Master Cylinder Service

Master Cylinder Service Points : Master Cylinder Service, Master Cylinder Removed, Master Cylinder Rebuild (Repair), Bench Bleeding a Master Cylinder, Installing a Master Cylinder, A faulty master cylinder usually leaks out the rear piston or leaks internally. When leaking out the back, you should be able to detect brake fluid in the rear boot or-on the firewall. When the leak is internal the brake pedal will slowly move to the floor. Inoperative valves in the master cylinder also required repairing and servicing. Master Cylinder Removed To remove a master cylinder, disconnect the brake lines from the master cylinder by using wrenches. Then unbolt the master cylinder from the brake booster or firewall. Sometimes, the pushrods must be disconnected from the brake pedal assembly. Master Cylinder Rebuild (Repair) Many times a bad master cylinder is replaced with a new one. A replacement may be cheaper than the cost of labour and parts for repair. Moreover a new one is more reliable than a repaired one. To repair a master cylinder, drain the fluid from the reservoir. Then completely disassemble the unit following the instructions contained in a service manual. Basically, you must hone the cylinder and replace the piston caps and valves, clean the parts in brake fluid or with recommended cleaning fluid.

After cleaning, measure the piston to cylinder clearance, use a telescoping gauge and an out side micrometer or a strip type feeler gauge. The cylinder must not be tapered or worn beyond, not corroded, pitted or scored. Replace the master cylinder if the cylinder is not in perfect condition after honing.

Blow all parts dry with compressed air. Blow out parts and check that they are not obstructed lubricates the parts with brake fluid and assembles the unit using manufacture’s instructions. Fig.6.56 shows an exploded view of a typical dual (Tandem) master cylinder.

Bench Bleeding a Master Cylinder To install a master cylinder, replace the reservoir cover after bench bleeding. Bolt the master cylinder to the firewall or booster. Check the adjustment of the push rod if a means of adjustment is provided. Without cross threading the fittings, screw the brakes lines in to the master cylinder. Lightly sung the fittings. Then bleed (remove air from) the system.

Tighten the brake line fittings. Fill the reservoir with fluid and check brake pedal feel. Test-drive the car.