On the brass part of the pump there are three bolts (soft metal) on the underside. These bolts blow out after half a minute of engine run time. Any ideas? Garden hose and engine are on but no water comes out of gun (with gun trigger on or off). After a few seconds, one of the three bolts blows out of the bottom. When garden hose is connected and pressure hose is removed, no water comes out of the pressure hose bib. In the past, water would come out of the pressure hose bib. Unit is 2 yrs old.