pulsating brake

[duspan]

i have a 03 2500 with 36000 miles on it,i wanted to change the front brakes over to EBC brakes,the rotors looked fine. after i i did the swap i started getting a pulsation in the petal?? i went and bought new rotors also pads, but still have the pulsation???



thank-you

gary

 

[jelag]

Your 3 line question leaves a lot of information left out for someone to really help... ... but here is a start... .

When a rotor is over heated it can cause brake pedal pulsation. The overheating process causes it to warp and thus not run true to the center line of the bearings... . Once this occurs the rotor is trued and all is well...

When a new set of pads are installed, and the calipers are not inspected correctly, one caliper might be dragging and this will cause the same problem... . the rotor overheats and warps...

When the boot between the piston and caliper is damaged, dirt will get behind the boot into the piston and will not allow the piston to return correctly... . this slight drag can and will cause that rotor to over heat and cause it to warp... .

Also, some new rotors are shipped without bearing races in them, and if the bearing race is not seated correctly and out of true condition can result...

In addition, all rotors should be trued up, even when new after new races are installed... the CNC equipment used to manufacture a rotor might not be spot on, thus allowing the rotor to be out of true...

I'd almost bet that you pushed the piston back when you installed new pads instead of bleeding the dirty brake fluid out of the system... and sometimes this dirt can cause the piston to not return correctly... this dirt gets between the seal, piston and bore of the caliper, and pressure will push the piston out but once your foot is off the pedal the quick return of fluid sort of pulls back the piston just a fraction of an inch and it no longer touches the pad, thus the brakes are free... . one piston is dragging in the bore overheating one rotor...

Last, severe damage can be caused by this dirt pushed back into the master cylinder... .

So to really help let me ask these questions... .

1 - We're the first set of factory pads worn out? if so, how, if not why were they replaced?

2 - did you bleed off the dirty brake fluid when you compressed the pistons?

3 - did you inspect the boots that cover the piston and caliper for damage from heat, or dirt, or just being not seated in the bore?

4 - Why did you replace the pads the second time? The first set should have been fine!!

5 - were there races in the new rotors, and if not, why did you not turn them?

 

[B.G. Smith]

i have a 03 2500 with 36000 miles on it,i wanted to change the front brakes over to EBC brakes,the rotors looked fine. after i i did the swap i started getting a pulsation in the petal?? i went and bought new rotors also pads, but still have the pulsation???



thank-you

gary

The rotors just slip off the studs on these don't they? It sounds like something is behind one of the rotors causing it to run out of true. If you have a dial indicator, remove the wheel and pry the pads back a hair so you can rotate the rotor and check the runout. You will have to put some washers on a few studs to hold the rotor in place. If it's bad enough to cause pulsation you can probably see it with naked eye. bg

 

[duspan]

yes the rotor slips off the studs,i made sure there was nothing stuck behind the rotor or on the hub?

thank-you

 

[B.G. Smith]

yes the rotor slips off the studs,i made sure there was nothing stuck behind the rotor or on the hub?



thank-you

Then it's back to what jelag said, the rotors need to be turned. Years ago they would always turn drums/rotors when sold new because they would warp while sitting on the shelf but I haven't seen that lately. bg

 

[betterthanstock]

After a long hard stop, immediately let off the brakes just as you come to a stop. By long hard, I mean anything on a downhill freeway ramp, or any downhill braking that brings you to an abrupt stop. Use the park brake if on a hill while at stop light if your brakes are hot. The hot discs can warp from the pressure of the pad. (I wonder if the parking brake could also warp the rear discs?)

Also some people say it is better going downhill to brake harder, intermittently, rather than a continuous soft application. May have something to do with glazing. If your truck sits unused for a week or more, the discs may rust where they contact the pads, so it may pulse until the rust gets polished, and if thick enough, will leave a thinner spot on the rotors, which causes pulsing.



Of course, avoiding an accident takes priority over warped brakes.

 

[duspan]

i just got done with having the rotors turn, and took it for a drive,but still have the problem,only on a easy stop you can feel it??? could the back brakes cause this problem also??? have not checked them yet,i've never had this problem with a brake job!!!!

thank-you

 

[B.G. Smith]

Yes, you have disc brakes on the rear too, even drums can cause pulsation. The antilock brake system will cause pulsation but mine makes a noise when it happens like on loose gravel or sand. You don't have different size trires on the rear than the front do you? bg

 

[duspan]

the brakes were working fine,till i changed the front pads... the tires are all the same size,and there is no noise...

thank-you

 

[DPKetchum]

Were they trued on or off the truck? That type rotor may need to be trued on the vehicle as the smallest out of clearance will show up with rack and pinion steering. The factory brakes on these trucks work great. You may need to just back factory.

 

[FullSack]

i had the same problem. Had the rear rotors either replaced or resurfaced (can't remember, that was over 100k ago) and it was as good as new - no more pulsing.

 

[duspan]

do the rear rotors come off like the front rotors???they look like the same slip on ones??

thanks