Drum brake junction block?

[kaisermusic]

Anyone tell me the purpose of the stock drum brake junction block? I have all new brake system including lines, master cylinder, drums, valves etc. has been bled properly multiple times but still requires me to pump the pedal a few times before brake pressure builds. No leaks. Someone told me the junction block could be bad and this leads to the failure in pressure. True?

 

[Broncobowsher]

the block is nothing more then a pressure differential switch. If one half of the brakes goes out that side will have less pressure. The different pressures are suppose to move an internal valve and ground the wire going to it. This turns on the big red "brake" warning light on the dash.

The usual mode of failure is corrosion jamming the valve in the middle or leaks.

If you have to pump the brakes the first thing I would check is the adjuster working correctly. Takes a few pumps to push the shoes out. After sitting the retractor springs pull the shoes in and you have to pump again. Go too far and you will blow a wheel seal and you will no long be able to pump up at all (no brakes).