GM Factory Undercoating

[richard5933]

When we got our bus the underside had a black coating on it - looked like black-ish paint but had a slight rubbery feel to it if you pushed against it with a fingernail. This winter it started to flake off in pieces an inch or so in diameter. The flakes are pliable, black on one side and dark brown on the other.

Since the underside of the bus is aluminum, am I correct in assuming that there is no need for concern here? We don't drive in the winter, so I'm thinking that the only real purpose for this stuff to us is maybe some sound insulation. Another thought was that maybe it had something to do with water resistance from water splashing up from the road, in which case I should take some action.

Thoughts?

[richard5933]

Does anyone have an idea what type of product GM used for their underbody paint?

[luvrbus]

You can buy it @ Auto Zone in spray cans there no difference in undercoating that I know of it's all nasty spraying it on it is rubberized asphalt,fwiw 3M makes a good product I used 3 cans last week on the RV   

[richard5933]

You can buy it @ Auto Zone in spray cans there no difference in undercoating that I know of it's all nasty spraying it on it is rubberized asphalt,fwiw 3M makes a good product I used 3 cans last week on the RV

I've used the 3M spray - it's what's inside the wheel wells on the bus. Very much like what was there from the factory.

The stuff that's on the underbelly of our bus from the factory is much different though - more like paint, although much thicker and has somewhat of a plastic feeling to it as it flakes off in big pieces. One side is black, and the other side looks more brown. Maybe the brown is discoloration, but it seems to go through about halfway through the thickness. In some ways the stuff reminds me of the very thin mica sheets that used to be used in furnace door peep windows.

I'd like to find out what the stuff was and then see if something like it is still available. It's done a good job of protecting the aluminum on the underbelly from weathering so far, but this winter it started coming off.

[MagnoliaBus]

Hi Richard,

Usually it is the "Tectyl" product that was used on gm bus and still in use by coach and transit builders.

[MagnoliaBus]

From Prevost Maintenance Information MI15-18
The same product is used by Novabus and New Flyer

[richard5933]

Thanks guys. That looks like it might be the stuff. I've ordered a small can to see how it works.

[luvrbus]

If not what you looking for it's probably going to be Daubert brand that what the military uses, its all water based now so its going to be different

[MagnoliaBus]

If not what you looking for it's probably going to be Daubert brand that what the military uses, its all water based now so its going to be different

All tectyl products are made by Daubert or under licence from them.

[luvrbus]

I have a 5 gal can of Daubert that was in the Humvees when I bought those. the friggn gun cost a fortune to use it though lol a paint brush doesn't hack it