![]() ![]() Either there is air in the hydraulic system that will require bleeding the system, or there is a brake fluid leak (leaking caliper, split brake line), or the master cylinder assembly is bad (leaking internal seals, etc). Solution: If the brake pedal is soft and spongy or goes all the way to the floor, the problem has nothing to do with the electro-hydraulic system (pump motor, pump, PWS, motor relay, wiring). Problem: The brake pedal is spongy or the brake pedal goes all the way to the floor, and stopping power is poor. The figure below shows the various parts of the master cylinder.īelow is a circuit diagram for the pump motor, relay, and the part of the PWS that controls the pump motor. To avoid throwing parts at the system in hope of fixing it, a relatively simple diagnosis will determine what part has failed. This relay (which Ford refers to as an “anti skid relay” even though it isn’t directly related to the ABS system) is the most common part to fail and cause a loss of power braking and the BRAKE and ABS lights to turn on, but there are other possibilities as well. Running this much current through the PWS directly would kill the switch almost instantly, so a relay is used to indirectly power the pump motor. The pump motor draws around 20 Amps in normal operation. The system is designed so the pump runs quite often for brief periods of time the keep the pressure as constant as possible. A pressure switch (called a Pressure Warning Switch, or PWS in some Ford manuals) measures the pressure in the accumulator and turns on the pump if pressure gets too low, and turns off the pump when pressure reaches the desired level. An electric pump is used to pressurize the brake fluid. The power brake system uses brake fluid stored in a hydraulic accumulator (basically a pressurized reservoir) at pressures around 2500 psi to provide pressurized brake fluid for power braking. These, and a few other related problems will be discussed below. Another not as common problem is the BRAKE and ABS lights illuminating briefly under hard or repeated braking. One relatively common problem with the braking system is a loss of power braking (often referred to as a “hard pedal”), accompanied by the red BRAKE and yellow ABS dash lights illuminating. The ABS part of the system is much more difficult to troubleshoot, and will not be discussed here. This article will discuss troubleshooting the power brake part of the braking system only. This means that a loss of power braking has nothing to do with the ABS computer, wheel speed sensors, etc. If the ABS part of the system is disabled, power braking will not be affected in any way. If there is a failure of the ABS part of the system due to a failed wheel speed sensor, open or shorted solenoid valve, etc, the ABS computer will disable the antilock part of the system, and turn on the yellow ABS light on the dash. None the less, the power braking part of the system and the ABS part of the system are nearly 100% independent of each other. Unlike modern ABS systems that use a standard vacuum brake booster and a separate hydraulic control unit (HCU) to provide the ABS, the Teves II system incorporates both the power brakes and ABS integrated into the master cylinder. The 1987-88 Turbo Coupe, as well as the early Thunderbird Super Coupes and some Lincolns from the era, use a Teves II electro-hydraulic system to proving both power braking and antilock braking. Close the bleeder and repeat at each wheel, making sure to top off the master cylinder each time.Troubleshooting the teves II electro-hydraulic braking system used on the 87-88 turbo coupes If you check the hose it should be full of fluid with no bubbles. Top off the master cylinder, then pump the brake pedal a few times. Now, just put the other end of the tube over bleeder, and open it. Pour just enough fluid into the jar to cover the end of the hose - this way no air can be sucked back into the system. To make your own, drill a hole in the lid of the jar that's just big enough to squeeze the hose through without it falling out. You can buy a set-up like the one pictured above, with the added bonus of a magnet to keep the fluid higher than the caliper, for $5 at most auto parts stores. ![]() You will also need a length of hose that fits over the brake bleeder nipple. You can make one yourself from any clean jar or bottle with a lid you happen to have around. This technique is nearly as simple as using gravity, but is also much faster, is the bleed bottle. ![]()
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