transient shudder in steering

[dcarrb]

This morning, at about 60 MPH, I felt a quick back-and-forth shudder through the steering wheel; just a brief attention-getting shimmy at first but enough to make me pull over to see if I had a tire going down within a half-mile or so. Tires good, I halfway expected to see the power steering pump sucking air, but the level was fine. No loss of boost at low speed, no groaning or change of pitch with load on the pump. I proceeded to work (8 miles or so) @ 50-55 MPH with no repeat performance.

I've noticed a subtle whine for some months that seems isolated around the PS pump and figured a pump might soon be on my shopping list, but I've kept an eye on the fluid level and kept driving. This shudder felt like air in the system, begging the question: Can a bad O-ring allow air into the works without leaking fluid?

Input appreciated, and thanks in advance.

dcb

[TomsSVX]

try hitting some noticable bumps... a bas strut can cause this to happen, best thing to do is find a way for the problem to repeat itself

Tom

[crazyhorse]

With a transient shudder, I'd suspect a wheel out of balance. It's not unheard of for the weights to fall off the wheels. The telltale of a balance problem is that it will fade in & out while holding a steady speed. This will have a definate rythm.

Most other problems will come and go at random. Or at least seemingly at random. With mechanical issues, some input sets up a vibration, that will start fast, but fade out. A blown strut is my prime suspect in this scenario. With no damping, a sharp input will set up a vibration in the spring.

Just my 2bits

[dcarrb]

Well I took the car out at lunchtime and was unable to get it to misbehave again. Drove it kinda hard into a couple of curves then ran it up to about 70 on the highway; rock solid. Decided then to take it to my mechanic for an (long overdue) rotation and balance, left it there and asked him to give everything under the front end a tug while he's got it up on the rack. With the stereo down, in a right-hand curve, I think maybe I heard the left-front wheel bearing growl a bit. We'll see. Thanks again.

dcb

[Trevor]

Originally Posted by dcarrb

I've noticed a subtle whine for some months that seems isolated around the PS pump and figured a pump might soon be on my shopping list, but I've kept an eye on the fluid level and kept driving. This shudder felt like air in the system, begging the question: Can a bad O-ring allow air into the works without leaking fluid?

Input appreciated, and thanks in advance.

dcb

You asked a specific question but appear to have not received a reply.

The whine you report is a one symptom of a leaking O ring. Yes, air can get in without a fluid leak being apparent.

[dcarrb]

Originally Posted by Trevor

The whine you report is a one symptom of a leaking O ring. Yes, air can get in without a fluid leak being apparent.

Interesting. O-ring replacement came up in many of the threads I searched on the topic, but to my mind it seemed the surest sign of a bad O-ring would be a fluid leak.

My mechanic (the shop that has done all the major service on my cars) pronounced everything clean and tight (the fellow who test drove the car remarked about how good the old gal ran out on the highway: "That's a nice car.") I took my usual, very-curvy-backroad route home and felt no hint of shudder. Figure I'll go ahead and change the O-ring.

Thanks again.

dcb

[Trevor]

Originally Posted by dcarrb

Interesting. O-ring replacement came up in many of the threads I searched on the topic, but to my mind it seemed the surest sign of a bad O-ring would be a fluid leak.

My mechanic (the shop that has done all the major service on my cars) pronounced everything clean and tight (the fellow who test drove the car remarked about how good the old gal ran out on the highway: "That's a nice car.") I took my usual, very-curvy-backroad route home and felt no hint of shudder. Figure I'll go ahead and change the O-ring.

Thanks again.

dcb

I had exactly the same thoughts before I replaced the O ring on my car with positive results, as there was no sign of a fluid leak. It must be that fluid does not leak out as the head available at the tank creates only minimill pressure, whereas there can be greater negative air pressure involved, created within the system.