Ron68 wrote:

The 92 Ranger had disc/drum brakes. The master cylinder has a residual pressure valve to keep slight pressure applied to the rear drums so that they don't have to move very far to be applied. If you hook up disc brakes to a master cylinder for rear drum brakes the discs will not fully release.

 
Can I remove the residual valve or do I need to replace the mc?

MS wrote:

I have been using the 92 Ranger MC on my car with four wheel discs for about 15 years now without any problems. I doubt the MC is the problem.
Try removing the big nut under the adjusting knob on the prop valve to see if the brakes unlock.

I figure you already have new hoses and steel lines. Check for dents in tubing, old hoses that are swollen internally or parking brake cable adjusted too tight.  Even an internally misformed tube flare can close shut when a bubble flare is overtightened.

And check the banjo bolts for fluid clearance if you do not have Ford originals.

 
So there is no residual pressure valve in the ranger mc? I had this problem with the rear drum brakes and this mc. The mc I had on it before was from a 67 mustang. Everything worked great. Since then I've changed the prop valve to a Wilwood adjustable, replace the hose to the axle and the rear caliper hoses. I've thought about putting the 67 mc back on but I'm not sure how it will work with rear disc.

Have you checked pushrod clearance since you changed out the master?  The symptoms don't line up exactly but if your master is not retracting because the pushrod is too long it can cause pressure to build up in a circuit and lock the brakes.  I think it is more common for this to happen on the fronts but never say never.  A quick check if it happens again on a test drive is to loosen the M/C mounting nuts a turn or two if they lock up again.  If the brakes release then look to the pushrod.  Better yet, check clearance first and then test.

Well I checked the part number on the invoice with the Summit on line catalog and that part number does not appear anywhere so I'm going to assume I have the wrong mc. I'm replacing it with a 2000 v6 mc and replumbing it all. Also can anyone tell me how to readjust the e-brake ?

tweet66 wrote:

Don't forget to check the rear brake hose. Had a similar problem few years back where the rear brakes keep locking up. Replaced everything in the brake system except the flexible hose, turns out I had a small flap of rubber inside the hose that would allow the fluid to go to the brakes but not return.

 
That was the first part I replaced.