Brake pulsation mild to extreme each trip

[Rory]

My old mechanic would always put new rotors on his jobs. He said turned rotors even when in spec tended to warp.

This makes the most sense so far. But should I feel rotor pulsation in the steering wheel ? I feel nothing in the steering wheel.

 

[Rory]

I just ordered new rotors and grease seals, new master cylinder, new front and rear flex hoses and clips. The drums were new less than 120 miles ago. If this does not fix the problem I will be real stumped.

 

[Rory]

Are the bearings new and if they are did they replace the races in the rotors. Do know how many times the rotors have been cut? If there been cut to many times they are out spec and thin, that's when the problems start.

The rotors were only machines once by a Brake only service shop. Not that that means they knew what they were doing. As I recall they were training a couple new employees.

 

[Clone TIE Pilot]

Cheap rotors can warp pretty easily. This happened to my Mom's old Taurus years ago with new Autozone brand rotors.

 

[Rory]

The brake pulsation that gradually appeared only after driving so many miles was because of faulty rotor machining by a brake service shop. What they did wrong was to machine one plate of each rotor down to less than the half thickness of the other plate. As brake heat would expand the thicker plate more than the thinner plate the rotors would warp out of shape more and more the hotter they got. Rotors must be machined evenly on each side so as to not expand unevelnly as they heat up.
The car now has all new flex hoses, new rotors, new drums, new master cylinder and a large amount of old brown fluid flushed out of the system. The system was flushed 17 years ago but in that time the fluid turned nasty brown.

 

[69hurstolds]

So now you're reporting that all is well in the braking department? Glad you found that out, though. If you hadn't, it would have driven you mad.

 

[ssn696]

The brake pulsation that gradually appeared only after driving so many miles was because of faulty rotor machining by a brake service shop. What they did wrong was to machine one plate of each rotor down to less than the half thickness of the other plate. As brake heat would expand the thicker plate more than the thinner plate the rotors would warp out of shape more and more the hotter they got. Rotors must be machined evenly on each side so as to not expand unevelnly as they heat up.
The car now has all new flex hoses, new rotors, new drums, new master cylinder and a large amount of old brown fluid flushed out of the system. The system was flushed 17 years ago but in that time the fluid turned nasty brown.

Thanks for reporting out on the diagnosis and solution. I like closure...

 

[78Delta88]

The brake pulsation that gradually appeared only after driving so many miles was because of faulty rotor machining by a brake service shop. What they did wrong was to machine one plate of each rotor down to less than the half thickness of the other plate....

Yep, that's someone that doesn't know how to use a brake lathe. Sounds like they didn't mic the final product either, as it would have been out of spec.

 

[1320chevy]

My 1979 Regal has had the Rotors machines previously and just got brand new drums installed. Every time I drive the car it starts out with smooth brake action. Gradually a brake pulsation comes on. The farther I drive the worse the pulsation gets until it is unbearable at about 4 to 5 miles of town driving. The same happens the next time I drive the car. I feel no pulsating in the brake pedal or steering wheel. Rear wheel cylinders were rebuilt 7K ago. With the car up on a hoist there is no brake dragging. So what is causing the oncoming pulsation on each trip? It can get so bad that people stare at me lurching behind the wheel as the car pulsates to a stop and wonder if I am an epileptic and having a seizure.

What you need to do is to check the runout of the rotors, both cold and hot. Excessive runout can be from being permanently or temporarily warped by heat. Every time a rotor is cut it loses some integrity and becomes more prone to warping. You can also check the assemblies for binding by using a temp sensor "gun" and seeing that all wheels are similar temp after running. One hotter wheel if the one you need to examine.
don't forget your tires an out of round tire with one or more broken internal belts can do that as well.

 

[1320chevy]

What you need to do is to check the runout of the rotors, both cold and hot. Excessive runout can be from being permanently or temporarily warped by heat. Every time a rotor is cut it loses some integrity and becomes more prone to warping. You can also check the assemblies for binding by using a temp sensor "gun" and seeing that all wheels are similar temp after running. One hotter wheel if the one you need to examine.
don't forget your tires an out of round tire with one or more broken internal belts can do that as well.

Just saw your solution. Good. They don't mention this but brake fluid is hygroscopic (pulls water into it right out of the air) As such, it should be replaced every couple of years. I usually just drain the master cylinder reservoir with a turkey baster and refill once a year. No bleeding or anything else necessary.