Mechanics

CHANGED FRT BRK PADS NOW PEDEL SEEMS TO HAVE TO MUCH TRAVEL ON 1ST PUSH THEN FEELE NORM ON SEC.SHIMS R ON PADS

2006 Hummer H3 • 91,000 miles

When you put in reverse pedel seems fine then in drive after 1st time you apply brakes after that pedel goes about half way then pump once pedel at top good braking all the time just the feel of the pedel on 1st pump
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Jay's repair
January 23, 2012.




That's a sign the rear drum brakes are not adjusted up fully. Pumping the pedal pushes the shoes out part way. They take some time to retract so they're already partially applied when you press the pedal the second time. The clue is once you get a good pedal from pumping it up, it will be too low again after leaving it released more than a few seconds. Rusted star wheel adjusters, worn teeth on an adjuster, and parking brake cables stuck partially applied can prevent automatic adjusting from taking place.

Caradiodoc
Jan 23, 2012.
Has disc brks in rear tht r almost new
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Tiny
Jay's repair
Jan 23, 2012.
Is the parking brake built into the calipers?

Caradiodoc
Jan 23, 2012.
Don't know pro& cons

Tiny
Jay's repair
Jan 23, 2012.
If there's a spring-loaded lever on the back of each rear caliper, those pistons will not adjust out from just pumping the brake pedal like the front ones will. You have to work the parking brake to adjust them. Until you do that, the pedal will be too low.

If the parking brake cables are rusted tight, you can operate the levers on the calipers with a channel lock pliers. Those cables shouldn't be rusted tight yet though on a five-year-old vehicle.

Caradiodoc
Jan 23, 2012.
Just one more? Pedel was surrposably fine until I change frt pads says owner

Tiny
Jay's repair
Jan 23, 2012.
I guess I would remove the two front wheels, then watch what's happening when a helper pushes the brake pedal. Be sure the calipers' slides are free of rust and dirt and are coated with high-temperature brake grease. If one caliper doesn't apply, look if there are four steel lines coming out of the master cylinder. That's normally a front-wheel-drive car thing, but if you have that, you have a split-diagonal hydraulic system. There is a valve that trips and blocks fluid flow to one front wheel and the opposite rear one. That valve trips from pushing the brake pedal more than half way to the floor after installing new pads. Pushing the pedal that far must never be done on a GM vehicle or on any other brand that is more than about a year old. Besides that valve on GMs, crud and corrosion build up in the bottoms of the bores where the pistons don't normally travel. Pressing the brake pedal more than half way down runs the lip seals over that corrosion and can tear them. If both front brakes are applying, you don't have to worry about whether that system is used or if that valve tripped.

Also check the rubber bladder seal under the reservoir cap. If it is blown up and mushy, the brake fluid is contaminated with a petroleum product. A slight residue of engine oil or wheel bearing grease on your fingers when you reset that seal into the cap is enough to cause problems. Fixing that is real expensive, especially if the vehicle has anti-lock brakes.

If the low pedal only occurs while driving, and not while on the hoist, check for a sloppy wheel bearing. That will allow the rotor to wobble and push the piston back into the caliper. On the next brake application, the pedal will have to travel further to push the piston back out. If it stays there, the second pedal application will feel normal.

Use a dial indicator to measure rotor runout. If a warp was machined in accidentally on the brake lathe, you may not feel that while driving and braking but it could be enough to push a piston back into the caliper. You're looking for sideways runout, not thickness variation.

Caradiodoc
Jan 23, 2012.
It has a n1 brk master on it the problem I'm having related to it

Tiny
Jay's repair
Jan 24, 2012.
Don't know what that means. What's a n1?

Caradiodoc
Jan 24, 2012.
When I went to a gm site this is what it showed for a master brake cylinder it's electric so I didn't know if there was something special you were to do when changing brk pads

Tiny
Jay's repair
Jan 24, 2012.

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