Before you disengage and bring in the brake calipers to service the 1990 Deville and Fleetwood models be sure to depressurize the hydraulic accumulator because the hydraulic system has brake fluid under very high pressure if the car is equipped with anti-lock brake system. Open the master cylinder bleed screw cap and take out two-thirds of brake fluid using a syringe and then lift and securely jack up the automobile. Get out the wheel and tire assembly, reinstall only two bolts to hold the disc brake rotor in place, and then use pliers to install the piston in the caliper to the bottom most position. If caliper has been removed it is now necessary to release the brake hose, to discard gaskets and to plug the holes to avoid losing the liquid. Next, you must remove the caliper mounting bolts and sleeves after that, the caliper will have to be taken off. For installation, check the bolts and bushing for damage, and applying grease on the bushings you should then place the caliper over the rotor. Secure the mounting bolts of the caliper to the respective torque, verify the clearance of the caliper on the bracket stop and fit the brake hose with new gaskets. Following bleeding of the brake system, ensure that you replace the wheel and tire assembly, lower the car and check the amount of the brake fluid. The process for the 1991-93 models is somewhat The same with the use of a C-clamp in order to force the piston into the caliper. During rebuilding of dual piston calipers, the caliper has to be detached after which the piston has to be blown out using compressed air and the interior assessed for signs of wear and the entire hardware has to be cleaned before being rebuilt. Replace the seals used in the caliper and also the pistons and boots that may be worn out, then the caliper has to be reinstalled and the brake system adequately flushed.