Heater Core: 2003 S-10

greencountry05

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I'm writing this tech article specifically for a 2003 S-10 because A) I couldn't find one on the internet. B) There are big differences between almost every model and C) I hope that this will help somebody out. First thing's first, if you are the owner of a Chilton's or Haynes repair manual for the 93-04 S-10/Sonoma....THROW THIS SECTION AWAY!!! It was absolutely worthless in the removal and installation of my heater core. It may be accurate for other model years but it was no where close on an '03. The next thing you will want to do is get a twelve pack of "spinach". What the hell does that mean you say? (guess you didn't watch Popeye?) What I mean is get your favorite drink because you are definitely going to need it, I chose Rolling Rock and some Bud Light. If you're like me I also grabbed the radio to keep me company and my lap top to look up and solve problems I ran into. Most of the sockets you will need will be 10mm and 7mm with all sorts of extensions and swivels, mostly 3/8 drive and 1/4 drive. The largest socket you will need was either a 13 or 15 for the steering column.

First thing you ought to do is to disconnect the battery, don't want the airbag knocking you unconscious do ya'? Not that that will happen, but better safe than sorry right?

Next step is to drain the radiator of coolant. You can do this by either releasing the petcock valve on the passenger side of the radiator OR if your valve was really hard to get unstuck, like mine was, you can instead take off the radiator hose that is right above it and drain it that way. Make sure you have a drain pain ready or the EPA will **** a brick lol.

Now to the inside of the truck, we'll start by taking off all three of the lower dash panels. Once you have them off and placed somewhere safe, take off the glovebox and the trim ring that goes behind it. On the passenger side of the dash you will need to unhook the yellow airbag connector and the distribution block, and the little block that has several large colored wires going into it. The next piece to come off will be the panel underneath the steering column where the parking brake release is. The release cable unhooks from a spot under the left side of the dash, very easy to remove, then it should pull right out. Remove the dash bezel that surrounds the gauge cluster, headlight controls, radio, and HVAC. It is held in place only by clips and pops off with ease. To remove it completely you will have to disconnect the electrical connections by the headlights and the airbag switch (if your truck is equipped with it). Taking out the radio and HVAC is easy just disconnect all the wires and if you are afraid you will forget, just label each one with a piece of tape and pen. The steering column is held on by four bolts and then there is a collar below it that is held by four bolts. Next I would remove the speaker grilles, but be careful when unscrewing the screws because the sun has probably made the screw wells or the grille itself brittle over time. The next thing to remove will be the defrost grille but as with the speaker grilles the sun will have made it brittle and easily breakable. While trying to remove mine it cracked in one spot, I moved to another and it cracked again, I moved to another spot and it broke. But I thought, "Meh, I'll just get one from LMC." WRONG! You cannot buy this piece from their catalog so be extremely careful while taking it out. If anyone finds a catalog or parts store that sells them let me know otherwise I'm heading to the junkyard to find one.

Now, since I'm writing this off of memory I'm almost certain that once those four screws under the defrost grille have been removed and you make sure the electrical connections are unhooked the dash should fall down and swing back to remove it. Be careful with the passenger side as the hook over there can gouge your plastic trim, I'd recommend having another person to make sure it doesn't scratch up your interior, if you don't have anyone available just wrap a rag around it. The dash is not heavy, I'm a small guy and was able to take it out myself but again, if you're afraid of scratching up the interior or ripping the seat get a buddy.

The interior should look really bare by now, staring at you will be a big black box on the interior side of the firewall. If you flip up a flap at the top of the box, you can see the prize...the heater core. There are several very tiny screws in this area which require a 5.5 mm socket for some damn reason. Remove the screw underneath the black box on the right side close to the floor, the screw should be grayish in color. Theres a small actuator on the top right side of the box, it's flat, black, and shaped kinda' funny with a metal rod thing in it. Remove this and set it aside in a safe place. This actuator is what controls the flow of hot air.

