In this article, we’re going to discuss some simple tech info where we will show you the steps you need to take to adjust your brake booster pushrod. So recently, we installed a '93 Cobra-style brake booster onto our 1993 silver hatchback Fox Body Mustang, which has our SVE SN95 Cobra-style 5-lug brake conversion. We're not going to get into the detail of that particular kit, but if you are interested, check out our article where we explain the kit and show you how to install one onto a Fox Mustang.
Upgrading the brake booster has led us to this article. Anytime you install a new master cylinder or a new brake booster, it is required that you verify and adjust the brake booster pushrod length if it’s needed. Not doing this will result in either dragging brakes or a low pedal which can be very dangerous! In this article, we’ll explain the very simple steps you need to take to ensure the brake booster pushrod is properly adjusted. Now, you can purchase a specific tool for this or use what you have lying around the shop.
Specialty Tools Needed
- Digital or dial caliper
- Small straight edge
- Set of midget wrenches
Now, we know a Vernier caliper can seem simple, but you will need to understand how one of these calipers works to obtain some of the measurements.
- To ensure we are clear and concise, we will be showing these steps on the workbench. To begin, we first need to measure the pushrod bore depth of the master cylinder and write this down. This measurement will be from the bottom of the radius in the pushrod bore to the back face of the mounting flange on the master cylinder. Insert a tool that will fit inside the bore and is small enough to reach the lowest point in the bore.
- Next, use a small straight edge and position it across the mounting flange of the master cylinder. Using a marker, place a mark where the straight edge intersects with the depth checking tool.
- Remove the depth checking tool and measure the distance using a digital or dial caliper. You’ll use the lower jaw section on the caliper for this.
- Write down this number and call it something you can reference. For example, I’m calling this "M1" for measurement one.
- Now we can go ahead and measure the distance from the back of the master cylinder to the back face of the mounting flange. Use the depth rod section of the caliper to obtain this measurement.
- Write down this number. I’m calling this "M2" for measurement two.
- Subtract "M2" from "M1" and write this down as "M3".
- In order to prevent accidental pre-load of the master cylinder, subtract another 5 to 10 thousandths from "M3". This will be the final number.
- Go ahead and measure the distance that the pushrod protrudes from the master cylinder mating surface on the brake booster to the tip of the pushrod. Use the upper jaw section on the caliper to measure this distance. Depending on the components and how the pushrod is set from the factory will dictate whether or not you have lengthened or shortened the pushrod.
- Whatever is required, hold the flats on the shaft with a suitable small wrench. Loosen the jam nut using the correct size wrench and then turn the pushrod adjusting screw in or out to the desired length.
- Check the length again. Whenever this is good, mark the tip for reference just in case you accidentally rotate it a little; you know where the orientation was.
- Run the jam nut down against the shaft and then snug it down. This doesn’t have to be crazy tight.
- Once that is complete, you can continue with what you’re doing and you’re good to go.
Alright, folks! That’s it. This process is a lot easier than what people make it out to be. The hardest part is removing and installing the components into the vehicle. Which by the way, if you own a Fox Mustang and would like to see the process of installing a '93 Cobra-style booster, check out our article.
Until next time, for all things 1979 to present Mustang and SVT Lightning; keep it right here with the Real Mustang eEnthusiasts, LMR.com!