Thursday, August 30, 2012

How to Remove the Rustiest of Brake Rotors

After sitting for two years the brake rotors on project Miata were solidly fused to the hubs. They were also badly warped and needed to be changed. Armed with a twenty pound sledge, propane-oxygen torch, three jaw puller and a lot of profanity, I was able to break them free. Here's how I did it.

Heat has great effect on rusty parts and I use a propane bottle on rusty bolts all the time but its not up to the task of brake rotors. The rotor acts like a heat sink because that's how its designed to transfer the forward motion of the vehicle into heat in the air. I acquired a propane-oxygen torch from Lowes for less than $40 to get an adequate amount of hot.

The instructions are straight forward and offer three settings of flame for cutting, welding, or brazing. The first step is to light the torch on propane only by opening the propane dial 1/16 turn. I cracked the valve a tiny amount and heard a faint hissing sound of gas. Good, now I'm ready to light. I put the included igniter at the end of the torch and began throwing flint sparks. For several moments no flame emerged. Baffled, I shifted the igniter to be next to (not in front of) the torch and POOF went a fire ball in my face. Once I verified my eye brows were still in place, I tried again. Word of warning, the propane valve is very sensitive. It need only be open the tiniest fraction of a turn to ignite the torch.

With the torch finally lit, I dialed in some oxygen and put it on the middle heat setting which may also be effective for welding. I applied the torch all over the hat section of the rotor from the front, and to the back side of the hub as much as possible. Once the rotor was radiating heat, I put the torch out and started swinging the hammer on the back side of the rotor. Remember to wear ear plugs when banging metal parts with a big hammer. After about ten minutes of banging, the front rotor succumbed and released its grip on the hub. The other front rotor went about the same so I moved onto the rears.

Note crack visible at radius connecting hat and disc
I heated up the rears and began swinging the hammer against the back side of the disc. To my amazement the rotors cracked instead of coming off. With the disc completely separated from the hat, banging on the disc was futile. In frustration I cut the disc free with an angle grinder and mounted a three jaw puller on the rotor hat.

I thought this would easily dislodge the remnants of the rotor. The puller did the job but only after exerting an incredible amount of force. I could actually see the hat bending at the edges before it came off. Word of warning part two; make sure to put a few lug nuts on the wheel studs to catch the rotor. Without them, parts go flying everywhere.

So with all the rotors removed, I slathered the hubs and wheel studs in anti-seize. I know the stuff is disgusting, but I don't want anyone to have to face this nightmare again. Now that the rotors were done I moved on to replacing the two frozen calipers and all the pads. Once I had everything bled I ventured out to the nearest parking lot for a slow speed test drive. Everything seemed fine after the first few applies, so I tried stomping on the brake pedal. Initially, the car decelerated great. Then, the pedal flopped to the floor and slowly came to a halt. The rusty rear brake line burst. Back to the garage to splice in a new line and re-bleed the rear cylinder.

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