steering chatter about to get me kicked off track

[MFE]

I'm at an audi club DE and the officials are wigged out about steering chatter showing itself as visible shimmy in corners. 92 mustang, new MM k-member, new MM bumpsteer kit, new MM spherical-mount rack bushings on a stock reman rack 3+ yrs old with a stock reman PS pump 2+ yrs old. I have been dealing with steering chatter for years and can't solve it, now due to zero bushing compliance, its shimmying in corners. I have bled the fucking thing til I'm blue in the face. Meanwhile my wife's instructor listened to an old instructor say he wouldn't get in the car, and now he won't get in the car. So she has no instructor, which is what she fucking came here for. I showed the dude (who pointed out, BTW, that our in-car intercom was not, in fact, a Chatterbox as we'd been referring to it as ) that there was nothing at all loose in the system but now I've got to show the car to every "expert" in attendance and deal with every corner worker practically stepping out on the track to eyeball me on every corner. So...any suggestions? The chattering steering predates this rack, this pump, and pretty much evrything on it.

[Carson Lomax]

Didn't Jack say they pinpointed this condition to loading on the rack when aftermarket bushings are used and this is causing the rack to stick? I know you're using the MM spherical bushings that are supposed to prevent that but do you think it's possible the bushings or the way the rack is tightened is having some effect on this? Is it possible to put stock bushings and hardware back on and see if that has an effect?

Just an idea.

[MFE]

I loosened and retightened them, did some system bleeding between sessions, and it was up to its same antics again. And it's dumping fuel out the cap again even though I replaced every fucking thing but the tank last year. The tank is getting pressurized big-time, maybe by exhaust heat, I don't know. Full tailpipes too.

[Tob]

Hubs?

[MFE]

Originally Posted by Tob

Hubs?

nope. But Jack gave me some things to try, namely checking out the valve out of the pump to the high pressure line.
And, we cracked a rotor :lol: at least its not raining.
BTW cc.com loads damn fast on a blackberry

[Bill Richter]

Originally Posted by Tob

Hubs?

X2. I fixed a friend's car (01 GT) at a DE when he had the same complaint. The track officials were going to give him the shoe also. He purchased the car used. I asked him what, if any work had been done to it. On the list of parts recently replaced was the RF hub. Hmmm, lets check that one. A breaker bar yielded a fairly easy 1/4 turn on the hub nut. I torqued it to 250. Mission accomplished. The LF hub nut was ok.

[RichardP]

I recently had a dead ball joint that showed up with similar symptoms to yours.

Good luck finding whatever.


Richard P.

[MFE]

I won't be able to touch the car for days, but I worked up some video to kill time on a flight. In this one, listen to the tires in especially the left handers and you can hear what everyone else was seeing. http://videos.streetfire.net/video/9...a-R_161996.htm

[Jack Hidley]

If the hub was loose enough to cause that noise/vibration, I think the brake pad kickback would make the car undrivable. It's probably a good idea to check the ball joints and inner tie rods.

[Mattie P]

I can hear it. Sounds like the low speed chatter I get on my '92 with a stock k-member and the same bushings.

I can't stand the noise or the feeling through the steering wheel.

[Jack Hidley]

Matt,

Do you mean that you have MMST-7 steering rack bushings on your car? These:

http://www.maximummotorsports.com/st...roducts_id=466

If so, was there steering chatter before you installed the bushings?

[bsharp]

What condition is your steering shaft in? Aftermarket or stock?

[MFE]

Mine's the stock shaft, it's in good shape.

[pj951]

Nice video. I heard some familiar Mustang sound effects.

Whatever the front end is doing you're making it work for you. That '00R wasn't gaining much ground.

[Steve Michael]

I've only been in two mustangs on course and both of them have done that. Mine and a (for now unnamed) 95 Cobra R AI car. I think what I am hearing is a shudder during the tire scrubbing. Is that correct? My car does that on NT-01s and no corner worker has ever approached me. Are they reacting to the sound or the sight of something bouncing, moving in an unAudi way? How is the backlash in your rack? I have a few (uncalibrated arm gage) degrees of back lash in my newer reman'd rack.

The reason I ask if they are just reacting to the sound is...I was once told to pit as if my car was about to burst into flames. When I got to the hot pits, my instructor asked me what that terrible sound was coming from the rear. He thought we were going to die when the rear locked up @ 130. I got to teach this 30 year veteran about mustang brake moan that day.

Oh yeah, both of these mustangs I have been in are MM equipped.

