Hitman's Pontiac Trans Am Page | 1978 Pontiac Trans Am
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Master Cylinder

Doing the Master cylinder was actually quite easy. It is the steps after doing this that becomes the hard part, but I have more on that on a separate page. Anyway, to remove the master cylinder all you have to do is empty out any brake fluid in the front and back reservoirs of the unit. I used a turkey baster to do this. You want to make sure that AT NO TIME, and I stress AT NO TIME get any brake fluid on your paint job! Brake fluid works well for a paint remover so be careful. Next, remove the front and rear brake lines from the unit making sure that you don't bend or twist the lines. I used a 9/16 open ended for this. Next, remove the 2 mounting bolts that holds the unit on the power brake booster. Now when you remove these 2 bolts, you will also notice that there is a bracket attached here that also holds the combination valve in place (once again, more on this valve on another page). Remove this and the unit slides right off. Now, I am not going to get into how to rebuild a master cylinder because they are so cheap to replace, why spend the time to rebuild one? If you really want to know how to do it, send me an E-mail me and I will tell you how. So now you have your new master
cylinder and are ready to put it on the car right?.... wrong.... You must first bench bleed the new unit in order to remove any and all air from the unit. Typically, new units come with a simple kit to do this. There are 2 red plastic valves that screw into the front and rear brake line holes. Then attach the plastic tubes to them and run them up to empty into the front and rear reservoirs respectively. The kit also comes with a handy clip to hold these tubes into place. Make sure you fill the reservoirs with enough brake fluid to do the job. You need to run the ends of the tubes below the level of the fluid so that you don't suck air back in when you release. Clamp the new unit by the mounting bracket and NOT by the body of the unit. Clamp it in place and use a large Phillips screwdriver to slowly push the plunger in to circulate the fluid throught the master cylinder. This takes quite a few times to do this and you want to make sure all of the air is out of the unit. I did it about 20 times or so.

Once you have successfully removed all of the air from the unit, place the caps back on the plastic fittings and mount the unit back in the car making sure that you also put the combination valve bracket back into place. Now that you have it mounted, go ahead and remove the plastic fittings one at a time and re-attach the front and rear brake lines again. And now you're done! Well, not really, but at least the unit is back in place. Now you have to bleed the whole brake system to remove all of the air from the lines that may have entered the system when you made this change. Check out the "Bleeding the Brakes" page for a detail on how to do this. It gets a little complicated with the combination valve, but take your time and everything will work out just fine.