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Old 05-20-2015, 11:34 PM
striker2237's Avatar
striker2237 striker2237 is online now
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Default Comprehensive "mega" guide to 3rd gen heater core replacement.

Well I promised a while back that would start making highly detailed guides for major and semi major repairs and upgrades that I perform on my truck, today is the first installment in this "series"

The guides will share a common format that I will adjust based on your input/complaints

First part is a general warning and disclaimer so that you all understand that my advice is no the final word and that safety is YOUR job and while I will try to remind you of it it's not my job in the end. Also while I try my hardest to provide as accurate advice as I possibly can I am not technically trained for this so I can't be liable for your truck blowing up/falling apart/killing things/spontaneously combusting as a result of you using the information posted here.

Now, for the first of hopefully many guides on the glorious 3rd gen ram!


Now as I'm sure most owners of older vehicles or ones who came equipped with corrosive coolant or were just plain unlucky know, a leaking heater core is highly annoying and a potential hazard in winter. (defroster wont work well)

In my case it is the former, I had a pinhole leak resultant in my dad never once changing the coolant in over 150k miles. This resulted in a faint, brief smell of anti-freeze to be experienced by passengers when the heat is first turned on and also conjured up worst case scenarios of the core exploding and ruining the interior for the owner (me).

This motivated me to replace it, the tools that are required are as follows.

1. A ratchet with pivoting head available at your local harbor freight (Now before you all go nuts on me for suggesting a harbor fright tool, I have access to both snap-on and MAC tools at work and both me and my boss use one of these because it is simply better)

2. A 10mm Deep Well socket, most of the fastener we will be dealing with are 10mm and require the deep well to undo

3. A 13mm Deep Well socket, the major bolts that hold down the dash are of this caliber and also require deep well functionality

4. A 6 inch 3/8 drive extension, this is necessary to undo some of the steering column bolts and makes life much easier when unbolting the HVAC from the body

5. A 3 inch 3/8 drive extension, this is not needed but extremely useful

6. A 3/8 inch drive pivot adapter, this is needed to remove the upper dash bolts

7. A 3/8 drive 8mm socket, this is needed to remove the ECU and secondary upper dash bolts and any bolts that you would normally use a screwdriver on that are being "uncooperative" (you striped them)

8. Both types of screw drivers and mid size, not the small ones not the freaking huge ones (cross and flat)

9. One really really small flat screwdriver or a good knife, used to open 4 access ports in the trim

10. A trim stick, not needed but if you like having scratch free trim panels without and broken tabs use this (Bonus points for using a lexus one!)

11. A magnetic tray, not needed but I will laugh when you come back asking where to buy that bolt you lost

12. Gloves, not needed if you like/don't mind corrosive/harmful substances in direct contact with your skin

13. Hose clamp pliers or normal pliers if the purpose built ones are not available

14. 1/2 gallon of anti freeze, since we are opening the cooling loop we need to ensure we refill the system with the CORRECT FACTORY COOLANT, well that is if you like the system not corroding or over heating....if thats not a concern fill it with coolaid for all I care!

15. 8 inch automotive pribar, not needed but you might break your shift cable without one.......87$ to get a new one from mopar.......(only place you can get one if you just so happen to accidentally kill a customers cable)

16. 3/8 inch drive air powered ratchet, most certainty NOT needed but will allow you do get this whole job done in under 3 hoors

17. Quick connect fitting dis-connectors.....I don't know the real name dang it!

18. New heater core...........duh, you should know's why we are here after all! Use a mopar one or a REALLY nice aftermarket one so nothing blows up on you

19. Penetrating oil, always have this.....never know when it will com in handy, oh and drinks, always have drinks on hand......

Okay, got all that? Good, lets begin! The way this is going to work is I'm going to post a photo album ( and I will go picture by picture and explain to you what to do, sound good? Cool. Now go move your seats ALL the way back, done? Cool.

Pictures 1-3 are to show what everything is supposed to look like before/after everything is done, top trim peace (spelling FTW) was removed prior to anything else. This is done by GENTLY pushing a trim stick into the gap between the top panel and dash and popping each clip out one by one then pulling it out toward you to undo the 2nd set of clips. Don't shatter a clip like I did by pulling sideways on the 2nd set.

