GMC c1500 -83 rear brake drums

[Swed-Chevy]

Hi , i was showing the truck at our two year check for safety things like brakes and it showed that left rear brake was poor. Last time they checked this the brakes was just fine and they approved the truck for driving.

https://www.mynewsdesk.com/se/opusbi...en-del-4-47583

Adjusted the rear brakes and should bleed the fluid but in the left wheel cylinder there was no fluid at all , we must pump the brake pedal several times to get fluid coming out of the bleed nipple. Can not see any leakage anywere so
this was strange , have never seen this before.

Checking level in the fluid cannister at the mastercylinger often. We bleed both rear drumbrakes but still poor ( uneven )brakes .

Any tip about this would be great.

[Dead Parrot]

Possible enough rust and/or debris is in the metal line to restrict fluid flow.

How old is the rear hose? Maybe it is failing inside and pieces are plugging the T-joint outlet to the left.

[geezer#99]

Is the proportioning valve tripped?

[Swed-Chevy]

Thanks for tip , should check this and also replace the rear hose and clean
the brakelines.Maybe i could put on the drums and blow air thru the bleeding
nipple when the hose mountings are loose.

After all bleeding on the rear brakes and i should drive it the brake light in the dash
came on directly when ignition was on but went out when i pushed the brakepedal
so maybe the proportioning valve should work ?