Bag of Insulation, but why?

While wiring for a trailer I found this:



It's a thin black plastic bag with 4 rectangluar pieces of insulation in it. It was just sitting loosely over the wheel well behind the panel I removed. Why would this be there?

i would keep it in, its's there to reduce road noise.

Yeah, that'll be a bag of dope from the last owner of your XJ. Kidding. I found two similar bags of insulation behind the cargo area trim pieces just as you did, only mine were a tad dirtier than your pristine examples of MOPAR sound sappers.

I believe they are there to kill any road noise that creeps up from the rear of the vehicle into the cabin area. It is some of MOPAR's finest insulation, taken from the pulverized remains of old YJ's that never sold when the TJ's came out. They work so well, in fact, that I have ordered a couple of extra bags of the insulation to pack around the passenger area when my wife accompanies me on my next road trip. I will report the results from that experiment in a later blog.

Until then, cram it back in there, man.

i bought a honda for around and found a bag where the spare tire goes let me tell u it wasnt insulation lol

keep it in for sure i would love to have a quiet cherokee again

I threw it back in, but it was such a small bag for such a large space. I could have put another 8 of those bags in there. The wiring is done and there's no rust in the cargo area - it was a good day

yeah there should be another bag also on the passenger side as well

anyone want to buy mine? $35 shipped, I'll make it a set for $39.99....theres also something like that on the passenger side floor pan...it was cotton wrapped in plastic and grew lots of green stuff before it went in the trash...I thought briefly of UPS'ing it back to DC HQ with a note asking what the heck they were thinking :twak: but couldn't stand the smell long enough to get it to the post office...

the bag with insulation inside is also supposably there to collect moisture

DYNAMAT!!!!!

My bag of white cotton insulation on the passenger side floor pan, just under the big rubber foot mat, was in perfect shape, right in front of the huge rust hole in the floor pan. My rust hole looked like it started from the inside and rusted outward, the bag of insulation was perfectly dry and clean.

I just assumed it was sound deadener, probably a later add in, from testing, they found a hot spot where noise was carrying into the compartment and threw down a cheap bag of insulation to kill it.

DYNAMAT would be awesome, but also really really expensive. I'm amazed at some of the resto projects you see them doing on classic cars and they are totally coating the entire floor under the carpet with DYNAMAT, that must have cost $1000. I guess it may be cheaper in bulk packs for that much area, but it still has to be hundreds of bucks.

Lizard Skin is the latest product that is taking off, its like bedliner like Herculiner, but more expensive and better quality. I guess the sound deadening and protection is so good they are applying it to the floor before putting carpet over it.

UnderCoating and some cheap Dynamat substitutes have tar in them, and that gets gooey with heat and flow and mixes with carpet over it, as well as smells. Some of the more expensive, undercoating, 3M Professional is one I used, states it has NO TAR in it. That might work well, I only used that stuff for a small portion of the underbody of my XJ, but it did seem like really good stuff, a medium flat black rubber coat with no smell and felt really dense, tough and adhering to the surface like a well cured paint. If it wasn't $8 a can, I would have done the entire underbody with it.

They start on fire quite nicely while welding around wheelwells, etc. something to watch out for...

My whole truck is dynomated with Rhinolining on top of it and throughout the entire cabin area and it does wanders. You can't hear any road noise at all unless you have the windows down. So if your wanting a quiet interior its the way to go.

How much did all that dynomat cost? Is there some sort of bulk pack that is a lot cheaper? I've only see Dynamat in 24"X36" sheets for like $40. That has got to add up quick and become expensive.

It comes in bulk rolls which I figured out are just three big pads rolled in a box together, but it wasn't cheap. Also, make sure you get the right Dynamat there are many flavors.

How did the bedliner work on top of the dynamat? I would think it would crack off as the dynamt expnaded and contracted as it likes to do with the temperature?

That bag has been brought up plenty of times here on :: Might try and search next time. Hasta

EMSJEEP said:

It comes in bulk rolls which I figured out are just three big pads rolled in a box together, but it wasn't cheap. Also, make sure you get the right Dynamat there are many flavors.

How did the bedliner work on top of the dynamat? I would think it would crack off as the dynamt expnaded and contracted as it likes to do with the temperature?

Click to expand...

The bedliner is working fine on top of the dynamat no cracking or anything yet and its been in there for 2 years or so, I couldn't help on pricing tho becuase I bought it already installed with dynomat.