Brake issue ... dragging pads and pedal sinks

BodhiBenz1987 · **Posted:** Sat May 02, 2009 7:29 pm

Hey guys, coming out of lurk mode to ask a brake question. My CRD has a brake issue that I don't quite understand and would prefer not to leave entirely to the dealer.
The symptoms: The brakes drag noticeably (although not to the point where the wheels get unusually hot) when no pressure is applied to the pedal ... I can hear the faint drag at pretty much all speeds. They make an awful scrapping noise when I apply the brakes. The other symptom: Brake pedal sinks to the floor slowly.
What I've checked:
-I removed each wheel and inspected the rotors, pads and calipers. All pads looked normally and evenly worn, no foreign objects stuck in the brake parts. Rotors look ugly but not anywhere near bad enough to warrant this. Calipers looks OK and the pistons will move back slightly when pressed upon. I removed each pad, cleaned out the pad carriers and puts the pads back in place. There is no fluid leaking anywhere externally. Hoses look fine, master cylinder remains full.
-I inspected all hoses to and from the booster, no leaks that I can detect, but I do not have a MityVac so not positive a leak doesn't exist.
-I went through the procedure for checking for master cylinder internal leak/booster failure. Pedal holds firm with engine off in neutral. It slowly pulls downward when engine is started. However, in any mode, when I pump the pedal, I can hear a wheezing sound ... like a squeak toy with no squeaker. When I pump the pedal with the engine running, it builds pressure but really sinks hard to the floor with continued foot pressure.
So ... 1) How are the pads dragging and the pedal sinking related? 2) Would doing a brake flush achieve anything? 3) Does this sound like it might be a vacuum leak and worth buying a MityVac to continue tests?
Thanks ...

tjkj2002 · **Posted:** Sat May 02, 2009 9:44 pm

Right from the '05 FSM..................

PEDAL FALLS AWAY
A brake pedal that falls away under steady foot
pressure is generally the result of a system leak. The
leak point could be at a brake line, fitting, hose, or
caliper. If leakage is severe, fluid will be evident at
or around the leaking component.
Internal leakage (seal by-pass) in the master cylinder
caused by worn or damaged piston cups, may
also be the problem cause.
An internal leak in the ABS or junction block may
also be the problem with no physical evidence.

BRAKE DRAG
Brake drag occurs when the lining is in constant
contact with the rotor or drum. Drag can occur at one
wheel, all wheels, fronts only, or rears only.
Drag is a product of incomplete brake shoe release.
Drag can be minor or severe enough to overheat the
linings, rotors and drums.
Minor drag will usually cause slight surface charring
of the lining. It can also generate hard spots in
rotors and drums from the overheat-cool down process.
In most cases, the rotors, drums, wheels and
tires are quite warm to the touch after the vehicle is
stopped.
Severe drag can char the brake lining all the way
through. It can also distort and score rotors and
drums to the point of replacement. The wheels, tires
and brake components will be extremely hot. In
severe cases, the lining may generate smoke as it
chars from overheating.
Common causes of brake drag are:
² Seized or improperly adjusted parking brake
cables.
² Loose/worn wheel bearing.
² Seized caliper piston.
² Caliper binding on corroded bushings or rusted
slide surfaces.
² Loose caliper mounting.
² Drum parking brake shoes binding on worn/
damaged support plates.
² Mis-assembled components.
² Long booster output rod.
If brake drag occurs at all wheels, the problem
may be related to a blocked master cylinder return
port, or faulty power booster (binds-does not release).

BodhiBenz1987 · **Posted:** Sat May 02, 2009 9:58 pm

tjkj2002 wrote:

If brake drag occurs at all wheels, the problem
may be related to a blocked master cylinder return
port, or faulty power booster (binds-does not release).

This sounds like what's occurring (sounds/feels like it's all four wheels), and it jibes with the pedal behavior. Thanks for the info. An FSM is a beautiful thing ...

What does checking return ports on the master cylinder involve? Guess I should get a MityVac, too ... need one anyway.

BodhiBenz1987 · **Posted:** Fri May 08, 2009 6:48 pm

Can anyone tell me how to remove the brake booster check valve? It looks like it can just be pulled out, but I don't want to break it if that's not the case.

Brake issue ... dragging pads and pedal sinks

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