<p dir=ltr>So this is a hopefully helpful explanation on how to remove the heater core on a automatically controlled heater core. </p>
<p dir=ltr>This is a instruction of how I did it step by step as best as I can describe. In my opinion I strongly suggest buying a ACdelco brand heater core,  the two aftermarket products I purchased would not fit properly without modifying the housing. The acdelco core is discontinued by gm but they still have warehouses that stock them. I purchased it for $60. A quarter inch drive air ratchet will make this go a lot faster. The tools I used for the entire job were a dewalt electric impact driver, a 1/4 inch drive air ratchet, 10 mm standard depth socket, 10mm deep depth socket , 7mm deep depth socket , a 7mm standard depth socket, and one 1/4 sae standard depth socket 1/4 inch drive ,a 9 inch length 1/4 in drive extension and a 2 inch length extension .
now the first step in this process usually seems the most daunting and its the removal of the dash. you can do this in a not to lenghty process if you have a air ratchet . but a regular one works as well just it will take a lot longer.
STEP 1 you need to remove the two piece plastic under shield of the dash its tucked underneath the radio plastic screwed to the dash with a couple 7mm head screws , two on the passenger side and three on the drivers side. there is also one wing nut that hold the "passenger" section ( which stretches over to the drivers side dash ) down near the right of the gas pedal which holds pins the two sections together. there are two lights the turn into the plastic to remove the lights are for illuminating the carpet when the doors are open .
STEP 2 at this point i disconnect the battery. for safety
STEP 3 is to start removing the the trim pieces and the glove box internals
to remove the the glove box cover you need to remove the three short 7mm head screws with a shallow 7mm socket. then remove the screw pins that hold the plastic in and the two 7mm bolts the right and left sidewalls that hold the non visable support rail in place .
this gives you access to two of the main mount bolts that hold the dash on.
STEP 4 removing the silver center trim piece and HVAC switch
there are five 7mm bolts that are along the underside of the top piece of the trim. the bottom is held in by spring clips so those just need to be gently pulled on to remove them from the dash they stay connected to the center trim peice. to remove youll need to shift the gear selector into 1st gear (all the way down) and pull back the rubber fascia piece to clear for the trim piece to be removed . once all screws are removed pull gently back on the whole bottom side of the trim to remove it and slide up and around the steering collum. this will give you access to the four 7mm bolts that hold the hvac switch in the dash that will need to be removed. once bolts are removed the there will be two connectors one five pin conector for the fan speed control. and one for the rest of the hvac switch unit, this connector will be encapsilated under some foam. just peel the foam back for access.
STEP 5 now for the lower dash unit, there are about 7 or eight screws along the dash that hold this piece on. once screws are removed the piece is free and the radio is connected by four bolts and three electrical connectors in the back plus the antenna cable and the cigarette ashtray has a light and 12 volt connector so this will also need to be removed from the assembly to avoid damage.
STEP 6 dropping the steering column is a easy task you just have to be careful there is a clip that connects a small cable to the gear select indicator that just needs to be removed and marked for the correct replacement of the clip. after this is removed there are four 15mm head bolts that need to be removed to safely drop the column down on the seat.
STEP 7 remove the 6 torx screws in the upper main dash (t20 i believe) there are two mounted in the sides of the dash and two in each speaker cover. remove the speaker covers and the center defrost vent cover. the vent cover has a sensor that just turns out like a light bulb socket.
STEP 8 youre ready to remove the main dash bolts and screws this is the final step to removing the dash ( you only need to get it pulled back )there are five long 7mm bolts in the upper side near the windsheild one center and worked out from there . there are six 10 mm bolts . two under the cluster where you droped the column, rwo are on the bottom corners of the dash, two are in the left side of the glove box space that you removed earlier.
at this point the dash is free but stuff is stil connected. the parking brake cable will need to be released from the mechanisim which is not hard just take a pick and slide the cable ball out of its slot.
also the headlight switch connectors are very fragile and hard to remove from the dash so this is why i chose not to remove them and just get the dash free.
once you pull the dash back from the car the dash is connected to the vent tubes you will just needs to remove these before pulling any further. there are only two you have to worry about.
STEP 9 is to remove the automatic controller from the side of the heater core case. this is on the side from behind the dash . there are a few wire connctors to get out of the way however the ones conncted to the controller i left on and just layed the box to the side. the bar that connects the controller to the movable flap needs to be removed, just turn the plastic clip off of the metal hook bar and slide it out of the flap. be sure to mark controller bar point on the screw side of it cause it will most likely fall out of place.
there are three 7mm bolts that hold the controller in place . the computer and all other engine wire connections are to the right so take extreme caution. i removed everything but it is not necessary you can just remove the controller.
STEP 10: is to remove the side cover to access the heater core itself. . there are two 7mm bolts that hold the cover on. once removed the cover moves to the right and un hooks from the back and can be slid off to expose the heater core and mount.
STEP 11: removal of heater hoses do not remove the heater core mount yet it will hold it in place while removing hoses. coolant will leak from this when performed so be sure to have a drain pan for underneath the car . there are in a very tight location by the A/C accumulate and passenger strut tower. you will have to have a long radiator pick to help. be sure to check your hoses for cracks or dry rought be sure to replace if found. the stock clamps use a 1/4 sae socket to remove i used a long extension to reach them. i replaced the clamps with new ones that use a 8mm socket they are a little stronger. if you are using the same hose and clamps be sure to get the clamps in the same position if possible to be sure of a good seal . use the pick to remove them back.
STEP 12: remove the clamp that holds the heater core in place under the dash . it is a little metal clamp that holds to the cased with two 7mm head bolts and the heater core will slide back out of its position .
STEP 13: install new heater core.
connect heater hoses and reasseble the controller and dash to its original locations
fill engine with water/antifreeze 50/50 mixed coolant top off
reconnect battery
run engine with the heater on and idle... check for leaks coolant level will drop top off to proper level
this filling process can take up to a half hour
run vehicle with the radiator cap off for a short amount of time to bleed air from the system or else overheating can occur. like 5 minutes or so.
Thank you for reading i hope this helps with the air tool it probably took me a total time of 3.5 hrs
be safe and save your self a bunch of money on this job with not to long of time
like i said the airtools help with any project like this really.
