If by saying hydraulic outlets are set wide open, you mean lever for oil flow is set wide open, that may be your problem. On my 4450, oil flow lever for outlet driving pump is on almost the slowest setting. Procedure for setting flow is to put flowmeter on sprayer to wide open and then set oil flow to where pump only produces about 70 pounds of spray pressure max. With flow wide open, its possible to create enough pressure to blow things up on sprayer. My hydraulic hoses both just plug into outlet. Have to shut pump off by going to float. These settings pertain to my great plains sprayer, but I assume summers would be the same. May be way off base. Your owners manual should cover this.