ZB Bonnet Stay – Anti Rattle

By Laurie Scott Magnette Enthusiast 01 May 2002

Initially our Z type Magnettes came with a bonnet torsion bar assembly/support. This was replaced with a simpler arrangement, a bonnet stay, for the last of the ZA models and all ZB models. A noticeable problem is the simple bonnet stay loves to rattle and vibrate at idle.
To overcome my annoyance to its persistent agitation the following modification was added to sooth it’s nervous nature.

Bits Required

  1. Heater Hose or similar. O/D = 27mm; I/D = 19mm. [for slotted coupling & retainer]
  2. Heater Hose or similar. O/D = 20mm; I/D = 12.5mm. [for Chamfered Stop]
  3. PVC pipe as used in Australian Telecommunications industry [for slotted coupling]:
    • Designed with one end expanded so pipes can join together [coupled together].
    • 27 mm O/D along its length. Expanded end has 31 mm O/D & 27mm I/D.
    • Manufactured by James Hardie to Telstra reference 73/91
    • Available from Electrical Suppliers
  4. Adhesive. Loctite 406 or similar
  5. Spray paint . Same colour as bonnet stay.

 Basic Idea

Normal setup - The bonnet stay (when stowed) pivots from the front of the bonnet, rearward to rest in a flat clip.

Modified setup – Bonnet stay is undone at its pivot point:

  1. A chamfered stop is pushed onto the bonnet stay, at the pivot end, until it rests against far end, chamfer side facing the pivot end. A slotted coupling is slid onto the bonnet stay. Largest opening first.
  2. A retainer is next pushed onto the stay from the pivot end.
  3. Bonnet stay is now reinstalled with its pivot bolt, spring, washers and nut.

 

Operation –Stow; bonnet stay in the normal way, with the stay cradled in the flat clip and now:

  1. Move slotted coupling rearward so its two slots engage the flat holding clip and rests against the chamfer of the stop.
  2. Slide the rubber retainer against the rear of the slotted coupling
  3. Provided your pivot point is not loose the bonnet stay should be held quietly.
  4. Releasing is the reverse order of above. On days where originality is important all the modified pieces can be quickly removed.

Putting It Together

[1] These are the pieces above. From the left:

-Stop.1.5 cm length of Heater Hose with O/D of 20mm[beveled as shown].

-Coupling Internal. 4.5 cm length of Heater Hose with O/D of 27mm.

-Coupling External. 5.0 cm length of PVC pipe end with O/D of 31mm.

-Retainer. 2.5 cm length of Heater Hose with O/D of 27mm. [11mm punched holes]

 

[2] On the skewer

Top – PVC pipe end. It’s a bend ordered as 73/27120

Lower – Pieces in their order. Note. Internal coupling tube as been glued in.

Putting It Together- Continued

[3] Coupling and Retainer mounted on Bonnet Stay. [Bonnet Propped]

-Coupling and its retainer placed so the parallel guide grooves can be seen.

-PVC has been painted to better blend in.

[4] All the pieces about to come together:

-Bonnet stay on its hook. Note. Not impeded by the chamfered stop [Far right].

-Couplings parallel grooves are about to engage the flat hook.

-Hook [for the bonnet stay], will have its curved part retained inside the coupling.

Putting It Together- Continued

[5] All together

 

Comments

Parallel guide grooves in the coupling can be done with a small angle grinder using a 2.5mm wide disc

Inner part of coupling needs to extend about 5mm so it can contact chamfered stop

If I’m not the only one with a rattle in the stay, then hope this information may be of use

Laurie Scott – MG Car Club [Geelong] Australia