Brakes Dragging After New Brake Booster and Master Cylinder

[shermancelmare]

93 XJ 4.0L. I swapped the old master cylinder and booster with a new one from a '96 XJ. Now, the brakes begin to drag after it is warmed up (say, after 10 minutes of driving). Smoke coming from front wheels is never a good sign. One it cools down, the drag goes away.

The master cylinder is not overfilled. Could the brake booster push rod need to be adjusted? If so, how is this done?

[rhandwor]

Originally Posted by shermancelmare

93 XJ 4.0L. I swapped the old master cylinder and booster with a new one from a '96 XJ. Now, the brakes begin to drag after it is warmed up (say, after 10 minutes of driving). Smoke coming from front wheels is never a good sign. One it cools down, the drag goes away.

The master cylinder is not overfilled. Could the brake booster push rod need to be adjusted? If so, how is this done?

Use a straight edge flat against the flange and measure the length of the rod to the tip.
Measure the old one the same way. On the old ones the rod was threaded and I used a pair of channel locks. Any way record the length in case you have a hose collapsed going to the calipers. Normally getting a set that was working on the old vehicle isn't a problem was the gasket installed between the booster and flange.

[djhughes]

Im a new guy here, and have a lot to learn, but yes it sounds like the push rod is out of adjustment, and the vent port in the master is blocked, when the brake fluid heats up it expands and has nowhere to go except push the caliper pistons out.

[DeltaP]

The brakes are dragging and all the advice is good. But first check and see if the "new" booster/master is compatible with your jeeps year.