I’ve noticed that quite a few First Gen Dodge Ram Cummins Trucks, even with 100+ thousand miles on them,  still have their engine compartment HVAC insulation cover in relatively good shape.  Mine was still one piece  (but just barely!)  and was badly cracked up and deformed.  It was not worth repairing.

Here's what the OEM insulation cover looked like after 297k miles when removed from the `93 D-250

In order to properly keep the HVAC box cool – since it’s right next to the turbo – I replaced the insulation cover with a custom piece.  I used more of my trusty JC Whitney foil backed insulation!

I had done quite a bit of cutting and forming at this point, but starting with the circular hole for the motor, the remaining effort involved just folding, marking and cutting carefully.

The process here was simple – cut a large flat piece of the material, then start fitting it around the HVAC box.  I first cut out a hole and slot for the blower motor body and rubber boot to protrude through, leaving lots of excess material around the perimeter of the hole to allow for snug fitting of the rest of the insulation.

Here's a photo of the non-foil side while I was forming the main piece. Some foil tape was used on the foil side to hold the shape I wanted.

Then I started shaping the insulation piece by folding, holding, marking, and cutting where needed to conform to the complex shape of the box.  This took a good solid hour or so to complete, because once it was cut off, it is time consuming to add back material (using the tape).  I wanted to avoid cutting off too much at any time.

This shows the front side of the insulation cover as it was coming together, nearly finished actually.

Once the shape was fairly well developed and where I wanted it, the next step was to covert the felt side of the foil backed insulation with foil tape.  This created a double-sided-foil cover.  I also added a layer of tape anywhere that the material was stretched, since the stretched areas tended to crack the foil backed side along the stretch.

The first test fit with final cuts and foil on the inside. The existing bolts for the HVAC were used to secure the cover to the truck.

Close-up view of the top PS side of the cover.

Close up of the top side nearest the heater hoses and the vacuum connections (near the center top of the firewall).

Since the HVAC box bolts were long, I simply poked holes in the insulation cover and then used the existing bolts with additional nuts and washers/fender washers to attach the insulation cover to the truck.

Bottom side, near the firewall drain outlet for the HVAC

The itty-bitty motor cover piece.... I made this so the cover would be completely formed over the HVAC and the electric blower motor. That turbo can get hot! So I needed to fully protect the assembly with double foil backed material.

That turbo can get hot! So I needed to fully protect the assembly with double foil backed material.

This insulation cover has worked out very well – I’ve put more than 1,500 miles towing on the setup, and the cover hasn’t even been phased by the heat from the turbo.

Close-up photo of the finished cover, including motor cover. The Zip Tie is a Click Bond brand cable tie made from high temperature PEEK material.

Nearest the turbo, I did add a layer of foil tape over the foil on the flat surface of insulation, just to have that extra level of protection.

The finished HVAC unit insulation cover.

By the way, when working with the foil backed insulation and tape, your hands can get really grey from the aluminum!

Copyright Kris Wickstead ©2010.  Always use good sense, the proper safety procedures, PPE and safe equipment.  Follow all manufacturers instructions.  For informational purposes only.  Not a guarantee of any kind.  Use information at your own risk.