Minivan brake concerns; loud-locking SUV door

Q : I have a 2006 Dodge Caravan. I have replaced the front brake rotors and pads.

I also replaced the rear drums, brakes, wheel cylinders and park brake lines.

So every corner is brand new, yet when the brakes are applied, the pedal shudders slightly and a growling is heard.

On hard braking this is so strong the rear wing windows just pop open and vibrate violently and rattle noisily.

What on earth could be the problem?

A: The brake vibration could be caused by many problems but I would start by checking for a rear brake drum that is not installed fully or is warped. Dirt and rust are the cause of many brake vibration problems.

Before any drum or rotor is installed, the mounting surface on the hub or axle and the inside surface of the rotor or drum must be clean.

Otherwise, the drum or rotor will wobble as it turns and cause the brake shoes or pads to vibrate when the brakes are applied.

If everything is clean, have the inside of the brake drums measured for out of round. If brake drums have been improperly stored on edge, they can warp just from the weight of the drum. The drum may need to be turned or even replaced.

You state that the drums are new, but if the drums have been machined on a brake lathe and not finished properly, a fine thread is left on the drum surface. This thread will grab the brake shoes and cause them to rapidly move in and out.

The rear brake shoes are pulled away from their normal mounting position by the drum and then the springs snap them back into place.

This problem would also explain the growling noise, because if this occurs rapidly, it can sound like a groan or growl.

Finally, check the torque on all the wheel nuts. Uneven torque will warp a drum or rotor. If they are re-torqued properly within a couple hundred kilometres, the problem may disappear.

Otherwise, the drums or rotors may need to be turned to eliminate the warp.

Q : I have a Ford Expedition. One door lock makes a very loud vibration noise on locking.

How can I fix it?

A: The power door lock mechanism is actually a reversible electric motor with a small pinion gear on it attached to a linear rack gear.

When you press the lock or unlock buttons, power is momentarily supplied to the motor and as it turns, it rapidly moves the linear gear one way, which in turn moves the mechanical lock linkage.

The lock is moving so the motor is operating but a sticking or binding linkage or lock mechanism is likely causing the vibration.

The motor tries to move the mechanism but it only moves part way and then bounces back. As you hold the lock button, the motor rapidly keeps trying to move the lock mechanism and you hear this as a buzz or vibration.

Usually, this type of problem can be solved by removing the inner door panel and checking the lock linkage for binding.

There may be some sound deadener that has moved out of place or the lock mechanism needs some lubrication.

Be sure to operate the locks to make sure everything is working properly before replacing the door panel.

Jim Kerr is a master mechanic and recently retired teach of automotive technology. Send your questions to Jim at jkerr@herald.ca