Original by eldobro

I went through this with a 91 Seville, which has the same set-up in the rear. I replaced all the bushings, caliper bolts and clips, but the rattle was still there. I wound up smacking the caliper with a rubber mallet and poking here and there with a screwdriver until I found the problem.

The rattle didn't start until I replaced the original pads. I dug the old pads out of the shop garbage and measured them. I found that they were slightly narrower side to side. That and the wearing of the caliper bracket where they hang caused the rattle. There was room now for them to move around with the caliper when I would hit bumps with the car.

I tried an experiment Using the new pads as a gauge, I had a new surface welded up on the caliper bracket and then cut down so the pads still had clearance side to side, but not enough for the caliper to build up momentum when I hit a bump. I put it all together, drove down a rough road and the rattle was completely gone. after all this time, the rattle has never returned.

originated by allantesource

It is also a good idea to periodically check the run time of your ABS pump to repressurize a completely depressurized ABS system. You can check the condition of your ac***ulator at the same time.

First, with the ignition off, depressurize your system by pumping the pedal all the way to the floor 25 times (full and deliberate pedal applications, not quick jabs). At some point, you should experience a change in the feel of the brake pedal. Make a note of this.

Then, without touching the brake pedal, turn the ignition on, and time how long your ABS pump runs before shutting off. It should be 30 seconds or less. If it runs longer than that, most likely it is failing, and should be replaced promptly. The pump relay should be replaced at the same time.

After the pump has shut off, you can check the condition of your ac***ulator. Turn off the ignition. Then start depressing the brake pedal again, but this time count the number of pedal applications before the pedal comes up off the floor and the feel of the pedal changes (it will become rock hard). This should be about 15 applications. If it is less, then your ac***ulator is weak and should be replaced. If you continue to run with a weak ac***ulator, it will cause your pump to work too hard, and possibly it could fail prematurely.

by allantesource

(depressurize system)

First the ABS pump gets bled, key on, until bubbles are gone.

A clear hose gets attached to the pump bleeder screw, the end of this hose submerged in a jar with about an inch of clean brake fluid in the bottom.

Open the bleeder screw on the pump, and let it run until it clears up. About 30 seconds at a time is all you should let the pump run. (turn OFF key, shut off bleeder screw) Let it rest for a minute, then another (open bleeder screw then turn pump ON) 30 seconds, etc. Generally three cycles of this will be enough. Keep the reservoir full, within 1/4 inch of the full line.

Next you bleed through the bleeder screw on the master cylinder. Again, have a clear hose on the bleeder, end submerged into a glass jar with clear brake fluid.

Open the bleeder screw. Turn the key on, and let it run until fluid is clear of bubbles. 30 seconds on cycle, then rest.

(AT THE WHEELS)

I will walk you through manual bleeding, which I what I do. It requires two people.

This portion is performed with the key off. The order of wheels is RR, LF, LR, RF. Attach clear hose to bleeder, end submerged in glass jar with 1" of brake fluid in it.
Have an assistant pump pedal a few times, then hold, and open bleeder screw until flow stops. Tighten screw before pedal is released. Repeat as needed until fluid is clear and there are no more bubbles. Keep an eye on the fluid level in the reservoir.
This whole portion of the bleeding is with KEY OFF.

by allantesource

As Zal found out, it is IMPERATIVE to depressurize the system first before bleeding the system. Also, the easiest way to get fluid out of the reservoir is to drain it into a small funnel and collection container placed below the front corner of the reservoir. The fluid change procedure is reprinted below, in two sections.

Simplified brake fluid change procedure

Regular brake fluid changes for all 1987 through 1992 Allante's with the Bosch III ABS system will significantly improve the life of these systems. By not changing fluid, over time old brake fluid loses its anti-corrosion properties. It appears to start attacking the metal in the system, especially the aluminum housing. Then crud starts to form. This crud works it's way into the sealing area, and starts abrading the seals. As internal seal leakage increases, plausibility fault codes start appearing, turning on the red brake warning light. Once the damage has occurred, the ABS system must be replaced to correct the error conditions.

For a couple years I have been following a simplified brake fluid change procedure. We have also changed the brake fluid in a number of local club members' cars following the same procedure. I thought I would pass it along, to get more people to change their brake fluid. Doing this annually is a very good idea.

Start by depressurizing the brake system by pumping the brake pedal 25 times with the key off. It is not a bad idea to unplug the ABS pump after doing this. Put a piece of cardboard under your car, under the master cylinder area to soak up a small amount of fluid which invariably will drip down. Next, remove the air duct between the airbox and the throttle body. With a jar or can and small funnel underneath, pull the hose off the lower front corner of the brake fluid reservoir. Allow the fluid to drain completely. If the fluid is really black, the reservoir really should be cleaned.

The reservoir can be removed from the master cylinder as follows. Disconnect the hose(s). Insert your fingers under the front, and pull up. There are three "feet" or ports on the bottom of the reservoir, which will pop out of grommets in the top of the master cylinder housing. Immediately clean off the area under the reservoir, to make certain no foreign material gets into the openings.

Next, remove the screen from the reservoir. Any of a variety of solvents can be used to clean the inside. It may take a couple hours if your reservoir is really loaded. Brake pad cleaner, lacquer thinner, TSP, and degreasers will all work to some degree. I purchased a used ultrasonic cleaner specifically for this purpose, which works well. After cleaning the reservoir, it must be THOROUGHLY flushed with clean brake fluid to remove any trace of cleaning solvents and moisture.

Then reinstall on the master cylinder, and reconnect hoses. Refill with clean brake fluid, preferably DOT 3. NEVER use DOT 5, synthetic silicone brake fluid. Some brake fluids are DOT 3 and DOT 4 spec. Those are OK too. Next, take a clear piece of hose, about 2' long, 3/16" ID, and attach it to the bleeder on the ABS pump. Submerge the end in a collection jar.

Plug the ABS pump back in, and turn on the ignition for about 30 seconds. Watch the hose for bubbles, and the clearing of the dark color from the fluid. Repeat several times as necessary until bubbles are gone and fluid is clear. A few very small bubbles are OK. Do NOT open bleeder screw too far. When you are satisfied, with pump off, close the bleeder, and refill reservoir.

Next, attach the clear hose to the bleeder fitting on the side of the master cylinder, pointing toward the right side of the car. Open the bleeder between 1/2 turn and a full turn. Submerge the end of the hose in the collection container. Turn on the ignition, and run for 30 seconds.

Then shut off and wait a minute or two and repeat as necessary until fluid is clear and no bubbles are present.

Then shut bleeder, remove hose and collection container. Refill the reservoir. That's the end, other than reinstalling air duct and cleaning up. What you have done is to replace all the fluid in the working portion of your ABS system.

IT IS IMPERATIVE THAT WHEN BRAKE PADS ARE REPLACED AND CALIPER PISTONS NEED TO BE COLLAPSED THAT BLEEDER SCREWS MUST BE OPENED AND OLD BRAKE FLUID MUST BE DISCARDED. IT MUST NEVER BE FORCED BACK INTO THE ABS SYSTEM. THIS IS THE CASE WHENEVER YOU ARE REPLACING YOUR BRAKE PADS, WHETHER OR NOT YOU HAVE FOLLOWED THE ABOVE PROCEDURE TO CHANGE YOUR BRAKE FLUID.