[MFE]

No, they were reacting to visible shimmying. Mostly from an old instructor in an Elise who's probably a very fine driver and instructor and is well respected by the club, but he sounded the alarm after being in close proximity to me on track that I was about to have a wheel fall off "or something", and it snowballed from there in a most surprising an unneccessary way which tested the very limits of what diplomacy I can muster. When I'm parked and I turn the wheel, you can see each front wheel chatter, and I imagine at speed it set up quite a visible cycling. But at least a half a dozen of them got to see for themselves that there is ZERO play in the outer tie rod ends, inner tie rod ends, hubs, or ball joints, and that the rack is bound securely to the K-member.

God help me if he'd heard The Moan LOL.

Infuriatingly, I took the car back out that night on an errand...not a whisper of chatter out of the whole time. Cunt.

[pj951]

Originally Posted by MFE

When I'm parked and I turn the wheel, you can see each front wheel chatter, and I imagine at speed it set up quite a visible cycling.

What is it you're seeing exactly?

[Jack Hidley]

Frazer,

Do you have a power steering cooler installed, other than the 18" long piece of metal tubing that the car comes with? What type of power steering fluid? Do you have any problem with the fluid boiling and over flowing the reservoir? Do you think there is any correlation between the fluid temperature and the steering chatter?

[bsharp]

Are the corner workers seeing the inner or outer wheel during the turns? I ask because I have noticed the inner front wheel move around (wobble) on just about every mustang during fast sweepers that I have been behind. We used to call it dirt tracking because is looked like a sprint car wheel. The outer wheel would not do it.

[Larry]

Originally Posted by MFE

...When I'm parked and I turn the wheel, you can see each front wheel chatter, and I imagine at speed it set up quite a visible cycling...

That seems to clearly be a PS issue and nothing to do with suspension or steering from the inner tie rods outwards. It doesn't do that with the engine off, right? Try turning the wheels with the engine off on dry ground and then on greased trays. Shouldn't make a difference other than the change in effort, right?

I would guess the problem to be a pump pressure regulator, relief valve, or whatever the rack equivalent to a torsion bar/spool valve would be.

It would be interesting to see what a camera under there would find. If the rack itself isn't shaking and there's no slop, then it has to be internal to the PS. A properly damped gage tee'd into the PS high side would also help to pinpoint the cause.

[Dave Dellinger]

I actually had the PS fluid get so hot at Lowe's Motor Speedway in my Tbird that it melted the dipstick in the cap and melted plastic was circulated through the pump. I had to change my line on the track with no power steering.....

But I never had the front chatter. I think spindle flexing was giving me some brake issues, but I am curiously watching this thread.

[Mattie P]

Originally Posted by Jack Hidley

Matt,

Do you mean that you have MMST-7 steering rack bushings on your car? These:

http://www.maximummotorsports.com/st...roducts_id=466

If so, was there steering chatter before you installed the bushings?

Doh!

I guess I don't have the same set up as MFE. I have the MM R&T box on a completely stock '92 coupe. There was no steering chatter before. It only occurs at parking lot speeds I believe. It's been a month since I've driven it. I'm doing a Viper T-56/AOD swap right now and customs and such is a bitch.

[blackbolt9]

If all else fails to work and you can't figure out what the root cause of the issue is could you...

(God forbid)

bandaid it with a steering damper?

I wouldn't suggest this other than the fact you have said all the joints are tight, safe and checked over several times.

[A Grue]

Originally Posted by Jack Hidley

other than the 18" long piece of metal tubing that the car comes with?

Is that the breather tube that runs between the inner tie rod boots?

I think I'm with Larry. If there's no slop in the steering in the paddock, it sounds like either an issue with the rack, or an issue with the pump (or possibly the two acting together).

MFE, how do you sense the chatter from inside the car--does the wheel shake, are you just feeling it through the chassis?

[Jack Hidley]

No, that plastic tube is for air pressure equalization underneath the bellows.

What I'm talking about is the metal tube that is plumbed into the power steering system in the low pressure part of the system. It is in front of the radiator. One line connects to the steering rack return, the other line connects to the reservoir on the power steering pump.

[MFE]

Originally Posted by pj951

What is it you're seeing exactly?

When I'm back home I'll take some video, but as the steering wheel is turned, only when the wheels are on the ground fully loaded and only when the engine is running, the front wheels chatter or ratchet at probably 45 Hz, rather than smoothly and seamlessly turning through their steering travel.

[bsharp]

My car sometimes does that when when I come off the track and everything is very hot. I have seen cars do it when sitting still if the p/s system is not fully bleed, they usually will stop after a while once fluid is added. If they are seeing your inside wheel while you are on the track I think they are seeing normal mustang shenanigans, especially on a car with softer springs.

