Engine Gets Hot -brakes Lock Up

[mvance1944]

I have just 50 miles on my fresh restoration of my '52 dodge B3B p/u.

As the engine temp. warms up, so does the brake fluid in the master cylinder which causes the brakes to lock up and all the free travel in the brake pedal

disapears. The brake light comes on and stays on until the brake fluid cools down. I keep adjusting the brake piston rod between the master cylinder and brake pedal hoping to solve the problem. The master cylinder, brake cylinders and brake shoes are all new. My question is, is this a normal condition, and am I doing the right thing to correct the problem, or do I have a problem somewhere in the brake system that needs to be corrected? I don't know much about this type of brake system so any advice would be appreciated.

Thanks guys!

Mike V.

[Dodgeb4ya]

M/Cyl. piston might not be returning to the end stop oval washer so the relief port is always covered up. With the engine warming the M/C piston is even slower to return.I've had this happen a few times over the years on the old MoPars. The M/C bore clearance and finish has to be correct. I found this problem by pulling the M/C rubberboot back and seeing that the piston would not freely return back all the way therefore I could not adjust for correct freeplay!

[MBF]

I agree w DbY4A. Check the master cyl bore and overhaul if necessary making sure the check valve asm is right. Another item you may want to check are the flex hoses. As these age they can collapse internally restricting the return flow of fluid after the brakes release and cause them to drag. I try to flush the systems in my old stuff every year or so due to the fact that DOT3 is like a wick for moisture. Mike

[Merle Coggins]

First thought I had was that the M/C fill cap breather may be plugged. If it can't breath the heat will cause a raise in the internal pressure, which can't escape.

Also as mentioned, check that the piston returns fully and that the port in the bottom of the reservoir is not plugged.

Merle

[123.gramps]

'Morning all. Happened to me several weeks ago. Found the master cyl return adjustment was incorrect and "bleed hole" was plugged. Each time brakes were used, peddal came up harder and harder. Managed to get it home but brakes and engine were hot.