That's what I thought too. Don't know if it is possible to melt a
thermostat housing. It may be possible if there is no coolant flowing
through. I have heard pistons melted when excessively overheated.
On my 1.9 the thermostat housing is lower than cylinder heads. If there
is any coolant in the system it will be there in the thermostat housing.
But if it did happen as Jim pointed out I guess it is possible no
matter how it happened.

If the thermostat housing is indeed melted I won't trust my cylinder
heads and piston/cylinder liners any more. That's at least serious
short block rebuild at least. From the photos I am not convinced
that it is melted. But the amount of rust/corrosion is not pretty.
I guess I am extremely lucky to be in California. I have not seen
any engine on any car in California in such a rusty shape.

David

--- Mike Collum <collum@verizon.net> wrote:

> Have you considered that it might be black goop of some sort ... like a
> sealant?
>
> Mike
>
>
>
> David Kao wrote:
> > I think it is corossion. I don't think anything is melted.
> > To melt a thermostat housing the pistons and the cylinder heads
> > had to be melted first. Seeing on the picture and seeing the real
> > thing can be very different. So this is just my opinion.
>