We had a Class C on a 1983 E350 with the 460. On a hot day, running along the level interstate using cruise control, the FAN would kick in as we climbed the gradual grades for overpasses. It would build quickly to an exhaust-like sound then fade away again when we reached level ground. First time I thought we were being passed by a motorcycle gang.
We also had exhaust manifold leaks. In our case, the stamped steel gaskets rusted out and the manifolds warped. I was fortunate to get every fastener out. Both sides, 8 each, all 16. In our case, I had the manifolds re-surfaced and put them back with new stamped gaskets and new bolts.
