Poor brakes. Suspect booster or master cylinder?

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Poor brakes. Suspect booster or master cylinder?

Postby TRACTJDS0428 » Fri Nov 21, 2014 6:10 pm

The truck set for a while during restoration. Back driving it and noticed the brakes arent what they used to be. Feels like very little or no rear brakes. New shoes and wheels cylinders a few years ago. Adjustment seems ok. Front rotors are now warped. Very spongy pedal. Very little resistance till half way down. Tried bleeding and the fronts bled great. Started bleeding at the anti-lock block in the rear because I could hear obvious air in the line when the pedal was pumped. Got a lot of air out of it. No visible leaks. Pedal felt better for a minute or so then back down to halfway before resistance. Pump the pedal 4 good times and the air is gone and brakes are good. Driving i can pump the pedal 4 good times and the brakes grab noticably harder and alot more feel from the rear brakes. My first thought was the booster or internal master cylinder failure. But then remember another dodge guy telling me about definite master cylinder issues with these trucks. Also thought about eliminating the anti-lock as it doesnt function. So what are your guys thoughts.
1993 Dodge W250, Cold Air, Borg Warner 60/68 turbo. 4" down pipe. 5x14 Injectors. Pump Mods. Airdogg II 165, Billet Fuel Tank Sump. ATS valve body, ATS converter, Pyro, Fuel pressure, Boost and Trany temp gauges. 72" T-Rex Products Long Bars. 285/75-16 Toyo Open Country M/T's. Western 9Ft MVP Ultra Mount V-Plow.
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Re: Poor brakes. Suspect booster or master cylinder?

Postby ellis93 » Fri Nov 21, 2014 6:36 pm

No signs of a leaking wheel cylinder? Disappearing/reappearing air is usually sign of that.
93 D250 ,5 speed,4.11s,k&n autometer tach pyro trans boost guages,GDS 60mm h1c 14cm,honed 5x10,hplp/reg,1/8 timing,M+H M2 fuel pin, tims cooler tubz
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Re: Poor brakes. Suspect booster or master cylinder?

Postby PToombs » Fri Nov 21, 2014 6:37 pm

Sounds like the ABS valve in the back crapped out due to the fact you bled it and it was ok for a minute. Remove it and run the line direct to the hose, then unplug the brain box behind the glove box. Some guys never have problems with their ABS but most of us do. I deleted mine and the truck stops great, straight and even. Good pedal too.
pete

Just enough power to break everything behind the crankshaft.
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Re: Poor brakes. Suspect booster or master cylinder?

Postby TRACTJDS0428 » Sat Nov 29, 2014 10:52 am

No signs of leaking. No fine mist. Checked all connections with cardboard for a high pressure leak.
1993 Dodge W250, Cold Air, Borg Warner 60/68 turbo. 4" down pipe. 5x14 Injectors. Pump Mods. Airdogg II 165, Billet Fuel Tank Sump. ATS valve body, ATS converter, Pyro, Fuel pressure, Boost and Trany temp gauges. 72" T-Rex Products Long Bars. 285/75-16 Toyo Open Country M/T's. Western 9Ft MVP Ultra Mount V-Plow.
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Re: Poor brakes. Suspect booster or master cylinder?

Postby TRACTJDS0428 » Sat Nov 29, 2014 10:57 am

PToombs wrote:Sounds like the ABS valve in the back crapped out due to the fact you bled it and it was ok for a minute. Remove it and run the line direct to the hose, then unplug the brain box behind the glove box. Some guys never have problems with their ABS but most of us do. I deleted mine and the truck stops great, straight and even. Good pedal too.

The problem was there before I bled it. Literally sat for a couple months and pedal went to sthi. Makes no sense without a leak. It almost acts like the back is under vaccum and pulling air from somwhere. Good hard pedal after 4 pumps. Wait 30 seconds and it goes almost to the floor with little or no rear brakes. I can hear air in the anti lock valve so I will bypass it for sure to start.
1993 Dodge W250, Cold Air, Borg Warner 60/68 turbo. 4" down pipe. 5x14 Injectors. Pump Mods. Airdogg II 165, Billet Fuel Tank Sump. ATS valve body, ATS converter, Pyro, Fuel pressure, Boost and Trany temp gauges. 72" T-Rex Products Long Bars. 285/75-16 Toyo Open Country M/T's. Western 9Ft MVP Ultra Mount V-Plow.
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Re: Poor brakes. Suspect booster or master cylinder?

Postby oldestof11 » Sat Nov 29, 2014 3:50 pm

Sounds like the ABS module then.
Jon
93 D250~ Mismatch of cheap parts, trying to look fast going slow
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