[MFE]

Originally Posted by Jack Hidley

Frazer,

Do you have a power steering cooler installed, other than the 18" long piece of metal tubing that the car comes with? What type of power steering fluid? Do you have any problem with the fluid boiling and over flowing the reservoir? Do you think there is any correlation between the fluid temperature and the steering chatter?

No auxillary cooler. I'm running synthetic ATF but it's done it to some degree no matter what fluid I've run in it, from Mercon to Type F and now synthetic ATF. I have had problems with fluid coming out the fill cap going back several years to more active autocrossing days, this year I extended the reservoir neck with some industrial hosing and that problem is solved. I'd like to think there's a correlation between fluid temp and the chattering, but I don't believe there is. It's so random. Sometimes it chatters for a while then calms itself down (seems to be when I'm really hauling the mail), sometimes it persists all day long, sometimes it does it first thing in the morning, sometimes not.

Last wednesday at an event at the same track prior to this Audi club deal, we had the car out and my wife drove it first, she came back into grid early and said what the fuck is the matter with this thing? I hopped in with her, checked it out, and said "that's the steering chatter I told you not to be concerned about". I took the car out hot in the very next session and before I had 2 laps complete, the chatter was virtually gone, and stayed that way for the rest of the event, 2 or 3 more sessions for each of us.

But at the Audi event, which was indeed a warmer day, not that it makes a difference, it remained more or less a problem the whole day. Sometimes worse than others, but it was surely there the whole time. Then, like I said, an hour after arriving home I took the car on an errand and the problem was GONE. For the time being.

[MFE]

Originally Posted by A Grue

I think I'm with Larry. If there's no slop in the steering in the paddock, it sounds like either an issue with the rack, or an issue with the pump (or possibly the two acting together).

Jack was gracious enough to offer me a phone number for him while I was at the track, and his thinking is exactly like Larry's, but Jack is leaning toward the valve in the pump. The pisser is, it was chattering before I changed the pump, and before I changed the rack, it just wasn't this bad nor as evident outside the car, that I'm aware of

MFE, how do you sense the chatter from inside the car--does the wheel shake, are you just feeling it through the chassis?

You can feel it in the wheel, and you can hear AND feel the lines banging around. In the worst of cases, you can see it in the wheel. I once zip-tied the lines down to each other and to stable parts nearby an attempt to stop them from audibly banging around when it does this, and the problem got worse. So I freed them back up again and now the mounting is totally factory, right down to the one bracket on the pressure line.

[Damn True]

Just a gut feeling since I know nothing of Mustang steering systems but, I'm thinking you might be foaming your PS fluid either by means of a crappy reservoir, cavitation, or simply boiling it.

If all other components are in good shape I would look at mounting an external cooler and a quality reservoir that will reduce aeration.

[Larry]

Hmm, maybe there is a reason why some cop and taxi cars have a PS cooler.

[MFE]

Originally Posted by Damn True

Just a gut feeling since I know nothing of Mustang steering systems but, I'm thinking you might be foaming your PS fluid either by means of a crappy reservoir, cavitation, or simply boiling it.

If all other components are in good shape I would look at mounting an external cooler and a quality reservoir that will reduce aeration.

Except that sometimes it does it when it's stone cold, and sometimes it doesn't do it when it's been beaten half to death.

[crosser]

Originally Posted by Damn True

Just a gut feeling since I know nothing of Mustang steering systems but, I'm thinking you might be foaming your PS fluid either by means of a crappy reservoir, cavitation, or simply boiling it.

If all other components are in good shape I would look at mounting an external cooler and a quality reservoir that will reduce aeration.

I've been pondering this issue for a while and that same thought crossed my mind. I'm really wondering if you are getting pump cavitation. It definately sounds as if you are getting violent pressure oscillations in the power steering hydraulics, especially if everything else is mechanically sound. Drawing from my expreience with transmission pumps you can get cavitation from a suction limitation/restriction or foaming of the fluid (there are other ways but these are the most common for proven systems). Whats confusing is that you mentioned replacing everything so that would normally rule out a bad pump or a some crap stuck in a suction orifice. Unless there is a bad batch of pumps circulating out there that have the wrong orifice, but this is a WAG.

Fluid foaming is *usually* from the combination of high RPM and high temperature, but not always. The problem with this is that you also mentioned that it's not related to temperature OR RPM......so there goes that.

Is there anywhere there could be a restriction in the lines. A kinked hose, PS cooler with a crimped or damaged tube. Is there some component that has been with the system since the problem started?

