INLET WATER TOO HOT

 Your standard everyday pressure washer pump is not designed to pump hot water.  Pumps are cooled by the incoming water.  Most pumps can tolerate water up to 63°C (145°F).  However at these inlet temperatures there is no room for water heating while the pump is on bypass.  

Overheated pumps will chatter as the water reaches excessive temperatures.  Seals and valves will melt and ceramic pistons will crack.  It's always a good idea to install a thermal relief valve on your pump.  Installed on the inlet side of the pump they open up when the bypass water reaches at 63°C (145°F).  

It's never a good idea to let the pump reach these temperatures.  A cool running pump will last longer.  If you need hot water to clean get a hot water pressure washer or module.  Click here to see various types of hot water washers and hot boxes.  

General/Interpump make hot water pumps that will accept up to 180F, but you need a large boiler to keep up with them.