Knocking in suspension

General Discussion
1

I have a 2004 Santa Fe.

There has been a consistent knocking in the driver-side front of my car for the past 5 or so months. I can’t tell if it’s getting worse or not. It isn’t there at low speeds, but is obvious at high speeds, and it goes away when I turn. It almost sounds like there is a loose wheel, but there is not.

I replaced the steering knuckle in the driver’s side 2 or 3 months ago so it’s not the bearing (a new bearing was part of the knuckle assembly). When doing so I looked at the CV axel which appeared to be fine. My thought at this point is an unbalanced tire, or maybe a warped rotor, or maybe something with the pads? I changed the rear brakes not long ago, but not the fronts, and when I brake, at low speeds, I can kind of feel the pads catching and releasing in the brake pedal.

2

Most likely your stabilizer bar link if it is a single knock. Replace both, they are cheap.

Also possible is the upper strut mount. If the noise sounds like a loose pile of lumber on rough roads, a bad strut mount is likely.

Also but less likely, is a bad strut if it has been visibly leaking.

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3

unfortunately, it’s not just a single knock, but it’s a continuous and rhythmic knocking - should have said that in the original post. I was considering just replacing all my suspension components at some point soon. Can get the whole kit for around 200.

4

If you are only paying 200 for a “whole suspension” I’d strongly recommend not. Too cheap, low quality junk. The whole suspension consists of too many parts to only be $200. Either parts are junk or the kit doesn’t have all the parts. I’d be concerned about $200 quick struts being junk.

As I posted, the noise you describe is likely bad strut mounts.

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5

Much appreciated.

The whole suspension probably wasn’t the best way to describe it. I’m talking sway bars, stabilizers, tie rod ends, and control arms. I compared it to things that rock auto carries and it seems ok. I appreciate your input!

6

Agree but just looking at a cv joint doesn’t mean it’s not worn out. A mechanic should be able to isolate the problem by listening to the noise.

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7

First guess - CV joint(s)

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8

That doesn’t include strut assemblies does it?

9

just so you know…

Front Coil Spring Corrosion
If the front coil spring fractures due to corrosion it could cause the coil spring to make contact with the tire, possibly puncturing the tire and increasing the risk of a vehicle crash.

NHTSA Campaign Number: 14V435000

Manufacturer Hyundai Motor Company

Components SUSPENSION

Potential Number of Units Affected 271,773

Summary

Hyundai Motor Company (Hyundai) is recalling certain model Year 2001-2006 Santa Fe vehicles manufactured from March 31, 2000, through February 15, 2006, that are registered and operated, or which were originally sold and registered, in the following 20 “salt belt" states and the District of Columbia: Connecticut, Delaware, Illinois, Indiana, Iowa, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Vermont, West Virginia, and Wisconsin. The affected vehicles may experience front coil spring corrosion from road salt, causing the coil spring to fracture and make contact with the tire.

Remedy

Hyundai will notify owners, and dealers will inspect and if necessary replace the coil spring, free of charge. The recall began on October 24, 2014. Owners may contact Hyundai customer service at 1-800-633-5151. Hyundai’s number for this recall is 124.

Notes

Owners may also contact the National Highway Traffic Safety Administration Vehicle Safety Hotline at 1-888-327-4236 (TTY 1-800-424-9153), or go to www.safercar.gov.

6 Affected Products

Vehicle

MAKE MODEL YEAR
HYUNDAI SANTA FE 2001-2006

27 Associated Documents

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10

No, no strut assemblies in those.

11

Checked the CV Axle when I changed the knuckle and was fine. Knocking pre-dates the knuckle.

12

A worn CV joint can have no outward sign of wear.

It certainly could be something else, I’d go with @Mustangman 's strut suggestion, check it out. I would not throw a whole new set of parts at it until I found the source of the knocking.

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13

A CV joint noise would probably sound different as the wheel speed increases. Maybe you can find a place that safe to do an experiment, get up to a speed you hear the noise, then let off the gas pedal and listen to how the sound changes as you slow down. If the frequency of the knocking follows the wheel speed, could be a faulty CV axle. Note that either of the two CV joints at each the end of axle could be faulty.

My opinion, this isn’t a CV axle problem. More likely some sort of suspension system problem, and the test above will not show a strong correlation to wheel speed and the sound made. If it is a CV axle problem, most likely the inner CV joint. Outer CV joints tend to make noises more when turning, and usually noticed more at lower speeds.

14

Curiously, I have done this experiment. No change in the pace of the knocking in correlation to the speed. Once it starts it’s consistent throughout the ride until I brake (below 10-15 mph), and sometimes it goes away as the ride gets longer. Also, I realized on my way home from work that it doesn’t do it every ride either (this and the thing where it goes away after a while is why I was thinking an unbalanced tire?). Like I said too, there’s absolutely no vibration in the wheel or pedals or car. It’s literally just a rhythmic knock (I was thinking motor mounts at one point, but that seemed unlikely to me).

15

Any difference with changes to the road surface?

16

To me, this points to a shock absorber bushing. The reason is that in the early days of automobiles, engineers knew that they cold never get a car to ride perfectly smooth, but if the car oscillates at 100 times a minute, passengers inside would not feel it.

Below that rate, it feels choppy, above that rate makes passengers “sea sick” (motion sickness). That might be because our normal walking cadence is 100 steps per minute and walking makes your head go up and down with each step.

When a shock bushing gets worn out, then it will knock twice for every oscillation, and it will not vary with speed. Could be a sway bar link also as suggested by @Mustangman.

17

I’m just sayin is all, you don’t always get the normal symptoms. I had a cv go bad on the way to work at freeway speeds. No noise but just noticed a slight vibration. I pulled into my stall and when I backed up all of the ball bearings fell out. Strut noise or upper mount noise will be clearly different than a drive train noise.

18

Backwards… 100 cycles per minute is 1.67 cycles per second (or hz).

Most luxury cars have damped natural ride frequencies in the 1.2 hz range because it provides a very soft ride. Sporty cars in the 1.5-2.0 range. Most others in-between. My Mustang is 1.5 front and 1.6 rear. My Camaro race car up in the 1.9 range … it very stiff dampers lowering the frequency but it was very stiff.

Below 1.1 hz or so (66 cycles per minute) it can make passengers queasy… into the 5-7 hz range you are flirting with what we used to call the barf frequency. 5-7 hz is the natural frequency of your internal organs. Engine bounce is usually set to about 9 hz for that reason. The tire-wheel-brake natural frequency is 11 to 18 hz with the low profile tires being up towards 18 and the soft squishy tires being around 11-12 hz. The tire motion against the bushing gives you the “loose lumber” noises I mentioned in my first post in this thread.

Roll natural frequencies hover around 3.5-4.5 hz or so. Yaw (rotation) is in a similar range but varies quite a bit depending on powertrain location. Mid-engine is FAST (5 hz), front engine, rear transaxle is slow but with short wheelbase (Corvette, Porsche 944) is faster. Long FWD cars are fairly low 3 hz

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19

Jack the car up, take the wheel off, and do a thorough job of inspecting the suspension components. Generally that’s all it takes to pinpoint a suspension problem.

Match the frequency of the noise to speed of the component.

20

If you don’t mind I’ll print this out. The wife suffers from motion sickness unless she drives.

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