Holden HQ Sedan

Introduction

After forty six years of service, this vehicle was exhibiting signs of deterioration that were in need of attention. During the consultation, the corrosion issues on the vehicle were assessed and appraised. Each of the defect areas on the vehicle were then broken down further into manageable repairs and presented to the prospective client.

The client was given a detailed explanation of the pros and cons of each of the defect areas. We then prepared a proposal tailored to the clients budget and to rectify the major areas of concern that would impact the structural integrity.

It was determined that the largest risk would come from the cowl area (water ingress into the cabin and including the A-Pillars, floor pans, door hinges and the front windscreen).

Although unknown to us at this stage, this section of the vehicle had been repaired (by others) on two separate occasions. The substandard repairs (presumably cost efficient), had compounded the problem, driving the corrosion deeper into the vehicle structure and inadvertently increasing our scope of work.

Our process involved exploring the route cause of the corrosion issues and restoring the structure by rebuilding it from the inside out.

RHS Front Windscreen Aperture

The photo below illustrates the condition of the right hand side (RHS) of the dash as found, following the removal of the front windscreen.

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Over time the moister that has been trapped by the silicon sealer (and cosmetic repairs), has migrated into the metal structure of the dash panel. The damage was so extensive that it affected the RHS windscreen pillar (aperture), where the stainless steel (S/S) windscreen trim fastens.

The corrosion damage was so advanced that it had penetrated through the upper reaches of the plenum chamber and A-Pillar structure.

Unbeknownst at the time, the corrosion had effected the lower reaches of the plenum chamber also.

RHS Cowl Panel

The photo below illustrates the RHS replacement cowl panel (provided by the owner) being fitted to the vehicle. The panel was aligned with the RHS door and fender, but required a major alteration to fit and align the Stainless Steel windscreen trim.

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Following the removal of the external cowl panel section, it exposed an excessive amount of built-up debris and corrosion species. After the debris was removed, the panel sections beneath were found to be weakened and perforated by the depth of corrosion.

 

This area forms the underlying structure of the cabin with multiple layers of overlapping panels. This section is also the juncture point for the RHS A-Pillar, plenum chamber, dash panel and windscreen cowl panel.

RHS Windscreen Pillar / Door Aperture Section

At first sight this section appeared to be relatively solid, however at closer inspection we’ve identified some hidden issues.

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Apart from the obvious lower section which was missing, the previous repairer has bronze welded a patch (over the top) and filled the void with plastic filler. Originally this section is made up of two layers (the upper & lower sections) to form the structure.

Internal Cowl Panel Duct (plenum chamber)

While removing the Internal Cowl Duct, it was noted that the seal on the underside of the plenum chamber, had corrosion embedded into it. The area where the cowl duct is fixed has been photographed below. This item resides behind the dash and relatively inaccessible to repair.

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The only sure way to fix this issue is to remove the complete external cowl panel to allow access into the plenum chamber.  This was a major unforeseen issue, that if left without repaired would allow water ingress into the vehicle cabin and rusting out the floor pans.

Internal Corrosion Issues

At this stage, the vehicle was far from finished, but still had one more surprise to catch us off guard. Check out the full video of the work completed under the title Rust Repairs-Holden HQ Sedan.

 

Rene Farrace

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