No Power steering/ Power brakes at high RPM

Scottgf

Member
Nov 28, 2017
9
1
13
Southern California
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
 
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MustangIIMatt

I need something stupid to play with
Mod Dude
Mar 7, 2002
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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

Member
Nov 28, 2017
9
1
13
Southern California
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

I need something stupid to play with
Mod Dude
Mar 7, 2002
8,777
4,506
224
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

Member
Nov 28, 2017
9
1
13
Southern California
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. :)