Mazda 3 BK/BL - Front suspension knocking or clunking

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This bulletin, provided by KYB Shock Absorbers, will explain the knocking or clunking noise common to the Mazda 3 BK/BL Series’ front suspension.

The Mazda 3 BK/BL series were manufactured and delivered from 01/2004 to 01/2014 and were very popular with Australian customers, as there are still over 300,000 of these vehicles on Australian roads with this issue increasing.

Some of the comments we've received from customers include:

“My car has developed an irritating knocking sound from the front.”

“I just replaced my shock absorbers because of a clunking sound, but it’s still there.”

“After replacing my front struts three times with different brands, I still have knocking sound from the front. Please help.”

The front suspension of the Mazda 3 BK/BL series incorporated a Macpherson strut that acts as both a shock damper and steering pivot.

The strut is designed with brackets that retain the ABS & brakes lines and a stabiliser link rod. To form part of the suspension assembly, the strut is joined to the steering knuckle assembly via a unique ‘C Clamp’ mount (See Image).

Front Suspension Assembly – Examination & Recommendation:

Based on the feedback from our customers, a thorough investigation was undertaken by KYB engineers, which involved multiple on-vehicle road tests and in-depth product assessments.

After all the tests were completed, the most common causes of the front suspension ‘knocking/clunking’ noise was diagnosed to include one or a combination of the below:

1. Loose or worn strut mount & bearing – Allows the strut assembly to shift both vertically & horizontally
   • Check tightening torque of the piston rod nut (56.9 - 76.4 Nm), and shock absorber upper bolts (19.1 - 27.9 Nm)
   • Inspect the strut mount & bearing for visual damage and replace if required

2. Loose or worn stabiliser control link – Allows the link to shift in position
   • Check tightening torque of the stabiliser control link upper nut (42.3 - 60.1 Nm)
   • Inspect the stabiliser control link for visual damage and replace if required

3. Loose or worn tie-rod end ball joint – Allows the joint to shift in position
   • Check tightening torque of the tie-rod end ball joint nut (37.2 - 50.4 Nm)
   • Inspect the tie-rod end ball joint for visual damage and replace if required

4. Split/broken or incorrect bump stop – Allows the bump stop to rattle and bounce
   • Replace bump stop

5. Split/broken or incorrect dust boot – Allows the dust boot to rattle and bounce
   • Replace dust boot

6. Loose ‘C-Clamp’ mounting bracket – Allows the strut to spin or lift within the C-Clamp
   • Check tightening torque of the shock absorber lower bolt (53.9 - 73.5 Nm)
   • Inspect the shock absorber for visual damage – Scratch marks/missing paint

Front Suspension Assembly – Removal/Installation Process:

To assist with the diagnosis of the front suspension ‘knocking/clunking’ noise, listed below is a step by step removal & installation process for the Mazda 3 BK/BL series:

1. Remove suspension components in the order indicated in the above image
2. Install in the reverse order of removal – apply correct Mazda tightening torque (Nm)
3. Inspect and adjust front wheel alignment as necessary

Please Note: It is always recommended to road test a car before and after suspension work is completed, to confirm the noise has been eliminated.

IMPORTANT NOTES:

• It is common that the front strut mount may adjust position during the final road test. It is advised to recheck both top piston rod nuts – to confirm correct tightening torque (56.9 - 76.4 Nm)