brake fiasco.

Have you had bad luck with Autozone shoes & hardware?

Have a 99 Durango, 5.9 with 4wd. About 2 weeks ago, I changed my rear shoes & hardware, as well as the drums. I thought everything looked good. Bought the lifetime guaranteed & hardware kit from Autozone. Got Raybestos drums from JC Whitney.

Changed one side at a time & followed the Haynes manual exactly. The only thing that made me a little nervous was that the 2 top springs ended up being installed in a different order than the original installation. But this was exactly what the Haynes manual instructed & it was supported with a picture.

After a couple days, I started getting light shaking from the rear. It got progressively worse & could be be duplicated exactly by stopping or slowing the truck with the parking brake only. This means the problem is in the rear as that's all the parking brake actuates...right?

Anyway, I pulled the drums last night & saw that the rear rod on the passenger-side cylinder had slipped off & behind the 2-week old shoe & that was apparently causing my problem. No problem on the driver side.

I pulled the top 2 springs & manual adjuster. repositioned everything & reattached everything. Haven't done a ton of rear brakes, so I compared everything to the good side & all looked fine.

Put everything back together & test drove it...all light braking. I got 1 or 2 series of shaking, not quite as bad as before. Stopped it in reverse a couple of time & that made it even better. Thought that maybe the cylinder need reset after having the rod disconnected. Within 5 minutes there was no shaking & seemed to drive normally. Drove & stopped at 10-50 mph for 10 more minutes & it was like new.

Drove to work this morning & after about 10 miles (5 at highway speed) the bad shaking has returned. Apparently, one or more cylinder rods is off again.

Din't see any leaks from the cylinders. Did not check the cylinder mounting bolts (Doh!!!) but I've never heard of them coming loose on their own when they've never been changed.

I'm thinking of replacing the shoes & hardware (after checking the mounting bolts) with either Carquest or Napa parts. Thinking that the shoes on the passenger side were manufactured incorrectly or that the new springs or other new hardware are weak.

What do you think? Could I have done something wrong that causes the rod to come out away from the brake shoe? Did not think there was a lot you could do wrong & still get it to assemble & work for 10 or 15 miles.

[curtis73]

All I can think of to check is that you have the right adjustment cylinder on each side. I've switched them accidentally before and the reverse movement would actually loosen the adjustment.

Double check on who re-lines the shoes. Chances are the auto parts store name is just a stuffed box. If you go to any parts store and get the store brand, you might get shoes from any one of 10 manufacturers, so the the actual parts store where you buy the shoes has little impact.

also, are you making sure you are properly adjusting them? I like to push the cylinders back in the bores, mount the new hardware, screw the adjuster the whole way in, then put the drum on and spin it. Take the drum off and spin the star wheel out a few turns and keep doing in until you get a little drag. Not necessarily drag that makes it hard to turn, but the kind you can hear. That way you know you're getting contact. Then you can pump up the cylinders and the adjuster will be in the right spot to start working. Back up a few times and it should be spot on. If you still get your wobble and pulse after that, I'm not sure what to tell you.

You are right, though... the parking brake only actuates the rear shoes.

[steelerguy]

Originally Posted by curtis73

All I can think of to check is that you have the right adjustment cylinder on each side. I've switched them accidentally before and the reverse movement would actually loosen the adjustment.

Double check on who re-lines the shoes. Chances are the auto parts store name is just a stuffed box. If you go to any parts store and get the store brand, you might get shoes from any one of 10 manufacturers, so the the actual parts store where you buy the shoes has little impact.

also, are you making sure you are properly adjusting them? I like to push the cylinders back in the bores, mount the new hardware, screw the adjuster the whole way in, then put the drum on and spin it. Take the drum off and spin the star wheel out a few turns and keep doing in until you get a little drag. Not necessarily drag that makes it hard to turn, but the kind you can hear. That way you know you're getting contact. Then you can pump up the cylinders and the adjuster will be in the right spot to start working. Back up a few times and it should be spot on. If you still get your wobble and pulse after that, I'm not sure what to tell you.

You are right, though... the parking brake only actuates the rear shoes.

Chris,

This ended up being fixed by having the badly out-of-round brake drums machined by a local car shop: American Auto Lube & Repair at the SEC of Guadalupe & Cooper in Gilbert, AZ. 480-539-4086. They did the whole job for $43 & it took over an hour, including a test ride with me listening to me whine.

I know that I could probably taken the drums back to Checker where they were purchased 2 weeks before, but I did not trust them to get it right. They actually started this mess in the first place by screwing up my original equipment drum with a routine turn.

The drums I got from RockAuto.com were also bad. The owner at American Lube & Repair said that he would buy any critical parts at NAPA or CarQuest.

Stops on a dime with no shaking front or rear now.

[curtis73]

Excellent. Glad to hear it got fixed. Those must have been some seriously messed up drums