No Power steering/ Power brakes at high RPM

Scottgf · Nov 16, 2020

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 · Nov 16, 2020

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

Adieu · Nov 16, 2020

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

All 4.6 cars are hydroboost.

Noobz347 · Nov 16, 2020

Under drive the pump.

Adieu · Nov 16, 2020

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).

Scottgf · Nov 16, 2020

Noobz347 said:
Under drive the pump.

MustangIIMatt said:
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???

Adieu · Nov 16, 2020

Scottgf said:
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 · Nov 16, 2020

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 · Nov 18, 2020

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.

The Blurr · May 27, 2025

Scottgf said:
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

Hi Scott. I'm having the very same problem on my 03 mach1. Did you find a solution? Rick Kirby

Noobz347 · May 27, 2025

The Blurr said:
Hi Scott. I'm having the very same problem on my 03 mach1. Did you find a solution? Rick Kirby

Dude hasn't been here in 5 years. You should start your own thread.

No Power steering/ Power brakes at high RPM

Scottgf

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HemiRick

I'd be looking at jacking under the house

Adieu

Easy there, this ain't a dating site.

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

Adieu

Easy there, this ain't a dating site.

Scottgf

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Adieu

Easy there, this ain't a dating site.

Scottgf

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Scottgf

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The Blurr

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Noobz347

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No Power steering/ Power brakes at high RPM

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I'd be looking at jacking under the house

Easy there, this ain't a dating site.

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Easy there, this ain't a dating site.

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Easy there, this ain't a dating site.

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