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2008 Mustang Gt - No Steering at High RPM

1187 Views 5 Replies 5 Participants Last post by  MasterX
I have a 2008 Mustang GT that has been turned into an SCCA T3 Racecar. Took it to it's first test day, and first session the car ran flawlessly. Second session, the car developed a power steering issue at high RPM. Anything below ~4800RPM, and the power steering works fine. Anything above ~4800RPM, and the steering cuts out completely. It doesn't just lose power steering, but goes into complete steering lock. Steering resumes once the car drops back down in RPM. The rack, pump and lines were original with about 35,000 miles on them. Flushed the system a dozen times, and replaced the pump, but the problem persists.

Any ideas?
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I wonder if the PS fluid is overheating and producing bubbles that cause cavitation in the return line.
You might need to either use a PS fluid that has a higher boiling point, or add a PS fluid cooler. Also check that the hoses aren't collapsing or that air isn't getting through any seals.
that is kind of spooky, and almost sounds mechanical, I wonder if there is a loose motor mount allowing the motor or something else to contact and "pin" the steering linkage in place. Definitely something to get figured out before your next run.
wow, it's hard to imagine something worse that could happen on a track at high speed . . .

I don't know all the inner workings of the power steering system, but it's also hard for me to imagine how it could lock up like that; I would think most malfunctions would result in loss of power steering but not a lock-up.

So I'm thinking it sounds like some mechanical interference, like MasterX suggested.
I once had a '95 Probe GT (Yeah, I know) and the rack started to malfunction.

It would seem to lock up just as I'd come to the exit ramp, or just as I'm entering the decreasing radius part of an exit ramp. Hair raising at highway speed. It would work fine at street speeds, and on the freeway with small steering inputs, but making high speed maneuvers was close to impossible at intermittent times. I found I could apply enough effort to steer the car, (pucker factor off the charts) but it took a lot of effort.

As I remember, it would happen just after a downshift, so the revs were up.

It turned out to be debris in the system clogging some valve that would not allow PSF to flow in either direction at the correct volume. One trip to work, and one trip home with that happening was more than enough for me. My mechanic at the time suspected what was wrong based on a TSB about that model of rack & pinion system. He flushed it out and I never had another issue with it.
I had another thought come to mind, I used to operate a International Military Tractor out on the family ranch, it was bought from a base and the drilling rig cutt off the back where it connected to the PTO and converted to a normal Gannon and Teeth setup for plowing our pastures. It was a diesel and has full hydraulic drive system with 2 speeds on the reduction, it is capable of about 35 MPH, anywho its power steering is very simular to how a car or truck operates, and one time when it ran low on Hydraulic fluid the steering locked up solid, the wheel was literally stuck in place, not even muscling it would move it, and adding fluid fixed it. I wonder if the issue could be similar.

I cannot find the model of our tractor, but it was a custom build for the military with some sort of drilling rig that doubled as a crane originally on the back which was PTO and Hydraulic powered, but it looks nearly identical to this International 660 but ours has extra hardware attached here and there so the 660 was probably the base they added parts to when they made it fit the military's requested capabilities, ours also runs heavy duty truck tires on the front instead of the tractor wheels and tires seen here. The engine looks identical based on its side that is visible, but ours was all dingy camo green flat colored and chipped/worn quite severely.
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