Hood insulation pad

Hi Gentlemen!

I know this is an old thread (Feb-Mars 2020), and maybe this subject came back couple of times (also found this conversation), but I it is still not clear to me:
Is hood insulation worth the effort (and cost, 60$-180$), against engine compartment noise?
Or is it  mainly heat oriented?


Bronco Graveyard indicates the two (heat and sound):
«Under hood covers include heatshield barrier insulation panels to protect painted surfaces and to reduce the vibration and noise produced by these large body panels from entering the passenger cabin.»

I am wondering if it has a really noticeable effet on the passengers comfort...


Somebody tried it and could share his experience?

Good question, Jeff!  I've never seen one either, but then I've not been around the diesel trucks.  But I might want to put one on Big Blue to further quieten things - if they work.  (I'm not at all worried about the paint at this point in time since it is awful.)

So I'm going to tag Scott/kramttocs as he said in that other thread that it was being discussed elsewhere.  Maybe he can supply a link so we can read their comments?

Thanks Gary!

Most of what I am going to say is opinion/speculation* and trying to recall what I found when I looked into this awhile back but it is an interesting topic since heat and noise remediation can make a huge difference from what was provided stock.

I think the other forum discussion revolved around the holes in the hood. As you mentioned, Gary, I believe it was a year thing with the later years all having the holes (used the same mold across engines). I am away from home at the moment so just on my phone but will try to find that external thread later.

As for heat and noise here are my non-laboratory-backed thoughts for GAS engines :

1. The hood insulation wouldn't pay off except for looks when opening the hood. Personally, I'd like the Ford embossed version that LMC can no longer legally make/get just for the looks. I think there are better ways to address heat and noise than touching the hood.
2. If wanting to take a diesel-only feature I'd grab the plastic/matting pieces that bridges from under the dash front lip (where the courtesy lights/glove box hinge screw in). This would seem to have more of a benefit to the riders. This would be a super easy addition that would have some benefit.
3. The biggest roi would be addressing the firewall. Dynamite, heat mat, xmat, take your pick. Installing this behind the factory mat makes a huge difference (scientific equivalent of arms stretched out 'this big') for both heat/noise. Same goes for the floor pan, door skins and roof.
This would be the most involved since the dash has to be removed.
Later trucks and like Gary's underhood HVAC spaceship (to steal Jim's description) used insulation on the engine side of the firewall in the center. This wouldn't be too involved as long as it could be adhered/fastened well.

Thinking of the engine heat on the hood itself, I just can't believe it's something we need to worry about in a typical situation. Aside from catching on fire cases, I can't say that I've seen hood (paint) damage that I'd attribute to normal engine heat.
Would be interesting to capture some external hood temps from members after drives as well as from those in the hotter states from just sun exposure.

I am not, and wouldn't push this on anyone but since it does relate - I am happy with having my electric fan controller kick the fans on even after the key is off if the temp gets hot enough. This goes a long way in reducing heat soak and overall underhood temps after engine shutoff.


Interested to hear thoughts from others who have maybe found similar or different results/opinions.

* I did some temp readings on my 86 before and after doing the floor work specifically around the areas above the exhaust runs. I don't think I recorded the numbers but do know it was significant. The noise is more comparing my stock interior 80 to the 'improved' 86.


From my dads 94 Powerstroke showing the engine side insulation:

Side note: this is basic audio science, not automotive specific, so take that as you will.

For noise specifically, a hood mat could help a lot depending on the construction.  If it's a sound barrier don't expect much.  If it's made for sound absorption  it will help, possibly quite a bit.  We all know sound is just wiggly lines, and if you can break up and flatten those lines you do reduce the sound you perceive.  Sound absorption will act as if the sound coming from the engine is reduced.  A sound barrier will make it a bit less noisy outside the truck, but so much sound still comes out the front and bottom that it wouldn't do much imo.  And inside the cab it would help with the windows down but only then and only if the engine noise is significantly louder than the other noises you hear like wind and tires.

Agreed - exterior to the cab improvement is all I could think of that the hood mat  would help with and like you said, other noises often negate that.
Good point in the absorption but do you think that significantly comes through the hood and into the cab? My thought was that any noise going 'up' through the hood wouldn't be noticeable through the windshield while going down the road. Maybe that's a bad assumption though?

Yes, it is audio science that absorbing sound waves reduces the amount/strength of what is left.  Many gyms  have large absorption panels on the walls, not to prevent the waves from going through the walls and getting outside but to reduce the amount of noise within the gym.

So if we liken the engine compartment of our trucks to a gym, if we add absorption material to the hood then the amount of noise in the engine compartment will be reduced.  And if that is true then there will be less noise to penetrate the firewall.

That's not to say that it wouldn't be helpful to have the other sound control features that Scott listed.  But they will be even more effective if there is less noise because of the hood absorption pad.

Just to put this out here...

There was a exterior sound reducing package option that was offered for our trucks.

Not all trucks got this package.  

My 1981 has it and it definitely helps.  

You can see the Firewall sound mat above the carpet on the right side of the heater really well, and above the carpet on the left side if you look closely.



There is also a extra door "seal" above the window and vent window for noise deadening. I do not have a picture of that though.

--- ---


So if your truck does not have these, I'd start with those and work up.

Hope this helps.



 

Thanks for adding the photo. That firewall mat is the factory one I referenced. Pretty sure it was standard equipment though (on all vehicles). You are right about the extra package option though and it does go a long ways for cab comfort noisewise.

Like Gary said if you absorb sound you reduce the total sound.  You'll be grabbing sound that might have bounced back down and gone out the bottom even.  It's not something I'd bother with myself (I've cut 3 holes in my hood after all) but when it comes to quieting a car down you do everything because it all adds up.

kramttocs wrote

Thanks for adding the photo. That firewall mat is the factory one I referenced. Pretty sure it was standard equipment though (on all vehicles). You are right about the extra package option though and it does go a long ways for cab comfort noisewise.

I've seen a few without the Firewall mat. Cannot say if the previous owners removed them or not however.



-------------------------

Another piece of sound or wind barrier often removed by previous owners . . .

Underneath the door panels there was a thick paper (later plastic) shield to help seal the access holes in the doors. Often discarded when working inside the doors.

Sound deadener sprayed on the inside of the door's sheet metal. New Door skins and door shells would not have this.  Knock on the door's lower sheet metal, does it thud or does it ping?

Underneath the floor mat or carpet, cork and foam insulation, extra to the heat shield on the passenger side. A lot of the time this got wet, molded and discarded by previous owners.

Not sure what was standard or what was part of the reduced sound package, but hopefully it gives people the idea of where to look. Where it might be missing on their trucks.