Go to the engine side of the firewall and remove the two top screws on the A/C housing, they should be grayish in color. Next, to the right of the A/C housing above the engine there will be a threaded stud will a bolt, remove it. On the A/C there's a plug on the top with three tiny screws (can't remember the size), inside of this box is the resistor coil pack which you will need to unplug and move to a SAFE and CLEAN place. If you get dirt, oil, grease, or whatever on the coils you may foul it up. Down inside this hole you just made should be a bolt, it's tricky to get to, but I have small hands and was able to get it out without much trouble. I used extensions and a swivel to get it out and was able to get my hand in the hole and take it out the rest of the way to keep it from dropping down in there never to be seen again. There are two more bolts left if I remember correctly, but to get to them you will have to jack up the truck and unbolt the passenger side inner wheel wells just enough to get your hands in there. You may also have to unbolt the battery tray as I did. These bolts are just like the one above the block, they are threaded with a nut. The one that is further inside is directly behind the exhaust manifolds and should have a plastic nut/covering on it to keep it from getting damaged, or melted. Remove this and you can now get to that bolt. I do believe at this point the heater core should pull right out once the inlet and outlet hoses are removed from the engine side of the firewall.

Once you can pull the core out of the black box assembley you may notice that your aftermarket replacement is thinner, has no insulation ,and the bottom of it is square while the stock one is round. Fear not, eventhough the bottoms are not the same you can squeeze it in and bolt the flap back down securely. As for the rest of it, just put it all back together and you should be fine. Just remember to check and double check your connections before buttoning everything up. I put the battery in at two different points to make sure everything was hooked up properly. Hopefully if I left something out I will remember it eventually lol.

The last step I took, which is an extra one, was to flush the whole coolant system. I have seen many posts on the internet and talked to people in real life who say that Dexcool Antifreeze is garbage and clogs things up, namely heater cores. Soooo....I purged the system and put in plain old Prestone 50/50. How did I do this? The redneck way...I removed the water neck and took out the thermostat and stuck a garden hose in there and flushed it with water three times or until you see it running clean and clear. Next I flushed out the overflow tank, make sure you disconnect the overflow tube going to the radiator or else you'll have dexcool flowing back into your radiator lol. (trust me, I know) The nextstep is to flush the radiator as well until it is clean and clear. Clamp all your hoses back, replace the thermostat..yada yada etc. etc. Fill the radiator up with antifreeze and check your fluid levels and then start her up. Note that on the V6 model S-10 there are two drain plugs to drain the coolant from the block, one on each side. You can do it this way but it's much, much easier just to flush it from the thermostat housing.


And that is it! Took me a combined 10-11 hours off and on over the course of two days. Don't get discouraged, when it comes to being a mechanic I'm remedial, so if I can get this done so can you! And why not? Dealerships are quoting people out there 1200-1400 dollars to do this and small shops are saying anywhere from 400-800! Holy **** batman! I spent 60.00 on the core and 17.00 on antifreeze....so do it yourself and save lots of money. Hope this writeup helps. Pictures are posted below........
 
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greencountry05

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greencountry05

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Truck Model
V1500
Engine Size
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2003 S-10 Ext. Cab 4.3

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Removal of the battery and the lower radiator hose. (you do not have to remove the fan shroud but it helps)
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New heater core
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greencountry05

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Having your tools and a lap top handy sure make things much easier...
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greencountry05

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Removal of the dash panels
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greencountry05

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Pile of parts
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greencountry05

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While removing the airbag control switch this fell out, if it does do not be alarmed it only goes back in one way
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greencountry05

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Be careful removing the speaker grilles, the screw wells may be brittle and break like this one did
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greencountry05

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5.7
BE EXTREMELY CAREFUL WHEN REMOVING THE DEFROST GRILLE!!!
LMC does not carry this so it's important you don't **** it up like I did. The clips are on bothsides of the grille and there are six of them I believe. When I get home I will look again and maybe take a better picture of the backside of it.

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greencountry05

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If it gets dark keep on going
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greencountry05

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Interior should look like this when the dash is out
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greencountry05

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The bolts on the A/C housing and the hole where the resistor goes
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greencountry05

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The infamous "bastard bolts" that you have to jack up the truck and remove the fender well to get to
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greencountry05

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Engine Size
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Also, knowing how to do it now. I could easily cut my time in half because I ended up taking apart a lot of **** I didn't need to because I didn't have anything to go by.
 

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