Copious amounts of brake dust accompanied with scraping noise


#1

1978 chevy G30 conversion van with a 5.7 liter 350 engine named, lucky number two. The noise started a month ago and has only gotten worse or at least takes less time to occur. It’s a sort of scraping or grinding sound that pulsates and the pulses get shorter as the speed increases but breaking changes nothing except time intervals between pulses. My first thought was breaks or bearings so I changed the breaks repacked the bearings cleaned, greased and visually inspected break parts, bearings, races, ect and find no signs of damage. Caliper pushes in with out too much clamp twist force. But still the noise and now copious amounts of break dust on both rims but one more than the other. It never makes the noise after the van has sat awhile until I drive a couple of miles. Today I drove around only using the back breaks and nearly crapped my pants but it the noise never occurred with leads me to believe it’s the caliper. But why all the break dust on both rims and why doesn’t applying break change the noise? Also Should add but don’t think it’s relevant but the power steering is hissing especially when the wheel is fully turned. I don’t think I have a hydro boost because there are no lines connecting the pump and break system that i can see. please help me diagnose.


#2

Did you turn the rotors? Rough surfaces can tear up the new pads and prevent them from bedding in. Did you check the brake (not break) shields on the inside of the front rotors? It is very easy to bend these stamped metal shields so they scrape the rotors. Does the noise happen if you jack up a corner and just spin the wheel? Isolate it by spinning one then the other. If its a brake shield bend it a small bit away from the surface. Let us know what you find.


#3

when I spin the rotors there is resistance and some noise on both Which goes away when I remove caliper assembly.Why would a metal shield scraping cause my rim to turn black? I have not had the rotors resurfaced because I’m trying to diagnose before spending money. Also the breaking does not pulsate only the noise.


#4

“Caliper pushes in with out too much clamp twist force.”

There should be almost NO clamp twist force required. Treat your baby to new front calipers (and different, i.e., more expensive, pads to stop the dusting).


#5

changed The caliper and still with the noise. Took the rotors In to have them resurfaced And they say they are too thin. Planning to change them soon but had a couple questions. First, is there any harm in putting old bearings on the new races that come pressed in the rotor? Second could my scraping noise even be caused by the rotor given these two factors; it will only make the noise if I have used the brakes a few times and there is no brake pulsing?


#6

If the new rotors don’t eliminate the problem replace the brake hoses that lead to the calipers.
With age the inner wall can colapse and a small piece act as a check valve. Allowing fluid to flow to the piston when the peddle is depressed, but when you release the peddle a little of that pressure remains and keeps the piston from retracting,

Yosemite


#7

It’s all 36 years old…It’s safe to assume it’s all junk. And NO, bearings and races are sold as matched sets…If the rotor / hub comes with races, discard them and install a set purchased as a pair… So you will need two rotor/ hubs, inner and outer bearings and seals and a pair of calipers and a set of new brake pads and possibly a hardware kit…