Any mechanics in the house who know hydrostatic brakes?

[21willys]

My 03 cummins truck is having issues with the brakes acting up. Anybody on here familiar with them?

When you apply the pedal is goes part of the way down and gets hard. Then it releases the pressure and acts like you slam on the brakes. At one point the pedal was even stuck down. This all started when I got the truck stuck and slammed on the brakes a couple times.

 

[kenny c]

not familiar with them but I think you are refering to hydro-boost brakes?

 

[Toad]

Have you checked the power steering fluid or checked for a crimped line?

Toad

 

[Yankee Transplant]

Belt may be slipping do you have steering problems at the same time you mash the brake pedal ?

 

[21willys]

Belt is new and so is power steering pump. Lines aren't crimped or kinked. Fluid is new and full. I changed the pump thinking that the pump may be the issue since I've had 4 others on this truck.

And yes hydro boost brakes.

Keep the ideas coming guys.

 

[von-zipper]

This may sound crazy but could the return spring on your brake petal be broken or come loose? [S

Zipper

 

[Willowbilly3]

My logic is that it's the booster. Bit there must be a test procedure. Those parts are too expensive to just make guesses and throw parts at it.
Here's a pretty good read on the subject
http://www.brakeandfrontend.com/operation-diagnosis-and-repair-of-hydro-boost-power-assist-systems/

 

[Tripper]

My logic is that it's the booster. Bit there must be a test procedure. Those parts are too expensive to just make guesses and throw parts at it.

After reading all the other posts I'd have to agree but no clue on how to test that?!

BoB

 

[christcrusader13]

Sounds like the booster tome, maybe that the diaphragm is collapsing... I had that happen before, do you hear any abnormal air noises when you first apply the brake pedal?

 

[21willys]

It don't have a booster.


I finally got to a shop with a good scanner. They scanned it and said the wheel speed sensor on the passenger front isn't getting a signal. So it's confusing the abs computer. The sensor is new...

 

[sgtpontiac]

No ABS light??

It don't have a booster.


I finally got to a shop with a good scanner. They scanned it and said the wheel speed sensor on the passenger front isn't getting a signal. So it's confusing the abs computer. The sensor is new...

I'd think it would set the abs light...especially with no signal at all...but...if sensor is new then either the wiring to or the abs module itself is bad...I'd be checking for continuity from the connector to the module to rule it out...or maybe the new sensor is junk.....??

 

[21willys]

The abs and brake light are on and have been on. When they tried to clear the code today it came back on instantly. I'm going to change the hub assembly and sensor lead again tomorrow. Hope it works.

 

[christcrusader13]

When I said booster, I was referring to 'hydro-boost' assembly... My error on not using clear terminology....

Sounds like something similar on my buddy's dodge when his BCM Body control module started acting up, but his is a 2013, not sure if it would be the same for yours or not...

 

[21willys]

I changed the wheel bearing assembly and the lead for the wheel speed sensor today. Lights went off but pedal is still not correct IMO.
It appeared the bearing had self distructed and ate the sensor.





When I'm in Dallas next week I'm pretty sure that I'm going to try to trade the truck in on a newer one and possibly a bigger one.

Thanks for all the input guys!