No Power steering/ Power brakes at high RPM

[Scottgf]

Hello all,
I have a 97 Cobra that I do road racing track days. I've been chasing a problem with the power steering and brakes.
At high RPM like 6,100+ I lose power steering and brakes. As soon as it gets below that RPM everything is fine.
I've learned to "drive around" the issue but I would like to fix it so I don't have to worry about it anymore.
The car has a new quick ratio rack, a new pump and I replaced one of the hi pressure lines. I've bleed the system, and zero air is in the system.
Help!!!!

Thanks,
Scott

 

[HemiRick]

is this a hydroboost car, or are the PS and brakes separate?

 

[MustangIIMatt]

is this a hydroboost car, or are the PS and brakes separate?

All 4.6 cars are hydroboost.

 

[Noobz347]

Under drive the pump.

 

[MustangIIMatt]

Under drive the pump.

This is likely the best answer. I'm willing to bet with the RPM being turned, the maximum rated pressure for the pump is being reached and it's bypassing. If this is a new behavior, it could be a bad power steering pressure sensor (if the vehicle is equipped) or a bad valve in the pump or rack if it doesn't have an electronic sensor on the pressure line. If this problem has always existed, under-driving the pump with a larger pulley will likely help (at the expense of steering and brake pedal effort being higher in the paddock and when loading on the trailer).

 

[Scottgf]

Noobz347 said:
Under drive the pump.

This is likely the best answer. I'm willing to bet with the RPM being turned, the maximum rated pressure for the pump is being reached and it's bypassing. If this is a new behavior, it could be a bad power steering pressure sensor (if the vehicle is equipped) or a bad valve in the pump or rack if it doesn't have an electronic sensor on the pressure line. If this problem has always existed, under-driving the pump with a larger pulley will likely help (at the expense of steering and brake pedal effort being higher in the paddock and when loading on the trailer).

Thanks for the responses, please keep 'em coming.
I had thought to maybe underdrive the pump but since that the engines' redline is almost 7k why would the pump stop working at 6,100.
Thoughts???

 

[MustangIIMatt]

Noobz347 said:
Under drive the pump.


Thanks for the responses, please keep 'em coming.
I had thought to maybe underdrive the pump but since that the engines' redline is almost 7k why would the pump stop working at 6,100.
Thoughts???

The same reason A/C compressors cut out around 5,000 or so on most cars, to keep from building too much pressure in the system.

 

[Scottgf]

I understand what you mean but I would hope Ford could design a ps pump to spin to at least redline. Cutting off the ac is one thing but cutting off your steering and brakes at top speed is another. Thanks for the response.

 

[Scottgf]

Does the power steering reservoir have any kind of screen or filter in it? I’m thinking maybe it’s partially blocked restricting the flow.