Will some one explain the difference between a Aisin and a JST brake master cylinder please? I have a 93 4x2 22RE DLX with automatic transmission. I think brake master cylinder has gone bad. Losing fluid but can't find any leaks around the rear wheel cylinders or the front calipers. Thinking it's leaking into the brake booster. Thanks in advance.

 

Now that brake fluid is on the diaphragm in the booster you're going to have to change the booster too. You can get by with swapping the master by itself but the booster will die shortly after.

 

You can pull the nuts off of the master and slide it away from the booster without undoing all the lines to easily confirm your diagnosis, but if you are correct than WT is right, you need to replace both.

The good news is now is the perfect time to hit the yards for a V6 4x4 truck and upgrade both the master and the booster on the cheap.

 

Had to park the truck for a while. I've replace the master cylinder but still having issues with the brakes. I've bled the system until I know there isn't any air in it. I bled the MC before putting it on. However, I can't get it to shift out of park. Brakes lights come on and everything else seems to work as it should. Any help/ides? Thanks

 

I figured out the problem. After taking the dash apart and tracing the wiring and cable from the shifter, I found the cause. The cable from the shift lever pulled through the brake pedal because the little white cap had broken off. So I disconnected it and pulled the cable back out. I can take the truck out of park again. I wrote this up so maybe it will help the next person who has this problem.