Why is black dust is coming out of my heater/AC vents
 

Black dust and little bits of what looks like foam insulation is coming out of the vents of my otherwise pristine 1991 350SD. It accumulates on the carpets and sills next to the front seats.

Makes a real mess!

Has anyone else had this problem? Is there something I can do about it or do I just have to wait until all the insulation is gone.

I was thinking of ingesting some kind of goo into the ductwork that would seal this stuff in place, but I'm afraid that anything I would use would be very toxic and/or gum up the working parts and sensors.

Suggestions, sympathy???

John

1st thing i would test is your hood pad - if you have one that is. it may be toasted from heat and crumbling, sending that material through into the car's cabin.

when it happened in my car i removed all
hood pad material and the problem ceased.

here's what caused the material to go into the cabin..
 

..

Hi John.

I'm not sure if you have that sensor on the dash
like some w123's do.
If you do,then remove the interior of the glove
compartment,with a flash light look to the middle
of the dash.
You should see a foam hose going to the sensor,
it is probably falling apart.
Easy fix,if it is.

Louis.

3 areas you can get "foam" particle from. Check the 2 easy ones because the 3rd is inside the evaporator/heater box.

1. Hood pad. Look at it and if its falling apart then that is probably it.
2. foam tube located in the the glove box area. Have to remove the glove box internals to see it.
3. There are foam sheets on your flapper units inside the heater/evaporator box. They do deteriorate and pieces get blown out the vents.
If 1 and 2 are ok then don't worry about it. It's the foam sheet inside and you don't want to remove the heater box for this. The
center consol and dash have to come out for this job.

Heres a picture of my unit once I got it out to replace the evaporator. As you can see my foam had fallen apart after 22 years of life in Texas.

Dave