Greetings everyone. This is my first time posting and since I rely on my truck for towing my racecar, I will probably be around some. I probably won't be able to contribute much since I'm not a truck officianodo.

I've searched through many previous threads in order to find an answer to my problem. I've found threads on power steering and threads on brakes, but haven't been able to find one regarding both. Hopefully someone will be able to help me out. I've had pretty good luck with stumping the experts. Please don't let me down. Here is the issue. It may be kinda long, but bear with me.

The issue is that under braking I feel a vibration in the steering wheel. I feel a vibration/resonance in the brake pedal also. Sometimes the steering effort increases like the power steer pump went out. If I shut the truck off and turn it back on, the steering is fine. When the brakes and the steering is the worst, there is a vibration coming from under the hood. It comes from the outermost high pressure hydro boost line (closest to fender).

Here is what I have done to fix it so far.
Rotated the tires. Had front rotors turned. Replaced front pads. Removed/replaced front slide pins. Replaced rear rotors. Replaced rear pads. Removed/replaced rear slide pins. Bled brakes. Had rear ABS sensor replaced.


Could a bad power steering pump or power steering box cause this? Could one of these cause the power steering fluid to airate and throw of the brake power assist? How affective would bleeding PS system be? I am going to check the low pressure inlet to the PS pump for cracks which could cause airation. I do know that the pitman arm rod end is loose, but the brakes seem to shutter even why turning. What about a bad wheel speed sensor?

I haven't driven the truck for several months since I haven't needed to tow anything. Now that racing season is over, it's time to get the ol' girl back into shape.

The truck is a 2000 F250 PS7.3 4X4 CCSB w/ about 130k miles.

Thanks in advance for the help and consideration.

 

Does ABS light come on?

 

Nope. The ABS light used to come on, which is why I replaced the rear ABS sensor and it hasn't come on since. No other lights have come on either. So, I am assuming it hasn't thrown a code.

 

Welcome to FTE!! I have a shudder also and have had the rotors turned and replaced pads... I re-bed the pads in and the shudder went away but is slowly coming back... I think it is because the pads don't have gas escape slots and arent' chamfered, the pad sticks a little, then releases then sticks a little, and repeats causing a shudder... The Ford pads are chamfered and have gas slots built in... As for the steering... my steering is funky too so i can't help you on that one...

 

How long has it been since the hydro/PS fluid has been flushed and changed?

 

I would guess never. I bought it w/ about 85k miles and I never changed it. The pump does have a leak too, but I am not sure where it is coming from. I've topped it off with PS fluid that has stop leak in it. From reading other threads, I've decided to try flushing it and replacing the fluid synthetic ATF. I may replace the low pressure hose too because if it is what is leaking, then the pump could draw air in. There doesn't seem to be the shutter during the first 5 minutes of operation, but eventually shows up. This leads me to believe that it could be an air entrainment issue.

Either the issue is something that will impact the steering and brakes (common like fluid or pump) or I am battling two different issues. Hopefully it's just one simple issue.

 

6ltr - The root cause seems to effect the steering and brakes. (assuming one root cause for both problems) At times I've experienced the vibration in the hydro boost line, resonance when I turn the steering wheel, and a brake pedal that will go the floor. The resonance in the hydro boost line comes and goes. The biggest problem is that it is an intermitant problem. I can't find any consistency.

As far as your brakes are concerned, this is what I learned from my road racing and from books I've read.
1. The slot in the pad isn't used for gassing. It is there for adding another leading edge to the pad. The leading edge of the pad provides a significant amount of "bite". The slot also allows the pad to flex and not crack.
2. Early pad designs were prone to gassing. Today's carbon pads don't do this.
3. I believe the chamfered leading edge is for noise reduction and as a where indicator. This I'm not exactly sure about.

As for the brake shutter coming back, it sounds alot like what I've experienced. It was fine then got worse. Typically what causes the shutter at the brakes is irregular brake material transfer. That could be cause by a number of reasons. Improper bedding procedure, poor quality pads, grease or oil on rotors, or what I think I'm experiencing is a faulty brake system. If the system is not working perfectly, then small pulsations (unnoticable to driver) can create irregularities in the pad transfer. Over time this builds up and becomes a problem. Take a look at your rotors and see if color is irregular or inconsistant. Now that I mention it, I need to do the same thing.

Thanks for the input and maybe this will help your issue. I case you are interested, this HPBook is decent for brake systems. "Brake Systems" by Mavrigian and Carley

 

Hey Guzzle, do you have a write-up on the hydo/PS flush? I would'nt mind doing that myself.

 

I took a few pics he last time I flushed my system but after I was done, the proceedure is almost too simple to do a write-up on.

Disconnect the pump return line, connect a clear hose to it and run it into a bucket.
Start engine.
Pump brakes, turn steering wheel while somebody keeps the pump reservoir full.
When fluid that is going to the bucket starts looking real fresh, your done.

It only takes 3 or 4 qts.

 

Thanks Guzzle, you are an inspiration to us all...at least to me.

 

Well, I replaced the ps pump and it seemed to have helped. But I was wrong. It doesn't seem to shutter as often, but I might be being overly optimistic.

I am now going to look over the brakes for stuck pins and measure the rotor run out. Hopefully one of these will prove to be the culprit.