Well, I am NOT a mechanic,

but I have read on the list that when a catalytic converter gets destroyed,
it will rattle inside.

To test this out, I have read that you bang on the cat with a metal rod, and
listen for a rattling "briquettes" type of sound.

Marshall Ruskin

>After a history of engine temps hovering at the bottom of the LED w/ temps
>in the 90's, our '87 GL has decided to slowly heat up.  Coolant tanks are
>full and stable, belts are in good shape (recently replaced) and we're not
>running the A/C.   What I have noticed lust recently (about the same at the
>higher temps) is a heavy rattle which seems to be originating at the
>muffler (which is rusty and sounded semi-perforated before).  The rattle
>goes away when the engine is a little above idle.  In addition as the
>engine heats (never overheated *yet*) up engine "power" & response drops
>significantly.
>My thought...The muffler is coming apart blocking the exaust flow. In turn
>backpressure on the system keeping the cylinders from being evacuated
>completely and progressively raising engine temperatures. Sound possible?
>My other option is that the H2O pump is failing (because of a new belt??).
>
>Thanks,  Chris A.
>     '87 Vanagon GL
>     '87 Honda Accord (201k)
>     '86 Honda Civic Si (236k)
>