'94 405 Rear Calipers

jay · Post by **jay** » 16 Oct 2001, 17:33

I am currently replacing the major components of the rear disc braking system on my 405 (calipers, rotors, and pads). This is my first time replacing calipers, so I would appreciate some guidelines on properly bleeding the system when installing the new calipers (without using special brake bleeding tools).
Thanks

Dave Burns · Post by **Dave Burns** » 17 Oct 2001, 05:05

If you car has antilock brakes there may be special requirements for bleeding though I'm not sure, after fitting the calipers make sure the pistons are pushed as far in as possible, smear copper grease on the bleed nipple threads, find a piece of clear flexible tube that is a snug airtigh fit over the nipple, get a jar with about an inch of fluid in it and imerce the other end of the tube in to it, open the bleed nipple two turns and have an assistant press the brake pedal with force, returning the pedal slowly to the top and then repeating until the fluid flows free of air bubbles, at which time the pedal should be held at the bottom of the stroke while the bleed nipple is tightened, keep an eye on the fluid level in the reservoir, if it is allowed to get too low the entire system will require bleeding, it is important to press the pedal with force as this creates turbulence inside the calpier and releases trapped bubbles. I suspect you are doing this work on a high mileage car, if so it is wise to replace the master cylinder or at least re-new the seals, if you are not going to do either you must use the same brake fluid that is in the system at present, believe it or not a change of fluid from a different manufacturer may attack and partially disolve the rubber seals leading to total brake failure, this happened to me and through shear good fortune at low speed on a quiet road, fluid that was crystal clear six months earlier was found to be jet black from dissolved rubber.
Dave