Suspension clunk when braking

[annmax]

Mack Granite 2021, i hear a loud clunk coming from the front suspension when i fully press the brake pedal at a stop or a red light. Nobody can find where it coming from. Any ideas ?

[fjh]

Have someone check the front pins for seizure quite common on the Volvo trash suspension!

[The Heinz]

I second FJH, the pins on the leaf spring fronts don't hold up very well at all, regardless of whether they were greased or not. If you've got drum brakes, you might have some trouble there; we've got one of our church buses doing similar with a loud clunk in the rear when stiff braking. The slacks don't adjust properly, and while I haven't had a chance to check, I'm willing to bet the s-cam bushings are wallowed out too. 

[Mackpro]

In the last few years we have seen that the factory doesn’t grease or tighten any thing very good. As in no grease on the king pins and front steer axle  U-bolts loose. Sometimes the dealership catches it , sometimes not.  I vote spring eye bushings or loose U bolts 

[fjh]

This is why we do pdi inspections and incudes greasing and checking for missing or loose bolts

! Once ran across an mr with a bolt missing on the rh steering arm for the tie rod ! Also a loose steering box missing spacers! Simple oversight’s the could be disastrous for every one involved! Like wheels falling of jets not a great scenario!

[Joey Mack]

I have seen missing u-bolts on steer axles and loose clamps on exhaust, ,  Heck the P.D.I. check list is a few pages long,  

[fjh]

1 hour ago, Joey Mack said:

I have seen missing u-bolts on steer axles and loose clamps on exhaust, ,  Heck the P.D.I. check list is a few pages long,  

Yup!👍

[Nickdieselz]

The loud clunk you're hearing from the front suspension of your 2021 Mack Granite when pressing the brake pedal could be due to several possible causes. Here's a list of things to check that might help pinpoint the issue:

1. Loose or Worn Suspension Components:
   - Control Arms: If the bushings in the control arms are worn out or if the bolts are loose, they could be shifting under the braking force, causing the clunking sound.
   - Ball Joints: Worn ball joints can also cause clunking, especially under load when braking. Check for any play or wear.
   - Sway Bar Links or Bushings: These components help stabilize the suspension and can make a clunking noise if they're worn out or loose.

2. Brake Components:
   - Caliper Bolts: Ensure that the brake calipers are tightly secured. Loose caliper bolts can cause movement when the brakes are applied, resulting in a clunk.
   - Brake Pads: If the brake pads are loose in their mounting brackets, they can shift when braking, causing noise. Check for excessive movement or wear in the pad hardware.
   - Steering Knuckle or Hub Assembly: If there's wear or looseness in the knuckle or hub assembly, it can cause a clunk during braking.

3. Steering Components:
   - Tie Rod Ends: Worn or loose tie rod ends can result in a clunking sound, especially when the vehicle's weight shifts during braking.
   - Steering Gearbox: Ensure the steering gearbox and linkage are securely mounted, as movement in these areas can create noise during braking.

 4. Shock Absorbers or Struts:
   - Worn or damaged shocks/struts can clunk when they compress or extend under the force of braking. Check for oil leaks or signs of damage, and ensure that all mounting bolts are tight.

5. Frame or Body Mounts:
   - Loose or worn body mounts or frame bolts can cause noise as the body shifts relative to the frame under braking forces.

6. Suspension Bump Stops:
   - If the suspension bump stops (which prevent excessive suspension travel) are damaged or missing, the suspension may bottom out under hard braking, causing a clunk.

7. Axle or Driveshaft:
   - Check the front axle or driveshaft for any movement or wear, especially around the U-joints or CV joints, which could contribute to a clunking noise during braking.

Diagnostic Tips:
- Check for Play: With the vehicle on a lift, have someone apply the brakes while you check for play or movement in the suspension or steering components.
- Inspect Under Load: Sometimes, a noise like this only appears under load, so a thorough inspection with the vehicle's weight on the suspension (on ramps or a drive-on lift) may be necessary.
  
By systematically going through these components, you should be able to narrow down the source of the clunk. Let me know if you discover anything specific, and I can provide more guidance from there!