How do I replace a heater core in a 1990 s-10 pickup

Park vehicle on level, hard (concrete) surface.
2. Block the rear wheels of the vehicle to prevent vehicle from
moving in either direction and set parking brake.
3. Remove front bumper by removing (2) outer 13mm brace bolts
and the (4) 18mm bolts from front of bumper.
If the vehicle contains a crash bar below the bumper, it must be
removed. To accomplish this, remove the (6) 21mm nuts.
While supporting the bumper, disconnect the (2) lighting harness
plugs and wiring harness from bumper (if applicable), and the (3)
plastic push clips in the rubber shield. Carefully remove bumper,
making sure not to scratch the paint on the front fenders.
4. To make access to spring eye bolts, remove (2) 8mm bolts at the lower corner supports of air conditioning
cooler and remove supports. See Illustration 1.
5. Remove the track bar bolt (30 mm) (save for later use) on the
driver side of the frame mount (see illustration 2), and the tie rod
end from the pitman arm.
6. Raise the front of vehicle and support with jack stands on the
frame behind the front springs.
7. Remove the front wheels.
8. Support the front axle with a floor jack.
9. Remove sway bar end links on both sides. Save the 15mm bolts,
to use for reassembly.
10. Remove front shocks (saving bolts for reinstallation).
11. Carefully bend brake line bracket at frame to horizontal position
(see illustration 3).
12. While supporting front differential with a floor jack, remove driver
side U-bolts.

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REMOVAL & INSTALLATION
Disconnect the negative battery cable.
Position a drain pan under the radiator, open the drain cock and drain the cooling system to a level below the heater core.
NOTE: Plug the heater core tubes to avoid spilling coolant in the passenger compartment during removal.


Disconnect the heater-to-engine coolant hoses from the core tubes on the fire wall, in the engine compartment.
NOTE: On some early model vehicles, the cabin light mounted under the dash may interfere with cover removal. If necessary, loosen the retaining bolt and reposition the light housing with the wiring attached.


From the passenger compartment (under the dash) remove the heater core rear case cover-to-cowl screws, then remove the cover from the vehicle.
NOTE: On a few of the early model vehicles covered by this manual, some of the heater core cover screws may be partially/fully covered by the dashboard. Be sure that all are removed before attempting to remove the cover. If necessary, unbolt and reposition all/part of the dashboard for better access.


Remove the straps or brackets from each end of the heater core.
Carefully remove the heater core from the cowl and case.
Installation is the reveres of removal. Run the engine at normal operating temperatures and check for leaks.

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