M1009 Hydro boost

[kipman]

What are the symptoms of a hydro boost going bad? my 1009 brakes were working great, once in a while the brake light would come on, the pedal was about half of normal, and took more effort to stop the truck, pump the pedal one time, back to normal, it did this a few times over the last 2 years, now the light is on, pumping the brakes does not help, master cylinder is full. no leaks that I can find.

 

[GoinNutts]

When you say pump the pedal do you mean the pedal goes to the floor or the pedal is high like the truck was not running? If pedal goes to floor and pumping brings pedal up it means air in the lines. If the pedal is high and stiff and acts like the truck is not running check PS fluid be sure it is full and all the hoses are good. Email diagnostics are hard good luck

 

[kipman]

All fluids are good, not to the floor,the more I think about it, it most likely is the Master cylinder, thanks for the reply.

 

[ranchhopper]

Usual signs of a hydroboost going out is a stream of power steering fluid running down the floor mat on the drivers side.

 

[kipman]

 

[Bolt]

Low Brake Pedal

The seals in the master cylinder won't seal against the pitted bore. Water got in over the years, sank to the bottom of the bore and rusted creating an uneven surface for the seals to seal against. They may work ok when you hit the pedal hard, but the pedal might sink when applied slowly. You were correct, it's a master cylinder problem.

 

[kipman]

Thank you, she gets a new one tomorrow.