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· Registered
12 Posts
Discussion Starter · #1 · (Edited)
OK Im new here and this is the first Diesel Ive owned.
1998 3500 Dually 4X4 with the 24VCummins Turbo Diesel engine.

I bought the truck about 2 weeks ago and the pedal has been hard since I got it... the brakes work and feel like they are getting slight boost, but the pedal is very hard...

In addition to the hard pedal, and the pressure line from the pump to the Hydro is leaking...

I believe these to be related. Im replacing the line after work today, and was wondering if there is a bleeding process to follow to get these brakes to work better or if they are self bleeding... Internet searches have turned up nothing helpful, except finding this site. :D

Any help here is very appreciated, I might not get back to you till later tonight...:help1:

· Registered
12 Posts
Discussion Starter · #3 · (Edited)
This is out of one of my manuals.

The hydraulic booster uses hydraulic pressure from the power steering pump. Before diagnosing a booster problem, first verify the power steering pump is operating properly. Perform the following checks.

•Check the power steering fluid level.
•Check the brake fluid level.
•Check all power steering hoses and lines for leaks and restrictions.
•Check power steering pump pressure.
The hydraulic booster unit will produce certain characteristic booster noises. The noises may occur when the brake pedal is used in a manner not associated with normal braking or driving habits.

A hissing noise may be noticed when above normal brake pedal pressure is applied, 40 lbs. or above. The noise will be more noticeable if the vehicle is not moving. The noise will increase with the brake pedal pressure and an increase of system operating temperature.

A clunk-chatter-clicking may be noticed when the brake pedal is released quickly, after above normal brake pedal pressure is applied 50 - 100 lbs. .

With the engine off depress the brake pedal several times to discharge the accumulator. Then depress the brake pedal using 40 lbs. of force and start the engine. The brake pedal should fall and then push back against your foot. This indicates the booster is operating properly.


1.Start the engine, apply the brakes and turn the steering wheel from lock to lock. This will ensure the accumulator is charged. Turn off the engine and let the vehicle sit for one hour. After one hour there should be at least two power assisted brake application with the engine off. If the system does not retain a charge the booster must be replaced.
2.With the engine off depress the brake pedal several times to discharge the accumulator. Grasp the accumulator and see if it wobbles or turns. If it does the accumulator has lost a gas charge and the booster must be replaced
VERY good info!

This is exactly what I needed.

I have a chatter when the fluid gets low, but when I fill it up everything seems to work OK except the hard pedal and a pull to the right..(I did a few tests today)

The brakes do WORK and they work better when the fliud is full (of course) even the pull improves slightly but still not satisfactory, the pedal is much to hard and high.

This pull leads me to believe that the brakes themselves might need to be bled out a bit, since the visual checks and physical inspections are good.

Once I put this Pressure line on and bleed out the lines in the Hydro I think I may find the issue to be resolved, or need a new HydroBoost...

I have to go out of town till this weekend so the pressure line will have to wait, Ill keep you posted when I get back.


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