2nd Gen Non-Engine/Transmission 2nd Gen Pulsating brake problem

[Partyat33]

Recently had the steering gear replaced. Now brakes pulse very badly. Thought it was just me so I replaced from pads and rotors. No change. Took out anti-lock fuse. No change. I an not that familiar with the connection between the PS and the brakes. Any help would be appreciated.



Dennis

 

[JLandry]

Dennis,



When you say the brakes are pulsing, do you mean the vehicle braking action isn't smooth? Or do you mean you can feel the brake pedal pulsing (or both)?



Did you replace ALL the rotors and pads or just the front?



Did you check the rotor runout and thickness variation on either the old or new rotors per the factory service manual?



Regards,



John L.

 

[Partyat33]

The braking action isn't smooth. No pulling in the steering at all. I did not check the rotor thickness. I did not do the rears it 'feels' like it is in the front but I can tbe sure.

Dennis

 

[B.G. Smith]

Only connection between the brakes and the steering gear is the power steering fluid. Was the pump relaced also? Sounds like a pressure control valve acting up somewhere in the system. bg

 

[JLandry]

Dennis,



You're going to want to check both the thickness variation and lateral runout (side to side movement) for all the brake rotors to find out which one(s) have a problem. I can almost assure you have one or more "wobbling" rotors with excessive lateral runout... either the old or new. The cause could be the rotor itself, something between the rotor or the hub (dirt or rust), or a warped hub.



To check the thickness variation, you'll need a 1-2" micrometer like THIS or THIS or THIS. With the lug nuts installed and torqued to spec, you'll need to take measurements approx. 1" in from the outer edge in 6 to 12 places around the rotor. The maximum allowable variation is only 0. 001" between all of the measurements.



If any of the rotors fail the thickness variation check, there's no choice but to have them turned on a brake lathe or replaced.



To check the lateral runout, you'll need to use a dial indicator kit similar to THIS or THIS. With the lug nuts still installed and torqued to spec, clamp the dial indicator support somewhere on a solid non-moving area near the rotor, usually the brake backing plate or brake mounting area (not the caliper), and set the dial indicator approx. 1" in from the outer edge of the rotor. The maximum allowable lateral runout is 0. 005".



If any of rotors exceed the maximum allowable lateral runout, but still meets the thickness variation check, then you can try to reduce the lateral runout by doing the following:



1. Removing the offending rotor.

2. Cleaning both the backside of the rotor and the hub face it mounts on with a wire brush and/or an abrasive pad such as ScotchBrite.

3. Remount the rotor, install and torque the lug nuts to spec, and recheck the lateral runout.



If the offending rotor still exceeds the lateral runout tolerance (0. 005" maximum), then:



1. Mark the position of the rotor in relation to its hub with a marker, grease pencil, or paint.

2. Remove the rotor, turn it by one mounting stud position to the right or left on the hub, and reinstall with the lug nuts retorqued to spec.

3. Check the lateral runout again.



If the offending rotor still exceeds the lateral runout tolerance (0. 005" maximum), then repeat the above procedure by turning the rotor one more position on the studs (same direction) and remeasure. If you find a position where the lateral runout is within spec, mark the rotor and hub for future reference and you're done. If you ever need to remove the rotor in the future, you'l want to reinstall it in the exact same position.



Now having said all that, a MUCH easier way of dealing with this and avoiding all of the above is to have the brake rotors machined (cut) while still mounting on the vehicle by a Pro-Cut brake lathe. You can find your nearest equipped shop HERE. I recently had to have the rear rotors turned on my truck because of a warped hub. The result was (is) perfectly smooth braking.



Best regards,



John L.