98 K2500 brake question

[Bill Miller]

Hi,

I have a '98 Sierra 2500 HD (8 lug) 4x4. Today, the brakes went out. Seemed to be a bad master cylinder. No fluid leaks at the front calipers or the rear wheel cylinders, and plenty of fluid in the resivoir, but the pedal went right to the floor. Took it to my mechanic, and we both felt that it was a bad MC (looked to be original, truck has 145k miles). So, we get a new MC, and bench bleed it. Swap the new MC in for the old one, bleed it, but still no pedal. Won't pump up, and goes right to the floor. We bled all the lines, but still no pedal. My mechanic said that he flet very little pressue when bleeding the lines.

I was wondering if there was possibly something in the ABS unit, or some kind of vavle that could be bad.

Any thoughts/insight on this would be greatly appreciated.

TIA and happy holidays.

[dougo]

Originally Posted by Bill Miller

Hi,

I have a '98 Sierra 2500 HD (8 lug) 4x4. Today, the brakes went out. Seemed to be a bad master cylinder. No fluid leaks at the front calipers or the rear wheel cylinders, and plenty of fluid in the resivoir, but the pedal went right to the floor. Took it to my mechanic, and we both felt that it was a bad MC (looked to be original, truck has 145k miles). So, we get a new MC, and bench bleed it. Swap the new MC in for the old one, bleed it, but still no pedal. Won't pump up, and goes right to the floor. We bled all the lines, but still no pedal. My mechanic said that he flet very little pressue when bleeding the lines.

I was wondering if there was possibly something in the ABS unit, or some kind of vavle that could be bad.

Any thoughts/insight on this would be greatly appreciated.

TIA and happy holidays.

I have the same problem 97 3500 7.4 . have not found the answer
replaced master cylinder two times ,rear brake shoes and wheel cylinders
front pads, front brake lines.blead brake lines several times. save your money.do you have a power brake boster that works of the power steering pump .have you found the problem yet? anyone?