I have a 93 silverado 4x4 80,000 miles on a crate motor Direct fan no clutch. last week the waterpump went I replaced it and a new thermostat, yesterday I had to cancel a job because it went to around 265 the top hose was colapsed. I got it home with out going inn the red when I opened the system there was alot of brown slim so I removed the new 195 thermostat and drained the system flushed with water till clear then ran flush cleaner for 4 hours put a new 180 thermostat in it with a new top hose, filled the block first then the radeator ran it for 1/2 hour looked good ran the rpms up and the hose colapsed opened the thermostat housing and thermostat was wide open it is acting like it can not get enough water through the thermostat . Ran it at high rpms with no thermostat no colaps

 

If the hose collapses then the rad cap is bad.