At 12:06 PM 10/13/2002, you wrote:

>I have been  using SIERRA coolant in my '84 for past couple of years.

SIERRA is Propylene Glychol=non-spec. Use proper spec ethylene glychol
non-phosphate.

>   I am
>getting a jelly-like brown build-up on coolant reservoir, underside of
>pressure cap, and overflow tank.

This suggests that oil is getting into the coolant. Drain the oil to
inspect for presents of coolant. Pressure test the cooling system and watch
for loss, hot and cold. Do a leakdown test of each cylinder at TDC and
watch for bubbles in the coolant. If these test show no faults, drain,
flush and renew the coolant with the proper spec fluid.