Found the reason for gradual loss of coolant. There was a tear in the upper radiator hose where it clamps to the thermostat housing. The local parts store did not stock the hose. But there seemed to be plenty of slack in the hose, so I just cut off two inches and reattached it for a temporary repair until I can replace the hose.

The hoses are Volvo parts, but the upper hose clearly is worn and not stiff when squeezed. The disturbing part is that there is a coating of a black pasty substance in the hose liner that came off on my finger when I swabbed it. It's as if the rubber liner is deteriorating into paste. The FAQ doesn't address this condition specifically, except to note that hoses last about eight years, and that Volvo hoses seem to last longer than other brands. So I'll be replacing the hoses and thermostat soon as I can get the parts.

My question has to do with flushing the cooling system. I suspect my heater core is partially clogged, since I don't get really hot air anymore. If the hoses are shedding gook into the cooling system, what's the best way to flush it and the heater core? I'm also wondering if I should detach the heater hoses and blow out the core with compressed air as well as water. Suggestions and thoughts?

Regards,

Robert