Chev/GMC brake question

I have a 94 GMC 4x4 1/2 ton Sierra with a soft or mushy brake pedal. My older 84 GMC was the same way. I tried everything with it to stiffen up the
pedal but no go. I've been reading that this is "normal" for the GMC. And has been corrected on later models. Does anyone know if is actually "normal" and if there is any after market correction for it? I thought I remember reading that you can install larger calipers (with a slight modification, grinding down a boss or something ) that helps, any info on that? Thanks.JS
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Soft feeling brakes are not normal - it wasn't on my 1988 C1500 (190,000+ miles), my 1995 C1500 (170,000+ miles), nor my current 2004 2500HD. There are several probable causes, all of which can be fixed.
1. Bad master cylinder. The only real solution is to replace it. 2. Air in your brake lines. You will need to have your brakes bled, but be sure that the ABS module is bled also (frequently overlooked). If you do it yourself, start from the closest bleeder valve to the reservoir and working out - ABS module, left front, right front, left rear, right rear. 3. A weak or "soft" brake line. A soft or damaged brake line that connects from the hard piping to each caliper/drum will expand under pressure and cause the spongy feeling. If this is it then consider changing to braided stainless steel lines. 4. A leak. But you would notice the brake fluid in the reservior dropping over a short period.
I'm sure there might be one or two other things, but these are what I've found to be most common.
Cheers - Jonathan

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Bleed, Bleed, Bleed.
As instructed by the shop manual.
You may need to bleed out 2-4 quarts to clear the lines. Some other advice is to get the ABS bleeder tool, it cycles the pumps. Another option is to take it for a drive and lock up the breaks to trigger the ABS a few times, then bleed out the system again. I havent tried this but cause after bleeding 2 quarts I was happy with the results.
Another idea I'm toying with is to get the ABS to test itself repeatedly. This happens at 2-5mph after a start.
Cheers

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My 1983 Suburban had mushy brakes, which I wrongly thought was just the nature of the beast until I noticed that the brake master cylinder was going bad. Its being replaced now; Ill let you know if that fixes it.
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Warren Post
Santa Rosa de Copn, Honduras
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Master cylinder replaced. Now my 83 Suburbans brakes are nice and firm. Hope your Sierra is as easily fixed.
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Warren Post
Santa Rosa de Copn, Honduras
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I`m not sure about the older ones,but my '97 brakes sucked.GM tried to save a few bucks back then and put smaller rotors on.Also the back brakes come out of adjustment alot. I had a good friend take it in to Chevrolet for me and replaced everything from master cylinder to rear brakes. No change.
P.S. The brakes on the HD's are 4 wheel disc.So of course there gonna be fine.
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Bill wrote:

Also the front rotors were thin and tended to heat warp....
The 99 & up new body style Chevys were advertised as thick rotors..
Also the back

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The only problem I ever had with the front rotors of both my '88 and my '95 Chevy's were from over-torquing the lug nuts when the wheels were put on every time they were rebalanced and rotated. If I let the guy doing the work tighten them with an impact wrench or if he hand torqued them to 100 ft-lbs (the recommended torque per the book) then the front rotors would warp within 3000 miles. If however I insisted that the lugnuts be hand-tightened to only 90 ft-lbs max then I had no problems for the next 10,000 miles until the tires got balanced and rotated again. Whe I replaced the front rotors on my '88 with an aftermarket brand, the same problem persisted, and the same remedy worked. And heaven knows I put enough miles on both of those trucks to know.
Cheers - Jonathan

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"Jonathan Race1" wrote: > The only problem I ever had with the front rotors of both my > '88 and my '95 > Chevy's were from over-torquing the lug nuts when the wheels > were put on > every time they were rebalanced and rotated. If I let the guy > doing the > work tighten them with an impact wrench or if he hand torqued > them to 100 > ft-lbs (the recommended torque per the book) then the front > rotors would > warp within 3000 miles. If however I insisted that the > lugnuts be > hand-tightened to only 90 ft-lbs max then I had no problems > for the next > 10,000 miles until the tires got balanced and rotated again. > Whe I replaced > the front rotors on my '88 with an aftermarket brand, the same > problem > persisted, and the same remedy worked. And heaven knows I put > enough miles > on both of those trucks to know. > > Cheers - Jonathan >
> > > > > > > Bill wrote: > &nbsp;>> > &nbsp;>> I`m not sure about the older ones,but my '97 brakes > sucked.GM tried to > &nbsp;>> save a few bucks back then and put smaller rotors on. > > > > Also the front rotors were thin and tended to heat > warp.... > > > > The 99 & up new body style Chevys were advertised as thick > rotors.. > > > > > > > > Also the back > &nbsp;>> brakes come out of adjustment alot. > &nbsp;>> I had a good friend take it in to Chevrolet > &nbsp;>> for me and replaced everything from master cylinder > to rear brakes. > &nbsp;>> No change. > &nbsp;>> > &nbsp;>> P.S. The brakes on the HD's are 4 wheel disc.So of > course there gonna be > &nbsp;>> fine.
2004 2500HD crew cab at work needed new rear discs at 12000 miles. They were chewed up too much to turn.
The dealer put mud flaps in front of the rear tires. They claim running on county roads got rocks and sand in them and caused them to wear.
It seems like mud flaps behind the front tires would work.
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Not only are the brakes on my 2500HD 4 wheel disc, but they are HUGE.
Interestingly enough, I think the '99-'04 half-ton models also had 4 wheel disc brakes, but Chevy went back to rear drums in 2005 on the half-ton's only with 6-lug wheels.
Cheers - Jonathan
Snip

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