 These Fiat and Lancia vehicles are equipped with a load sensitive brake pressure compensating valve. This device is attached to the underbody of the car in the vicinity of the rear axle, and is controlled by a rod which is connected to the rear axle. The function of the compensator is to regulate the amount of hydraulic pressure to the rear brakes in order to prevent rear brake lock-up. The amount of pressure is directly proportional to the load on the rear wheels. As the load increases or decreases, the rod transmits these changes to the compensator, decreasing pressure under light load and increasing pressure under heavy load. This compensates not only for the weight of passengers or items which may be in the trunk, but also for the weight transfer that takes place during braking.
So how does this affect brake bleeding? If you have the vehicle supported by the frame on a lift or on jackstands with the rear axle hanging at full extension, then the compensating valve is cutting off the flow of brake fluid to the rear brakes, making them impossible to bleed. So, on Lancia Beta, Fiat Brava and Fiat 124 Spider and Coupe, when bleeding rear brakes, be certain to have the rear axle supported in such a way that it is at normal ride height, relative to the body.Happy bleeding! |
