5.0 Mustang & Super Fords
American Powertrain HydraMax Master Cylinder Kit Install
Fox Hydraulic Clutch Conversion on a 1989 Ford Mustang LX Coupe - 5.0 Tech Inspection
The manual transmission is one of Mustang's most appealing components for those enthusiasts who enjoy running a stick-shift through the gears. We believe this is especially true for '79-to-present 'Stangs. We're sure many of you have rowed gears in a four-, five-, or six-speed 'Stang at some point, so you know the fun of kickin' and stickin' a V-8-powered Pony on the open road.
While heavy traffic probably reigns supreme as the most-annoying, disappointing variable in a stick-shift driving experience, the effort it takes to push in the clutch pedal can also bring the enjoyment level way down. A failure either in the transmission itself or some area of the clutch system can cause an even bigger headache, as problems in either area no-doubt will affect your wallet.
The clutch components that we typically discuss—discs, pressure plates, flywheels, and so on—for Foxes are not the focus this time. Nope, we're looking at a new take on the clutch-release bearing, better-known as the throw-out bearing.
Veteran Mustang owners know that clutch engagement and disengagement of the pre-'05 'Stangs is facilitated by six major components: the pedal, a quadrant, a cable, a throw-out bearing, a pivot ball, and a fork. In a nutshell, the clutch cable is the key player in this group. It's critically important because its failure—which usually stems from binding or being stretched, burned, or snapped—will put an end to any form of clutch operation. These maladies can leave your transmission incapable of being shifted into any forward or reverse gear.
If your Mustang is in need of a new cable or you just want a major upgrade, American Powertrain recently introduced a cool bolt-in master-cylinder/hydraulic-release-bearing setup that eliminates cable operation altogether. The HydraMax Master Cylinder Kit (PN 11705139; $629) for Foxes is operated by hydraulic fluid, similar to the clutch systems in the latest manual-trans Mustangs. We recently performed a HydraMax installation on a five-speed-equipped '89 5.0 LX.
Here is the traditional clutch cable and firewall adjuster. They must be removed to allow installation of the American Powertran HydraMax master-cylinder assembly. After disconnecting and removing these pieces, a template is used to locate and index the spot for two ¼-inch holes for the master-cylinder’s mounting bracket, which is bolted to the firewall with the included hardware.
The HydraMax master cylinder’s adjustable rod end is used to establish pedal height, and should be tuned to have roughly 1¼-inch of rod exposed for optimum height. The rod itself should travel down 11⁄16-inch when the pedal is pressed.
Because the surroundings in the driver-side footwell are tight, we’re using an out-of-Mustang pedal assembly to demonstrate exactly what happens on the other side of the firewall when installing the American Powertrain HydraMax hydraulic-clutch-conversion kit in a Fox ‘Stang. Once the bracket is attached to the firewall, the master-cylinder arm passes through the hole in the firewall and hooks onto the pedal pin. The master cylinder assembly then locks into the bracket and one bolt is installed in the side of the bracket to secure the master.
We placed the system’s small gravity-feed fluid reservoir at the back of the engine compartment on the driver side, just to the right (when looking at the car) of the power-brake booster. This reservoir must always sit above the master cylinder. The reservoir’s plastic snap-in port also serves as its mounting bracket, which is secured with two mounting screws that require small holes. With the container secured to the inner fender, the black rubber feed hose is attached.
This is the HydraMax slip-on, pre-bled hydraulic release bearing, through which DOT 3 brake fluid flows when the clutch pedal is depressed. This action creates pressure that pushes the bearing into the clutch fingers (to disengage the clutch). For all intents and purposes, the hydraulic piece’s actual function is no different than that of a Mustang’s standard cable-operated throwout bearing. However, the fluid makes clutch engagement/disengagement smoother, more efficient, and light-years more consistent. With this bearing, the clutch fork and pivot ball become unnecessary and can be removed from the Mustang. The kit includes a -3 braided line that secures to the bearing for feeding hydraulic fluid (red-capped port on the left) and bleeding the system when necessary. It’s important to make sure the bleeder line is placed outside the bellhousing and that the line is secure. The fluid-feed line is quickly added to prevent air from entering the bearing.
Setting up the bearing is a little tricky, as the procedure requires taking careful measurements for setting air gap between the bearing and clutch fingers to ensure the bearing will push the fingers the correct amount. Air gap should be between 0.150- and 0.200-inch, and American Powertrain provides several 0.060-inch steel shims that are installed behind the bearing to achieve proper gap. Unfortunately, this operation was done in one-man fashion and without the benefit of having a twin-post hoist or transmission jack. This complicated the process of capturing images of the measurement and actual bearing installation. A digital caliper and a straight edge are required for measuring from the face of the bellhousing to the top of the clutch fingers—a measurement we’ll designate as A, as well as from the face of the bearing to the face of the transmission, measurement B. To determine the amount of shims that are necessary for achieving the correct air gap, this formula is used:
A – (minus) B – (minus) 0.150 (air gap) 0.060 (shims)
It's important to subtract 0.100-inch from the total after the double subtraction. This is the thickness of the straight edge.