So I have finally gotten around to trying to quite the van down some and make it a little more passenger friendly. Van is an '88 e250 7.3 IDI with a c6/DNE2 trans.

First step was to add a muffler to the exhaust I had built last summer. It had been straight piped for the last year and the drone was pretty annoying on road trips. Towing anything made it get real loud real quick.


Then I pulled up the carpet on the interior. I added 2-3 layers of commercial grade rubber roofing against the bare metal floor and another layer of carpet pad.


Today I removed the stock doghouse insulation to add another layer behind it.


I purchased this at Summit. It is reflective with an adhesive tar like backing. The box said door kit, but it said it was also to be used on hoods and firewalls.


Coated the inside of the doghouse and then put the stock insulation back on. Once I cleaned the inside of the doghouse it seemed to adhere well. I am about halfway done in the pic. One box was enough to completely cover the inside of the doghouse.


The van is definitely quieter. The muffler tamed the exhaust noise and drone. I no longer hear it while I am cruising at highway speed. I will have to wait to see how it sounds with a load attached to it. The interior insulation seems to have reduced the engine/road noise. At highway speeds (65-75mph) it is still there, but it has definitely dulled it. The radio volume is about half of what it was before in order to enjoy the music and the biggest interference with talking is the blower when the AC is on MAX.

Next step will be pulling the interior panels and ceiling covering to add wall/ceiling insulation.

Interesting observation though....the van was designed back when the national speed limit was 55mph. At 55-60mph it is extremely quite. IT would appear that at about 63-64mph the rpms get high enough to raise the engine noise considerably.

 

Adding the muffler to the exhaust system should indeed tame that at-speed drone---BTDT with a '97 E250 gasser with the catalytic converter removed, straight pipe cobbled in. It sounded like a bad muffler even with moderate flooring and roof/sidewall insulation. (Selling that van off was the "cure" )

In fact the simple act of adding a full plywood floor---no insulation underneath does a lot to tame noise coming from road and bottom of the van.

Side wall and roof insulation does even more to silence the noise too. I've used a combination of unfaced fiberglass batts plus glued-on radiant barrier insulation (100% coverage) on those areas.

Adding the fiberglass inside the rear and side door shells reduces noise even further. Of course door-wise make sure they fit tight to the body, all seats fat and plump, hinges/latches also fitting/closing well.

Now if all that's not TMI I'll be interested knowing how that asphalt-based sheeting holds up to the under hood temps. Despite the packaging claiming its suitable there I'd be skeptical but hope it works. Please keep us updated on that.

Good progress though!

 

I will let you know if there are any heat issues. The description says it can handle heat from -30* to 550*F. Lets hope they are not exaggerateing.

I plan on using the unfaced matt insulation for the wall/door cavities. How did you handle the doors that have windows that go up/down, such as the front briver/passanger one? I would worry about the insulation binding up with the window mechanisms.

 

I simply glued a double layer of radiant barrier insulation to the outer door skin, from inside the front door shells. That along with keeping the thickish plastic sheet attached to the door under the trim panel will reduce a lot of noise.

The radiant barrier stuff works as a sound deadener too, kills off any drum head-like vibrations. For the most part though the front doors don't transmit much road noise so fiberglass inside them wouldn't work as you cite plus its not that necessary.

HTH

 

Thanks. I plan on doing the radiant barrier stuff against the metal everywhere I can. Fiberglass insulation behind the wall/door panels and maybe a layer of the radiant barrier or thick plastic behind the door/wall panels to seal the insulation in. I know everyone says that I shouldn't worry about any fiberglass insulation particles floating around once the panels are up, but with it being my family hauler I am taking the route "Better safe than sorry".

I am thinking about pulling the dash so I can add sound deadening to the entire firewall. There are large areas I cant reach, just don't know how much of a head ache it will be. With the van beong an '88 and no ECU I don't think it should be too bad (minimal wiring). I could also leave the dash and just try stuffing insulation into it wherever I can.

 

IMHO you're chasing the wild goose trying to insulate the dashboard area. Apart from its difficult access you're not really getting a lot of noise from there.

The lower windshield where it meets the moldings and cowl area have been known to be noisy due stiff headwinds----your year is even less aerodynamic than the '92's and later. In fact the windshield itself can transmit a lot of unwanted noise to the inside of the cabin but that's just part of owning an older van.

 

Maybe. I agree that pulling the dash could be a pain, so it may not be worth the reward. However, most of my noise (or what I hear from the drivers seat) is not road, exhaust, wind or hollow metal drone......it is engine noise. This probably is due to it being a diesel van instead of a gasser. On top of that it is an old mechanical NA diesel, so it is even louder. Sound deading on the doghouse helped as well as on the floorboards as high up the firewall as I could get it. That still leaves a lot of area behind the dash that could be a weak spot, or the dash could be blocking as much noise as can be blocked.

I can get into the dash pretty easily. I remove a few screws and can pull the light switch area, the cluster and the large wood grain area where the climate control and radio are. I have considered pulling those pieces and seeing if I could stuff some kind of insulation in all the crevices in the dash as a test run to see if it would help. The most complete method would be to pull the dash, coat the firewall with some kind of adhesive back deadening material and then filling the empty space in the dash. The pic isn't a great view of what I can easily remove, but you can get the idea.


If I end up doing the trans swap I am considering, c6/DNE2 to E4OD/DNE2, it would significantly drop my engine rpms at hwy speeds. I would go from running at 2133rpms at 65mph to 1514rpms at 65mph (This is what I currently run at 46-47mph). Currently, up to about 55-60mph engine noise is very minimal. It jumps drastically between 60-65mph. Considering my van was designed when the national speed limit was 55mph, this would have been perfect. Problem is that now the speed limits are mostly around 70mph in my area.

 

Those diesel motors change everything----all I know about them is I'd never have one!

Good luck with making progress on all this though---will be interesting seeing how you work this out.