500 Sound Insulation - Rear Section

Introduction

Good as the 500 is in many ways, it lacks a basic coating of sound insulation (that benefits the higher specification Pandas) and so is extremely noisy particularly in diesel form.

Presumably Fiat have done without it to save weight for better emissions, to maximise head room in the rear and perhaps for cost reasons. With the diesel having exactly 110g/km CO2 emissions, clearly weight was critical.

What Can Be Improved

There are four main areas to improve:

• The doors, which will be covered in a seperate article, which reduces transmission of noise from other vehicles and improves the sound systems bass output (where a sub-woofer is not fitted);
• The floor pan and fire wall, which will also be covered in a seperate article, which reduces road noise from the front wheels, engine noise and exhaust noise;
• The roof, which I have not considered since headlining is difficult to remove and very easily damaged, and in any case wind noise is barely audible due to the levels of other noise sources; and
• The rear section of the car - the subject of this article - including the rear quarters, boot, and under the rear seats.

Tools Required

• 1/2" drive socket set
• Allen keys
• Sharp scissors

A panel removing tool will also assist, but is not absolutely necessary.

Materials Required

• 12mm felt underlay - around 5-7 sq.m
• A few spare Fiat panel clips of each type (grey and blue/green)
• Optionally, non-bitumen based self adhesive sound insulation materials such as Dynamat or Damplifier
• Selection of plasters to cover various nuckle skinnings

Materials such as Dynamat are applied to sheet metals to reduce viabration in the panels. Also thin, they are effective in reducing transmission of low frequency sounds (mostly below around 200Hz). Thicker layers of dense, soft materials are required to absorb higher frequency sounds that make up the majority of road noise. A combination will provide the best reduction.

Bitumen based self adhesive pads or not recommended since they degrade and can become detached or melted at temperatures attainable within a car sitting in hot sun. They also have an odour, particularly when warm.

Method

Removal of Boot Trimmings

• The parcel shelf simply pulls out.
• The boot lining simply pulls up and out.
• The trim around the boot catch is secured by two screws and then can be pulled upwards sharply to overcome several plastic clips. This is good practice for later! The panel will not break, and the clips can be replaced in the unlikely even that they break or spring off somewhere and get lost.
  
• Side panel carpetting is secured with a single plastic rivot, which can be pulled out or released using a trim removal tool.
• The boot lid carpetting is secured with numerous plastic rivots, which can be removed as above, and four spring clips. Once the plastic rivots are removed, the carpet panel can be eased towards the glass to release the clips.
  

Removal of Rear Seats

• The seat base panel is secured only by two bolts visible from within the car.
• Once the bolts are removed, the seat pulls forwards and upwards. There is very little play on the seat belt clips recessed into the centre of the seat and care is required to work them out without damaging the fabrics or leather.
• The split rear seats are secured by two bolts each side and a steel securing strip covering the centre pivot. This strip can be removed by removing the single allen bolt and sliding it out towards the front of the car with the seats down, taking care not to damage the seat farbrics or leather.
• The pair of seats can then be lifted out of the hasp and twisted a little to enable the two seats to be seperated (simply pull apart). Once seperated they can be safely removed from the car.
• Once the seats are removed, the rear seatbelt lower mountings can be unbolted.

Removal of Plastic Trim Panels

• The rear parcel shelf support trim is held in place with one screw under it and another screw through the rear quarter panel. Once removed the panel can be pulled away, overcoming the plastic clips.
• The rear pillar trim from which the seatbelt protrudes is held only with clips and simply pulls off:
  
• The trim panel with the front seatbelt upper mountings must be removed. The plastic cap covering the bolt simply pops off and then the seatbelt bolt can be removed. The lower section then pops outwards and the panel is then released by sliding downwards. Despite the "Airbag" engraving, there is no air bag behind this panel (presumably they are within the headlining). Be careful not to loose the plastic clips into the bodywork!
• The plastic strips along the doors must next be released. Full removal is not necessary. Release the two screws at the end nearest the rear quarter panel and pull sharply upwards, working along to about half way, to release the plastic clips.
• The rear quarter panels can now be removed. There are a few screws at the corners, and panel clips:
  
• Work slowly and don't force the panels. The bottom needs to be worked up around the rear seat bar, unless this is removed, and then the panel popped off. It might be easiest to start at the point that the front seatbelt goes through the panel, since a small piece of trim unclips and allows access to the clips behind it.
• Note that the panel cannot be fully removed since the front seat belt lower mounting point is through it and includes the pre-tensioner mechanism, which should not be disturbed.

Installation of Insulation Sheets

General Considerations:

• If adding self adhesive panels, the rear wheel arches and inside the rear quarter panel should be covered. The inside of the rear quarter panel, around the speaker, may also be worthwhile.
• Cutting felt panels will make a lot of fluff and dust. Cut them approximately to size outside the car and then trim to fit.

Wheel arches and Quarter Panels:

• Cover the wheel arches, tucking under the cables to hold in place. Cut around cable clips as there is not much clearance and use a maximum thickness of about 12mm.
• Do not cover the electrical units concealed in the rear quarters. On the passenger side is the Blue&Me unit, and on the drivers side is the Interscope Amplifier (if fitted). Bear in mind that the Interscope amp in particular will generate a fair bit of heat when worked hard.
• Do not remove the factory fitted layer applied to the inside of the wheel arches
• Cut pieces large enough to be curled around at the bottom over the factory insulation, run up the outer skin, and curled around at the top to hold in place.
• As access is restricted, an seperate piece may be required to cover the metalwork towards the front of the car, behind the speaker.
• Insulation can also be added in the recess that the front seat belt mechanism is mounted, but be sure that it's tucked behind so to avoid rubbing on the belt and clogging it up.
• A completed installation:
• Once the rear quarter panels have been replaced, two large pieces can then be cut to cover the entire boot floor, tucking under the seat mounting bar, and under the rear seat, tucking into the carpet down to about where the seat mounting bolts and again under the seat mounting bar.

Boot Lid

• The boot lid is also bare from the factory:
• There is sufficient clearance to add an 8-12mm layer.
• Use wire clippers to chop holes for the plastic rivots.
• Cover only the flat area, don't wrap it under the bottom as the carpet will not then fit over the lock.
• Completed installation:

Reassembly

• Reassembly is broadly the reverse of the above.
• Any plastic mounts can be replaced - they simply side into the panels.
• Ensure all bolts are replaced, and firmly tightened. Work them in by hand until they are well in to avoid the possibility of damaging the threads.
• The rear quarter panels may not push fully home in places due to the thickness of the insulation. This doesn't matter as they'll be firmly held by the seats anyway.
• The boot side panel carpets are a little fiddly to replace due to the thickness under them.

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