The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 47-55.1 Bad fitting?

dsraven · 01-01-2021, 11:43 AM

The pedal feels sloppy. To make the back rotors stop I am literally holding the pedal down w all I can. Pumping doesn’t seem to help when running. Tried bleeding w it running too and no luck.

seems like you should start at the pedal and work your way through the whole system. ensue the parts are tight, the adjustments are within specs, nothing is binding, etc.
-check the pedal free play
-pedal travel upper stop bumper
-master cyl pushrod end play on the pedal pushrod and also the booster to master cyl
-any and all linkages in the brake pedal to booster to master cyl. is you booster on the firewall or frame?
-check when running, and again when not running and after a few pumps of the pedal to release any stored vacuum in the booter, if there is a small fountain of fluid that can be seen in the master res when the brakes are released after a full hard brake application. there should be 2 fountains actually, one from the front brake circuit and one from the rear. that would let you know if the master is returning fully on both circuits so you know if the circuits are also able to pick up a full shot of fluid for their next application. possibly the booster is moving the pedal pushrod forward when the engine is running so the refill ports in the master cyl are not able to pick up a full charge f fluid.
-do some brake booster diagnostics.
engine off, step on the brakes a coupe of times, use moderate pedal pressure. the vacuum stored in the booster should give you 2 normal feeling applications and then the pedal should start to feel like a non power brake would feel. if less than 2 applications leaves the pedal feeling hard you may have a vacuum leak to deal with.
check the vacuum at the booster, it should be what the vacuum is at the manifold connection. usually this will be around 15-20 inches mercury on the vac gauge. check the hose and the check valve and grommet at the booster plug in. if you have a long hose, like a frame mounted booster, ensure the hose is free of kinks and/or mechanical damage for it's entire length.
once the vacuum is purged from the booster, engine off, step on the brake pedal and hold a moderate application pressure. start the engine while holding the pressure. the pedal should drop slightly.

01-01-2021, 11:43 AM	#20
dsraven Registered User Join Date: Nov 2010 Location: calgary alberta Posts: 8,093	Re: Bad fitting? The pedal feels sloppy. To make the back rotors stop I am literally holding the pedal down w all I can. Pumping doesn’t seem to help when running. Tried bleeding w it running too and no luck. seems like you should start at the pedal and work your way through the whole system. ensue the parts are tight, the adjustments are within specs, nothing is binding, etc. -check the pedal free play -pedal travel upper stop bumper -master cyl pushrod end play on the pedal pushrod and also the booster to master cyl -any and all linkages in the brake pedal to booster to master cyl. is you booster on the firewall or frame? -check when running, and again when not running and after a few pumps of the pedal to release any stored vacuum in the booter, if there is a small fountain of fluid that can be seen in the master res when the brakes are released after a full hard brake application. there should be 2 fountains actually, one from the front brake circuit and one from the rear. that would let you know if the master is returning fully on both circuits so you know if the circuits are also able to pick up a full shot of fluid for their next application. possibly the booster is moving the pedal pushrod forward when the engine is running so the refill ports in the master cyl are not able to pick up a full charge f fluid. -do some brake booster diagnostics. engine off, step on the brakes a coupe of times, use moderate pedal pressure. the vacuum stored in the booster should give you 2 normal feeling applications and then the pedal should start to feel like a non power brake would feel. if less than 2 applications leaves the pedal feeling hard you may have a vacuum leak to deal with. check the vacuum at the booster, it should be what the vacuum is at the manifold connection. usually this will be around 15-20 inches mercury on the vac gauge. check the hose and the check valve and grommet at the booster plug in. if you have a long hose, like a frame mounted booster, ensure the hose is free of kinks and/or mechanical damage for it's entire length. once the vacuum is purged from the booster, engine off, step on the brake pedal and hold a moderate application pressure. start the engine while holding the pressure. the pedal should drop slightly.