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Author Topic: low brake pedal  (Read 1866 times)

cumminsguy

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low brake pedal
« on: January 13, 2016, 02:59:29 PM »

My "newest" 98 HD 4x4 (Monroe)has a low brake pedal or (long travel).The truck stops fine once it reaches "the spot". I notice fluid movement in the master@ about 1 inch of pedal travel. I bought the truck with new hydroboost, master, and p/s pump hoses and box. I have replaced everything else that was needed minus front calipers(there ok). I had wheel speed sensor codes up front and traced it to the controller, I then replaced it with a known good controller. The pedal has felt the same as when I brought it home. What am I missing? The only thing I did not try was to bleed the ABS controller. I have even replacesd the master again just because. Still no change. Any help will be great.
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RPF207

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Re: low brake pedal
« Reply #1 on: January 13, 2016, 05:43:27 PM »

So this Monroe Dana 70 front has ABS?
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1999 chevy HD 4x4 135.5" 6.5 nv4500 bw4470 Dana 70 HP 10 lug front

Due to recent budget cuts the light at the end of the tunnel has been turned off

ED-NY

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Re: low brake pedal
« Reply #2 on: January 14, 2016, 09:00:12 AM »

Stuck caliper?

Try holding each caliper (careful not to get pinched) and have someone push on the pedal. Sometimes you can feel the caliper shift instead of slide indicating a stuck or crooked piston. Used this method with calipers that have pistons on both sides..but detecting a stuck single piston caliper this way should work. 

Hopefully one of the calipers movement should feel different from the other three.
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cumminsguy

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Re: low brake pedal
« Reply #3 on: January 14, 2016, 10:54:06 AM »

Rear calipers are new and there are no problems with the front. Yes Dana 70 with abs.
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Raymo

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Re: low brake pedal
« Reply #4 on: January 14, 2016, 11:04:02 AM »

One of the 300 times I was going to burn my truck to the ground, was bleeding the brakes trying to get a good pedal. That was, until I bought a power bleeder. Put adapter on reservoir, fill with fluid, pump to 10psi and open the bleeders.

That said, I'm going to try the NBS master cylinder at some point, but read hydroboost may need some work to the housing.
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'94 3500-HD, Cummins, Getrag, NP205. Shortend rear frame with a Pickup Bed. Dana 60 front, stock 80 rear.

'03 2500-HD 8.1 and Allison

cumminsguy

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Re: low brake pedal
« Reply #5 on: January 18, 2016, 08:23:39 PM »

Well, found the problem. The hydroboost was the wrong. Replaced it with the correct one and now the pedal is were it should be and the truck stops great. Thanks for everones input.
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ED-NY

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Re: low brake pedal
« Reply #6 on: January 18, 2016, 11:18:38 PM »

Well, found the problem. The hydroboost was the wrong. Replaced it with the correct one and now the pedal is were it should be and the truck stops great. Thanks for everones input.


Have any idea what the difference was? Bore - stroke ?
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cumminsguy

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Re: low brake pedal
« Reply #7 on: January 19, 2016, 12:36:06 PM »

Physically the unit looks the same externally. The bore is the same, the depth to the piston(or cup)is the same but the difference is in the depth of the "dish" of the cup in its center, which was about 1/4''. I am thinking that I had a hydroboost from a 3500 or 2500? The replacement unit I bought was from NAPA and was told there is only one listing for the 3500HD.
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ED-NY

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Re: low brake pedal
« Reply #8 on: January 19, 2016, 03:25:10 PM »

Cumminsguy

Just asked because I just put a 3500HD together from a collection of parts I have. The cab was a K2500 vacuum brake unit and I installed a hydro-boost from a 92-95 3500HD. Just got it running today...should be good to go with the proper 3500HD brake setup.

Thanks
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