front disc brake lockup

[vargaspj]

Thanks everyone for all the help!!! Very thoughtful ideas and suggestions.
I replaced the 3 front flexible brake line hoses with new from Vintage Power Wagon. The ones I replaced all seemed to be old but still solid (they didn't look like they had been collapsing).
I looked at the MC (Master Cylinder) pushrod and it was tight with no play.
After reading all the previous posts I plan on bleeding the system and re-adjusting the MC pushrod so it's not tight at rest.
I've got my fingers crossed.
At the very least I've got 3 new flex lines on the front.
The new MC is from Antelope Valley Equipment & Truck Parts here in California.
Will post if this fixes the problem.
Again, much thanks. The people in this hobby are a very good group.
P

[MSeriesRebuild]

The reason I ask where the MC came from; a vendor has been putting out some bad ones for a while now. The issue is with the check valve, but yours came from a different place, I haven't heard of any issues fom Antelope Valley parts.

If you had no free travel at all in the pedal, I feel like you have nailed the issue, as that will cause the brakes not to release, and the hotter they get, the tighter they get until they lock down as you described. Get just a slight amount of pedal free travel, what the book says is actually more than is necessary. If you can bleed the system using a pressure bleeder, that does the best job. Most likely you will be good to go.