Uneven braking

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  #1  
Old 04-29-07, 01:09 PM
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Uneven braking

I have a '90 Mazda Miata. Well the other day when I was driving it, I noticed a drag when I released the accelerator. Felt like I had the parking brake on a little, but I didn't. Then it wouldn't go away and I started to get worried. So I pulled over and noticed the R/FRT brake ass'y was cookin' and I could smell burning brake disc. So I drove it home and manipulated the parking brake to get there. Well today when I disassembled it I could move the piston in and out of the cylinder easily...no stcking. So I put it all back together, took it for a ride and could not get the caliper to stick at all.
BUT, what I did notice (and I noticed this in the past) when I lock up all fours the back of the car tends to slide to the left. When I got home I touched the two front rotors and the R/FRT rotor was cooler than the one on the left.
I thought the calipers might need replacing, but now I'm not so sure. Could this be a problem with the distribution valve? Because one day it was sticking, but most of the time it won't clamp as hard as the left one? The brake pads are almost brand new, so it's not like the piston is over extended and cocked.
When I extended the piston manually I did not see any of the telltale pittings to the chrome surface.

Anyone have any idea what might be causing this type of inconsistency?

I almost bought it the other day when I had to lock 'em up on wet pavement to avoid an accident.

Thanx

Jim
 
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  #2  
Old 04-29-07, 02:55 PM
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I would start with a good bleed of the system. After the bleed, have your rotors check and turned if needed.

If after all this and the car is still having issues, it could be your valve or the caliper itself.
 
  #3  
Old 04-29-07, 03:21 PM
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mudduck

I don't even know if this type of vehical has rubber brake lines but I once had the same problems on a make of vehical and it was the brake line had broken inside. Creating a blockage where the brake fluid could not return to the resevoir.
 
  #4  
Old 04-29-07, 03:22 PM
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Flush

I would also start with a good power flush of the brake system replace all that old stuff with new fresh fluid.
 
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Old 04-29-07, 05:16 PM
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Hey, Thanx for all the advice!!!
The rotors are fairly new as the old ones were so worn and ugly looking. A flush and a bleed does sound like a good place to start. As far as the brake lines, they are metal except where they make the transition from the chassis to the wheel. At that point I guess you need some flexibility. But that seems to make sense too as I can remeber having similar problems with hydraulic hoses on heavy equipment.

Thanx again

Jim
 
  #6  
Old 04-30-07, 08:49 AM
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Originally Posted by michael van View Post
I would also start with a good power flush of the brake system replace all that old stuff with new fresh fluid.
How would you do a power flush?

Thanx
Jim
 
  #7  
Old 04-30-07, 10:54 AM
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couple of ways

A real power flush will require some equipment you can buy from a car parts store for about 50 bucks for a DIY application. Or you can have it done also or maybe a bit more at your local gararge. or you can do it the old fashiond way with two people one to push the brake and another under the car on bleeder screw duty.

Anyway start from the farthest wheel from the master cylinder and work your way in. (dont let fluid run low in master cylinder.) that is the job of the guy pushing the petal to keep it full.
 
  #8  
Old 04-30-07, 01:13 PM
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Thanx michael.
I'll start with that first.
Jim
 
  #9  
Old 05-01-07, 03:57 AM
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Cool uneven braking

When you said you disasembled, did you crack loose the brake line? Cause you might have let air in...Plus, it seems before your R/f was locked and now it wont work at all. I would check that brake line on that side.
 
  #10  
Old 05-01-07, 10:17 AM
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No, I didn't remove the brake line. I just worked the piston in and out manually with the line attached. I just removed the caliper from the wheel. The pads do engage the rotor, just not as much as the other side. Like I said after I put it all together and took it for a spin the r/frt rotor was hot, just not as hot as the left side. And I noticed this uneven braking months ago, especially on wet pavement.

After that brake had been dragging it did eventually ease up. After about a 1/2 hr. it wasn't dragging any more. But yes I did suspect the brake line may be the culprit.

I will flush the lines and see what kind of crud is in there. And also observe if any swelling of the line, where it makes the transition from chassis to wheel, occurs when pressure is applied to the brake.
 
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