I have a 99 GMC Suburban K1500 4x4 5.7L and am still having problems with the rear heat. I replaced the heater control valve due to the plastic snapping when I moved one of the hoses. I got the hcv solenoid working so it draws vacuum for the hcv. I flushed out the rear heater core and it started flowing fine. Now, here is the kicker. I connected all the hoses and when the heater control valve is actuated, the heat up front goes from hot to warm or cold. The heat in the rear is still blowing cold! When the hcv is off, the front goes hot again. The only other thing I can think of is that the line(s) to the rear heater core are plugged, unless the rear heater core is plugged again. The system is just not that complicated of a system, but it is frustrating me that the rear will not blow hot. Any thoughts are much appreciated. Thanks.
Monday, October 24th, 2011 AT 7:10 AM