Having problems with your 1999 GMC Jimmy ?
Heater core assembly - 1999 GMC Jimmy
- Remove the front dash panel by turning the lower screws in a\015\012counter-clockwise direction, then unscrewing the single bolt on the lip\015\012of the instrument cluster and pulling the panel out. Remove the rear\015\012wiper switch and the 4x4 switches, if applicable. Lowering the tilt\015\012wheel will allow the panel to be totally removed. \015\012
- Remove the radio, headlight switch module and glove box by turning their screws in a counter-clockwise direction. \015\012
- Remove the main dashboard by unbolting it at the front, between the\015\012windshield and firewall. There are six to eight bolts holding it in,\015\012and, once they are removed, the dash can be pulled away from the\015\012firewall. Be careful not to pull too much, as the wiring harness could\015\012become damaged. \015\012
- Drain the coolant system by turning the drain plug on the lower left\015\012corner of the radiator and allowing the fluid to fall into the drain\015\012pan. Uncapping the radiator can reduce the internal pressure. \015\012
- Remove the heater core hose, on the upper left of the engine bay by pinching their hose clamps with a pair of pliers and pulling them\015\012off. Some models will have screw-type hose clamps; turning them\015\012counter-clockwise will loosen them. Age and heat may have stuck the\015\012hoses to the core nipples, and the hoses can be cut right at these\015\012nipples if necessary. Leave enough hose to reconnect the new core. \015\012
- Unbolt the heater core's mounts with a socket wrench in a\015\012counter-clockwise direction. Once the bolts are free, the heater core\015\012can be maneuvered toward the windshield and slid out. Some coolant may\015\012splash out, so have a towel handy. \015\012
- Replace the heater core with a new one by sliding it into place and securing the mounting bolts. \015\012
- Reconnect the heater core's hoses, turn the radiator's drain plug\015\012clockwise to close it, then refill the coolant system with a 50/50\015\012percent mix of coolant and water. \015\012
- Reconnect the dashboard to the firewall, then replace the front dash\015\012panel and fasten its instrument cluster screw and bottom bolts. \015\012
- Crank up the Jimmy and add coolant until the heater core is filled and blowing hot air. \015\012
- Replace the radiator cap.
Repair Help & Product Troubleshooting for 1999 GMC Jimmy
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