Thud/Pop feeling and sound coming from steering...

JetMechGAC · Post by **JetMechGAC** » 29 Jun 2012, 12:05

Car: 2001 V70 T5 5spd 160k miles with Eibach springs and Koni FSD's.

Description of issue:
-The car has developed a thud/pop feeling/sound.
-It happens when the car is not moving or less than 5mph, engine either running or not, and I turn the steering wheel side to side approximately an inch. Doesn't matter if the wheel is centered, near full lock, or somewhere in between.
-I get a shimmy in the wheel when braking from speed while traveling straight.
-It does not shimmy when braking in a turn or curve.
-I do not have a shimmy when accelerating, crushing, or coasting.
-Maybe or maybe not related, the power steering pump started making a whine/whir sound.

Recent maintenance:
-OEM control arms
-OEM ball joints
-OEM swaybar endlinks
-OEM upper strut mount
-IPD HD upper spring perch
-OEM inner and outer tie rod ends

Troubleshooting:
-I have done all the suspension part replacements. I notice that on my way to the alignment shop that the thud and the shimmy was gone, thinking that the part replacement fixed my issue, only to find that it had returned once everything was back in alignment.
-With the front wheels lifted off the ground there is no issue.
-The brakes (pads/rotors) were replaced by the PO just before I bought it. They have about 15k miles on them. I don't believe the brakes are at fault due to the thud occurring with steering input and there is no shimmy when the front is out of alignment.
-Put a wrench to the steering rack mount bolts/all were tight.
-Power flushed the power steering system with new fluid/didn't fix the pump noise.
-Replaced the pump with one from the JY/didn't fix the pump noise.

I am leaning towards the steering rack but want to be sure before I dive into replacing it. There are no leaks coming from it either.

I have not found any threads related to loose or internally bad racks. All the rack issue threads that I have come across deal with leaking racks.

Anyone have experience with these kind of symptoms? Anything I should look at that I haven't yet?

Post by **jimmy57** » 29 Jun 2012, 12:46

The car is not safe! I'll be there to collect it with a trailer to assure your safety! OK, maybe it is not quite that bad but I am looking for a 5 speed V70 T5 P2 model.

You do not mention any loose motion in the steering that you have noticed. Is there any? I know it was aligned and I assume no alignment error (the equipment can get out of calibration) as you do not mention tires wearing odd or excessively on edges.
I suspect the assist proportioning valve, sometimes known as the spool valve may be the problem. A torsion bar connects the upper splined steering coupling shaft down to the pinion that moves the rack left-right. When the torsion bar yields to the torque needed to move rack it misaligns ports on the proportioning valve to send fluid out of one port to push on the power piston part of rack and opens another port to let the fluid on opposite side of piston to escape out and go back to reservoir via return line. If something gets loose in the valve or torsion bar anchorage then the valve can flutter back and forth. I have replaced racks for this with one having oscillation but most were steering pull with alignment and tires eliminated as causes and effort to move wheel being heavier one direction.
The flow through rack can make the pump noisey. Pumps whine when the pump is powering the wheels right or left, is the noise that same noise?

JetMechGAC · Post by **JetMechGAC** » 01 Jul 2012, 21:50

Not getting rid of the car anytime soon. It took me a solid 5 months to locate this car. Luckily it was only 4 hours away!

It does feel like something is loose. I have had it aligned 3 times in the past year and there has been no unusual tire wear. I should have mentioned that I can replicate the sound/feeling with the engine not running. I'm wondering if there is anything internally to the rack that could fail and cause the symptoms I am experiencing.

Post by **MoVolvos** » 01 Jul 2012, 22:03

JetMechGAC wrote: I should have mentioned that I can replicate the sound/feeling with the engine not running. I'm wondering if there is anything internally to the rack that could fail and cause the symptoms I am experiencing.

Check the Clamps or whatever you call it that holds the Steering Rack. When my brother's 93 850 was new he had a noise that the Dealer could not locate. While changing the oil for him (worked at Pepboy's for half a year) on the rack I just happen to notice it. The Dealer replaced it. Maybe that is the problem?

Blessings,
BKM
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Post by **jimmy57** » 02 Jul 2012, 00:28

The torsion bar is loose or the rack preload guide that holds rack engaged to pinion. If the guide is dry it can make a pop or thud. no ready access to lube it without dismantling the rack.

Post by **MoVolvos** » 02 Jul 2012, 00:40

jimmy57 wrote:
The torsion bar is loose...

Is there some kind of torsion bar on the front end of his car jimmy?

Blessings,
BKM
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Post by **jimmy57** » 02 Jul 2012, 00:59

Described in the first reply I made. It is part of the steering rack.
Have you ever steered a power steering equipped car with engine off and noticed the steering response "rubbery"? the torsion bar in steering shaft into steering gear is the "give" that makes steering have that rubbery feel. I'm talking very slow speed as with driving a car being pushed by hand.
With basic power steering (no electronic variable assist level control) a car with light touch power steering has a weak torsion bar and a car with heavy weighted power steering has a stiffer torsion bar.

Post by **MoVolvos** » 02 Jul 2012, 01:25

jimmy57 wrote:Described in the first reply I made. It is part of the steering rack.
Have you ever steered a power steering equipped car with engine off and noticed the steering response "rubbery"? the torsion bar in steering shaft into steering gear is the "give" that makes steering have that rubbery feel. I'm talking very slow speed as with driving a car being pushed by hand.
With basic power steering (no electronic variable assist level control) a car with light touch power steering has a weak torsion bar and a car with heavy weighted power steering has a stiffer torsion bar.

Got it jimmy thank you!
http://auto.howstuffworks.com/steering4.htm

Blessings,
BKM
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JetMechGAC · Post by **JetMechGAC** » 02 Jul 2012, 08:08

jimmy57 wrote:The torsion bar is loose or the rack preload guide that holds rack engaged to pinion. If the guide is dry it can make a pop or thud. no ready access to lube it without dismantling the rack.

So this is going to be a rack replacement, correct? Anything I should check for in the steering colum?

Post by **jimmy57** » 02 Jul 2012, 08:39

Yes, rack replacement.
The telescoping part of the steering column could wear but I haven't seen that as a problem. On the contrary, the telescoping part gets dry of lube and can give a felt thud on stop and take-off as subframe walks fore-aft and the shaft binds and releases.