It has been discussed many times regarding how to insulate the engine bay under the bed. It is time to work on mine.
Some measurements
Under bed: 38*45*1.5
Side:
48*21*1
30*21*1
28*21*1
@Pierce & Gaylie Stewart recommended using Hardie backer and fiber glass insulation material. I don't have the saw to cut them into perfect size. So I need something a little bit easier to install.
I initially want to use thermo-tec (https://www.amazon.com/gp/product/B004PILLZG). According to the spec, it is able to provide direct protection from radiant heat up to 2000F and direct temperature up to 300F. Sounds pretty good. But it is too thin, only 70 mil. That is 0.07 inch. I need many many layers to read 1.5 inch thickness. It is financially not reasonable.
(https://images-na.ssl-images-amazon.com/images/I/81MEfpgx3oL._AC_SL1500_.jpg)
I end up using Dynamat 11905 Hoodliner 32" x 54" x 3/4" (https://www.amazon.com/gp/product/B00069QLVC). It is 3/4 inch thick. much closer to fill the 1.5 inch depth under the bed It has the adhesive on the back. The spec doesn't mention anything regarding the radiant heat or direct heat. Since it is used in engine compartment, I would assume it is safer to be used in diesel engine compartment. There are few reviews mentioned of using it on class A diesel pusher.
The old insulation material are very heavy, I think somebody said there is lead in them. It is high quality material. But expensive. I was thinking installing the new insulation on top of old one. But the old one is too deteriorated to hold any weight. So have to get rid of the old one and clean the surface for the new one.
(https://www.foreforums.com/MGalleryItem.php?id=4494)
Before clean out the old material
(https://www.foreforums.com/MGalleryItem.php?id=4495)
Two different material. I used the hoodliner material.
(https://www.foreforums.com/MGalleryItem.php?id=4496)
It is 0.75 inch thick
(https://www.foreforums.com/MGalleryItem.php?id=4497)
Put a tarp on top of the engine to protect
(https://www.foreforums.com/MGalleryItem.php?id=4498)
Now start the dirty work. Use a putty knife to remove the big chunk then use a wire brush to clean the surface
(https://www.foreforums.com/MGalleryItem.php?id=4499)
Under bed installed
(https://www.foreforums.com/MGalleryItem.php?id=4500)
Reuse old screw and washer. Bought the stainless screw and washer, but they are too big :'(
Avoid using platic washer near the turbo area. Since that is the place with highest temp.
(https://www.foreforums.com/MGalleryItem.php?id=4501)
Start working on side. Wrap all edges using High temperature aluminum foil tape
(https://www.foreforums.com/MGalleryItem.php?id=4502)
Done!
I didn't replace all insulation. Some area are hard to reach. It is not the best work out there, but it is good enough for me. I think the engine noise is muffled a little bit. not much quieter, but doesn't have the high pitched noise.