How to replace heater core on Chevy Astro?

Its for 1994 models and above.

The procedure is as follows.
Some  non experienced car repair techs,take out complete dash to replace faulty heater code,but its actually not required.

The details are below :----





The front heater core is located on the right side of the passenger compartment, under the dash.
Disconnect the negative battery terminal from the battery.
Place a catch pan under the radiator, open the drain cock and drain the coolant to a level below the heater core.


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

Remove the radiator overflow coolant bottle and the windshield washer fluid bottle.
In the engine compartment, remove the inlet/outlet hose clamps from the heater core. Remove and plug the heater hoses to prevent coolant spillage.
From inside the vehicle, remove the engine cover to provide extra room.
From under the dash, remove the lower right filler panel.
Remove the distributor duct, for extra room.
Remove the heater-to-cowl bolts and the heater assembly from the vehicle. In some instances this may not be necessary.
Separate the cover plate and the heater core from the heater assembly.

To install:
Assemble the cover plate and the heater core to the heater assembly.
Install the heater-to-cowl bolts and the heater assembly in the vehicle, if the entire assembly was removed.
Install the distributor duct.
From under the dash, install the lower right filler panel.
From inside the vehicle, install the engine cover.
In the engine compartment, install the inlet/outlet hoses on the heater core tubes.
Install the radiator overflow coolant bottle and the windshield washer fluid bottle.
Refill the coolant to the proper level and check for leaks.
Connect the negative battery cable to the battery.
Start the engine and recheck for leaks after it has reached operating temperature.

REMOVAL & INSTALLATION

Front Core

See Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11

Fig. Fig. 1: The heater core has its water connections in the engine compartment

Fig. Fig. 2: With the engine cover off, the trim panel bolts are accessible

Fig. Fig. 3: Remove the trim panel to access the heater box

Fig. Fig. 4: The air distribution duct is mounted in front of the heater box

Fig. Fig. 5: Note the seal at the top of the duct. Make sure it is in place when assembling the duct

Fig. Fig. 6: The side cover is held by 2 bolts

Fig. Fig. 7: The side cover is also gasketed. Check its condition once removed

Fig. Fig. 8: The heater core is held by small bolts and molded-in brackets

Fig. Fig. 9: the core can be separated from the heater box without removing the entire assembly

Fig. Fig. 10: Mounting scheme of the front heater module

Fig. Fig. 11: Exploded view of the front heater module

This details will help.

Thanks.

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