M939 Series Hood Insulation

[Cruceno]

Has anyone been able to locate a suitable replacement for the insulation batting under the hood of the 939 series?

I've searched till I ran out of internet, and found several people that were missing or planning on replacing their insulation, but have not found anyone who has actually done it.

I'm completely missing the panel that goes across the hood of my 923, and the two sides are in desparate need of replacement. Just wanted to see if anyone else had used a particular product, or found the genuine article for sale before I venture out on my own to find some.

 

[1 Patriot-of-many]

Have you tried all the usual places like Eriks and TNJMurray? CALL them.

 

[Cruceno]

Yep, I always check those places first. Erik's has under hood insulation for the M35A3, but not for the 900 series.

 

[FASTNOVA]

I'll be in search of one too.

 

[aheilmann68]

I too have this issue. I found mcmaster carr has sound dampening foam that I was thinking of getting. Go to raw material, foam, sound insulating for the choices.

 

[swbradley1]

Okay, I'll bite, what is a 900 series?

 

[zguinness]

Gonna keep an eye on this one. I'm missing the large section of insulation under the hood as well.

Okay, I'll bite, what is a 900 series?

I think he's referring to M939 series trucks

 

[M35A2-AZ]

I was thinking of using the sound and heat sheets that they use on cars for the floor board and fire walls.
I think you pill the back off and it sticks to the surface.

 

[Trailboss]

I don't know if I want to replace the OEM foam with the same stuff. It seems too often to degrade and fall off in chunks which turn to powder when you try to pick them up. There has got to be a better product out there. But, then maybe this is the only stuff available that when it falls off it doesn't damage the belts or fan, or melt or ignite on the manifold.

 

[juanprado]

There are parts of it on ebay. Get the nsn numbers from the parts tm and google ebay as I can't post a link

It takes 4 different pieces to do a complete hood. Another potential source is the trucks getting parted.

 

[zguinness]

I saw the smaller side pieces on ebay but they don't have the large center piece (mine came with that section missing).

 

[Cruceno]

I too have this issue. I found mcmaster carr has sound dampening foam that I was thinking of getting. Go to raw material, foam, sound insulating for the choices.

I was actually just looking at some deadening foam at Grainger last night. I was a little concerned that the temperature ranges it could be used with were a little low (it maxed out in the low 200 degrees if I remember). I don't want that stuff melting down onto my engine! I'll check McMaster out tonight to see what they have.

Okay, I'll bite, what is a 900 series?

I think he's referring to M939 series trucks

Sorry about the confusion fellas. I posted late last night/early this morning. Clearly wasn't firing on all cylinders! I definitely meant the M939 series trucks. Thanks zguinness.

I don't know if I want to replace the OEM foam with the same stuff. It seems too often to degrade and fall off in chunks which turn to powder when you try to pick them up. There has got to be a better product out there.

Im leaning this way myself. The OEM stuff I do have is dry rotted and turns to dust with the slightest touch. Whatever I end up getting, I want it all to match. I don't want to have OEM side panels, but Dynamat (or other product) across the hood.

There are parts of it on ebay. Get the nsn numbers from the parts tm and google ebay as I can't post a link

It takes 4 different pieces to do a complete hood. Another potential source is the trucks getting parted.

.

Thanks Juan, you're absolutely correct, there are 4 pieces that make up the insulation kit. I always forget about the small forwardmost section. I'm missing that one too. I've been steadily looking on eBay by searching NSN's and a variety of keywords, but haven't found either of the pieces that go across the hood.



Thanks for the replies Gents. I guess I'll keep looking, see what I can find, and post the results back here. If anyone has any additional advice/leads/suggestions feel free to post up.

 

[juanprado]

Mine was also mostly missing & the only piece left crumbly. The newer stuff has a sheet of thin plastic almost like syran wrap bonded over the insulation. I got 2 pieces like that. I lucked out and got mine off scrapped trucks. CsmDavis might still have some hoods that possibly have some left?

 

[Vintage iron]

Metal building insulation will work. there is a foam rubber that is just like the M939 hood insulation.

 

[aheilmann68]

Not sure if anyone took this thread any further but I just ordered the following and will likely be putting it in later today. Heat reflective sound deadening foam. 1" thick 54" wide McMaster # 5692T35.

 

[Cruceno]

Let us know how it works out for you. I looked over that stuff (and a few others) but I shied away from it because of the relatively low temperature rating. A0/A1 engines operate at 175-195*, and A2's at 190-200*. The link you posted rates that insulation at 225*. I'm concerned that engine heat coupled with summer temperatures would lead to a failure of the insulation.

Maybe I'm being too cautious? Anyone else have any thoughts on this?

 

[aheilmann68]

I agree with you but I figure that the actual air temperature does not fully reach that since the radiator kicks in an provides additional airflow through the motor compartment. I also went with the heat shield to aid in the possible temperature issue. It should arrive later and I think I will install it after work, I also plan on using a sound meter to take a few different readings.

 

[Cruceno]

You're probably right. I'm probably a little too paranoid about it.

Still, snap some pics of your install, and I'd be very interested in your sound readings. My neighbors have complained a lot less since I sold my M35A2 with the whistler for my 923, but I'm sure that proper sound deadening insulation would help even more.

 

[aheilmann68]

Absolutly. I was/am concerned by the temps but I do not think the installed foam is any different. They all need to pass a similar flame retardant test. I was interested in the easy to clean version that blocks 75% vs the 60% that I got but I valued the heat reflective coating a bit more.

 

[aheilmann68]

Well, I put it in. Good news is it fits. Bad news is that it did not accomplish much. I was not able to grab the sound meter we have at work for my test so I was forced to resort to an app. So any sort of data is essentially worthless and reflected as such. I saw a reduction of about 1db on the app which is barely noticeable to the human ear but I will try to get the real meter to see where it actually is sound level wise. I ordered 15 feet but all that is needed is 10 feet. Since this material is only 1" thick I may order another inch of a different foam and use this between the metal and the new layer. It did cut down the high end noise of the motor which is what I am more concerned with. With the low frequency sound (noise) that is created by the diesel motor, you need mass to make any substantial reduction and this material although nice, does not have mass.