1984 300SD engine compartment hood insulation

The old black foam insulation stuck to the underside of the hood turned to dust with a finger poke, and some of it was missing. A friend mentioned that without the insulation, the heat from the engine would cause the paint to quickly fail on that spot of the hood.

I went to Lowes and got a roll of aluminiumized Mylar bubble sandwich insulation. I needed a 3-foot wide roll to do it in one piece, so naturally I had to buy the 4' x 25' roll for $43. I rationalized it by saying, that's enough to do it 4 times to get it right, and it costs about the same as the replacement insulation from the auto parts store.



The hood came off the car pretty easy with a helper. I unplugged the wires to the squirter heaters, and the feed tube for the squirters. The clips and pins came out of the hood hinges easy. Be careful not to drop the back edge of the hood onto the windshield as you remove it. There is a trick when reinstalling the hood pins. Two of them have a bump under the head of the pin that fits into a detent in the pin socket. Turn the pin so those line up or you won't fully seat the pin or get the retaining clip on it.

I put the hood shinny side down on a folding table with blankets for padding.

I used a plastic scraper to remove most of the old foam. It came off easy and smelled strongly of diesel saturation. The big pieces when straight into a nearby trashcan. The 5 gallon shopvac came in handy to suck up the smaller bits and dust and avoid a mess.

I used a 3-inch razor scraper to clean most of the old glue and remaining pad off the metal.

I rolled out the bubble insulation and cut it large. I slowly and carefully trimmed it to the shape of the front of the hood so that it would tuck under the lip. As I worked my way around, trimming it bit by bit I kept tucking it under the lip. This kept it from sliding around so it was easy to make accurate cuts.



When I got on the down-sun side of the hood, it was way too bright with the sun in my eyes, reflecting off the insulation, so I rotated the hood to be working on the up-sun side again.

After the piece was fully trimmed and tucked into the lip, I carefully untucked the front half of the insulation and folded it up 90 degrees. I sprayed 3M contact cement in the middle area of the hood and up on the insulation, avoiding getting it too close to the edges. I waited about 10 seconds for the cement to start getting tacky and carefully lowered the insulation onto the hood trying to avoid wrinkles, and tucked the edges back under the lip. I took a break for about 10 minutes to let the glue set.

Then I untucked the back half of the insulation and repeated the glue process.



I'm fairly pleased with how this project turned out. There are some small wrinkles, but nothing serious. What I like best about this type of insulation is that when a fuel line pops off, it won't get saturated with diesel, like the foam does.

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1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI