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Discussion Starter #1
I recently noticed that my power steering in my Mustang has a slight jiggle or shudder near full lock at low speeds. It will also do it sometimes when it’s loaded heavily, like taking a corner at speed, and it can be anywhere during the rotation of the steering wheel then. I have a Taurus rack and pinion and a PS pump from a later model Ford (90’s vintage if I remember correctly). Fluid level is good, as is color and smell of ps fluid (Dextron III in this case). I do have the smallest of leaks (more like seepage as it hasn’t dripped but it’s wet) on the PS return hose where it attaches to the rack. I’ve never had a PS pump go bad this way, but is the pump on its way out? I’ve dealt with very noisy pumps, and pumps with bad seals, air in the system, etc, but have never felt this jiggle with an otherwise non leaky and quiet hydraulic system. The rack feels tight, and the fact that it will do it anywhere in the steering wheel rotation is pointing me to the pump. Could the fluid have broken down and need to be flushed? But if the fluid was spent wouldn’t the pump be noisy?

Your input is appreciated!
 

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I have experienced when mixing up parts, Non stock, ill fitting pieces to build, many facts are involved. Yes, it gets perplexing, confusing.
Question? Why did you not use stock components? Folks here MIGHT be able to help if a stock, correct system was installed.
 

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I recently noticed that my power steering in my Mustang has a slight jiggle or shudder near full lock at low speeds. It will also do it sometimes when it’s loaded heavily, like taking a corner at speed, and it can be anywhere during the rotation of the steering wheel then. I have a Taurus rack and pinion and a PS pump from a later model Ford (90’s vintage if I remember correctly). Fluid level is good, as is color and smell of ps fluid (Dextron III in this case). I do have the smallest of leaks (more like seepage as it hasn’t dripped but it’s wet) on the PS return hose where it attaches to the rack. I’ve never had a PS pump go bad this way, but is the pump on its way out? I’ve dealt with very noisy pumps, and pumps with bad seals, air in the system, etc, but have never felt this jiggle with an otherwise non leaky and quiet hydraulic system. The rack feels tight, and the fact that it will do it anywhere in the steering wheel rotation is pointing me to the pump. Could the fluid have broken down and need to be flushed? But if the fluid was spent wouldn’t the pump be noisy?

Your input is appreciated!
My comments assume the rack is hard fastened to the car and not bracketed in rubber. (you can get funky behavior with that)

Really wondering if air isn't in that system. Your statement - "smallest of leaks on the PS return where it attaches to the rack" -
makes me suspicious of this. How could this situation exist and air NOT be in the system?
After exhausting this possibility, my next stop would be the pump itself......

ex-Global West GM
1991-1995
 

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Discussion Starter #4
My comments assume the rack is hard fastened to the car and not bracketed in rubber. (you can get funky behavior with that)

Really wondering if air isn't in that system. Your statement - "smallest of leaks on the PS return where it attaches to the rack" -
makes me suspicious of this. How could this situation exist and air NOT be in the system?
After exhausting this possibility, my next stop would be the pump itself......

ex-Global West GM
1991-1995
Rack is solid mounted, yes. I was leaning toward that return hose being the first step as well, but I didn’t know if a failing PS pump exhibited certain symptoms similar to what I am seeing.

I recently struggled with our Subaru PS system after changing out a leaky pump. Once you disturb that system the air leaks cause horrendous noise with no visible fluid leaks. Makes it a giant PITA to find the problem spot so you end up changing parts one after the next until you fix the problem part. Stupid.

And I’ve had this steering system installed for darn near 80,000 miles and this is the first time it’s had trouble. The original PS system was awful in comparison!
 

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Rack is solid mounted, yes. I was leaning toward that return hose being the first step as well, but I didn’t know if a failing PS pump exhibited certain symptoms similar to what I am seeing.

I recently struggled with our Subaru PS system after changing out a leaky pump. Once you disturb that system the air leaks cause horrendous noise with no visible fluid leaks. Makes it a giant PITA to find the problem spot so you end up changing parts one after the next until you fix the problem part. Stupid.

And I’ve had this steering system installed for darn near 80,000 miles and this is the first time it’s had trouble. The original PS system was awful in comparison!
Failing pump generally is just high effort at the wheel..... unless the internals are shedding and bits and pieces are migrating.
Then you have other issues.
If the rack had been mounted in rubber and the pump going out, you could have interesting harmonics....

Worked on a few Subaru's but not steering. They have flow charts at the dealer level that help out and the
independent repair shops have some online blogs & networks they subscribe to but for the DIYer it's
generally hunt & peck on a lot of Subie stuff, even with a shop manual.

Original Bendix steering is great when "tuned," I never found it worth a crap stock. The pump pulleys tend to be too small,
the rubber ram bushings are a joke, the reaction valve springs in the control valve are better suited for a luxo-barge
than a Mustang, the Thompson/Ford pump has some design shortcomings, etc.
It can be tweaked to work fine though. I road raced with that system.
You frequently hear that the Corvette had the same system (and vette owners aren't complaining) but although similar
in design and the basic patent is the same, there are some definite differences between Corvette steering internals and
Mustang. The early Nova wears a similar Bendix system and it's different as well.
I've worked on all of them.....

ex-Global West GM
1991-1995
 

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Discussion Starter #6
So I replaced the leaky return hose, filled it back up, and fired it up... shimmy/shake in the steering wheel is still there. :( I guess the next thing to replace is the pump. The pump is acting like the overpressure relief (internal to the pump) is popping off too soon and causing a weird chatter which is felt in the steering wheel.

I’ll order a new pump and swap it out next weekend, then hopefully that will fix it.
 

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Leaky/wet return line can definitely introduce air into the system, as it is low pressure (suction) relative to the high pressure supply line..

Having now replaced it, (and introduced more air) have you gone thru the procedure to bleed air from the system?

That is, with wheels in the air, engine running, cap off pump, cycle steering slowly thru full left/right (lock to lock)about 20 times

Sent from my SM-G950F using Tapatalk
 

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Discussion Starter #8
I got my new pump installed the other night and all is well again. Before I swapped it out I had a coworker crank the steering wheel a few times while I listened in the engine bay and the old pump made quite a bit of whining and moaning, I just couldn't hear it from the drivers seat over the engine and exhaust noise. :)

All fixed!
 

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Discussion Starter #9
A quick update.... the new power steering pump wasn’t the only problem. I discovered that the rack and pinion has an adjustment for meshing the rack to the pinion. A few days after the pump change I still felt the slightest bit of shudder at a specific spot while turning the steering wheel. That’s when, after a bit of googling, I found out about adjusting the gearing preload In the rack. After adjusting the preload on the rack it restored the tight feel and the shudder is completely gone now!

If you have a car with rack and pinion steering with a few miles on it, I’d suggest taking a look at this adjustment. It feels like a brand new rack now; tight, no slop, and very precise feel. This is basically what I did...
 
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