Marty,

I only hose I've ever had fail on any of my Bricks was a firewall heater hose, as well. I now just replace them when ever I do the main hoses/ Tstat etc. The hardest part for me was removing them. I found cutting a lenght wise 1"-2" slice on the old hoses at the connection allows me to peel them off the pipes relatively easily. I then clean the pipes with scotch bright to clean off the accumulated crud before installing the new hoses. If you use OE Volvo hoses, which do run more than aftermarket, you will likely get eight to ten years/ 100K service out of them. The outlet connection from the head beneath the intake is for me the hardest connection to deal with. I've found loosening/tightening the clamp using a small socket /short extension and 1/4" drive ratchet from the passenger side allows reasonable access between the intake runners. These hoses are a bit of a PITA to change but I'd rather do it in my garage as part of preventative maintenance than, as some have pointed out, on the freeway in the rain. Just my $.02