[MFE]

Originally Posted by crosser

I've been pondering this issue for a while and that same thought crossed my mind. I'm really wondering if you are getting pump cavitation. It definately sounds as if you are getting violent pressure oscillations in the power steering hydraulics, especially if everything else is mechanically sound. Drawing from my expreience with transmission pumps you can get cavitation from a suction limitation/restriction or foaming of the fluid (there are other ways but these are the most common for proven systems). Whats confusing is that you mentioned replacing everything so that would normally rule out a bad pump or a some crap stuck in a suction orifice. Unless there is a bad batch of pumps circulating out there that have the wrong orifice, but this is a WAG.

Fluid foaming is *usually* from the combination of high RPM and high temperature, but not always. The problem with this is that you also mentioned that it's not related to temperature OR RPM......so there goes that.

Is there anywhere there could be a restriction in the lines. A kinked hose, PS cooler with a crimped or damaged tube. Is there some component that has been with the system since the problem started?

Air in the lines was my primary suspect, theorizing it was compressing the air then moving fluid then recompressing the air then moving fluid and so on, dozens of times per second. And the reason I thought that is I can NOT get this thing bled to the point that I still can't get a little more air out of it. Meaning no matter what I do, I can still observe a bubble coming up through the reservoir after I move the steering lock to lock with the wheels in the air...even after doing exactly that for 15 minutes straight, even when I've rigged up a fitting for a vacuum pump on the reservoir, I'll draw it to 15 lbs vacuum, then cycle the steering back and forth while running the starter with the ingnition disabled, and goddamn if another little bubble won't pop up when I test it again. Even if the car hasn't been run and had a chance to foam the fluid.

Which, by the way, I don't think the fluid is "foaming" per se because I can remove the cap right after shutdown and it's just fluid, not bubbly.

The lines are all in good shape and only a couple years old, and routed just like factory so no kinks. I replaced them when I replaced the pump a couple years ago.

[MFE]

BTW it's got an underdrive crank pulley on it so I don't think I'm overspeeding the pump, I only ever run the car up to about 5800 RPM.

I've never seen inside one of these pumps, jack was explaining they're a very simple stator setup, but I wonder, if the stator or turbine was damaged, say missing a piece of a fin or something, might it not cause the output pressure to drop every rotation, perhaps causing this?

[Tobey]

I'm not a mechanical engineer, and this may be a stupid suggestion, but could there be a hair-line crack in the pump/line/connector/etc. on the suction side that under certain conditions lets air get sucked in, but doesn't let a noticeable amount of fluid leak out when it's sitting still?

[Larry]

That's not that uncommon. However, unless there was a restriction (like a kink or the inside layer of the suction hose delaminating), it may not be likely to get to the point where it could suck air.

A brake hose can delaminate internally, allowing the buildup of pressure without allowing the fluid (and built up pressure) to return, so it's possible that could happen to PS hoses, either on the pressure side or starving/sucking air/cavitating on the return side - which could also include fittings/O-rings I suppose.

So, we've allegedly by-process-of-elimination'ed the following:

suspension parts
steering linkage
steering shaft/joint
rack
pump
too little fluid
too hot fluid
wrong fluid

It doesn't chatter when the engine's off (I'm assuming that). A KOEO (key on engine off) coast down a grade where you can crank the wheel to do some sweeper turns would verify this and I'll bet there would be no chatter.

I learned a long time ago that new or rebuilt does not necessarily = Good. With that, my cynical mind finds the only thing left is the PS system itself (in order of likelihood IMO):

1) defective/incorrect replacement pump
2) defective/incorrect replacement rack
3) PS hose issue as described above

Did I miss anything?

Oh btw, I'd be wary of rebuilt r&p racks. Apparently the rebuild industry does a good job of cleaning and painting and replacing seals but not regrinding and hardchroming the rack/metal bushing interface. At least one of the aftermarket alignment parts companies (might have been Northstar???) specifically recommends against ever installing a rebuilt r&p rack because of this to reduce customer complaints.

[Niles]

Originally Posted by Larry

Oh btw, I'd be wary of rebuilt r&p racks. Apparently the rebuild industry does a good job of cleaning and painting and replacing seals but not regrinding and hardchroming the rack/metal bushing interface.

This is something everyone should know about every rebuilt part. Most parts (pumps, gears, cv joints, etc) are machined one size over, often removing the thin surface hardened layer (nitriding, chroming, polishing, whatever) resulting in reduced life and performance. You absolutely get what you pay for.

[A Grue]

Then how do you get a decent part for things that aren't really available brand new? Even the racks from Ford are remans, anything new from AGR or FR costs a small fortune.

MFE, you said you're using the stock steering shaft, in good shape. Is it original to the car, or a newer OEM replacement? I've heard bad things about the Fox rag joint...

[Tom Beverly]

Dumb question, but is the spring/piston assembly still installed in the pressure hose fitting (where the high pressure hose screws into the side of the pump)?