Picture 4 is what you should see after pulling the panel that is by your knees down from the top then undoing the two small screws near its bottom edge and moving it to safety in the back seat/bed, then undo the two screws holding the hood release/OBD2 port bracket and move it upward to unhook it, then set it aside and remove the OBD2 port by pressing the two tabs on it in.

Picture 5 is me remembering to disconnect the battery, you don't NEED to do this but an airbag might blow up in your face if you don't....up to you. Oh and if you don't know how to do this without shocking yourself then I ask you stop reading as you will most likely hurt yourself attempting anything beyond this point.

Picture 6
is the shift cable sensor cable disconnection, pull the red tab toward you then press the black tab down to release

Picture 7 is the OD lockout cable removal, simply press down on the white tab to release

Picture 8 is the shift lock sensor disconect, you need to slide a red tab you can't see (top of unit) from the front of the car to the back to unlock this then press the while tab on top of the connector to release the wiring harness

Picture 9 Is a closeup view of the shift cable linkage, you MUST remove this very carefully as it is plastic, inset the pry between the black link and the column and GENTLY apply force to pop the link off the ball

Picture 10 is the driver side of the dash access panel, you need to remove this can I used a REALLY small screw driver to get my trim stuck under the edge, pull upward near each of the 3 tabs one at a time and DON"T get violent as these tabs are plastic and will shatter

Picture 11
is the two main screws under the access, the 3rd is slightly below them (NOTICE, my truck is a fully loaded laramie model so I have my fasteners in a slightly different location than the more common SLT (to accommodate all the extra electronics). For the SLT the 3rd screw is slightly above the parking brake lever inside the drivers foot-well) Do the same on the passenger side and the bolts are in the same place, 3rd bolt is in the "SLT" location for all trims but on the passenger side so there will be no parking brake in the way. All the main bolts are 13mm

Picture 12 is where you should insert your nice lexus trim stick to begin removing the inner trim panel, work the stick slowly to each tab and give a moderate upward tug to undo each one, when you get to the front part use one hand to grab the round flat part that goes into the foot-well and the other to pull at the top (top is shown in picture 13) Do the same on the passenger side

Picture 14 shows the parking brake linkage, flip that orange tab downward to unlock it and then move the lever toward the passenger side to unhook it (picture 15)

Picture 16 is two bolts you need to remove for step 20

Picture 17 is one of 4 access ports for the A-pillar trim peaces (dat spelling....) use the really small screw driver or your knife to open them, be careful not to scratch the finish

Picture 18 Is the port open

Picture 19 is the central trip panel protecting the air bag connector and the two lower main bolts, pull where you see my hand to undo it. There will be two very obvious 10mm bolts there, undo them. The air bag connector has a red tab on top that you will need to slide over to the drivers side to unlock (might be the passenger side, try both) then it will come out easy

Picture 20 is the power pedal adjustment system panel you need to remove, pull from the top edge and then upward once those clips release to allow the two "claws" at the bottom to let go of the dash. (NOTE, SLT/non-fully optioned trucks can ignore this next step) Then once this panel is loose remove the blue power connector and set the unit in the backseat/bed where you should have put everything you have removed up to this point.

Picture 21 is the pry that I mentioned to use when it's time to remove the shift cable

Picture 22 is the pair of tabs holding the shift cable to the column, push these in after you have the linkage disconnected with the pry

Picture 23 just kinda set the linkage hereish to keep it out of the way

Picture 24 is the passenger side foot well wiring that was covered by the trim, undo ALL of these. They are retained by one tab each that you press down to remove and the antenna connection is one you just pull out (be careful with it if you don't want to kill your signal)

Picture 25 is me showing you the antenna wire with everything now disconnected

Picture 26 is the 3/8 6 incher with 10mm deep equipped on a 3/8 snap-on air ratchet, you need to begin to rapidly dissemble the interior

Picture 27 is where you inset said tool to remove the screws holding down the a pillar trim, do this to all 4 bolts (two each side)

Picture 28 is where you NEED to hold the trim when removing to avoid breaking or deforming it

Picture 29 is the angle you MUST turn the trim to avoid damaging the seal on the dash, remove at this angle and do the same for the passenger side. Move the trim to safety after removal like all the other are keeping them safe and clean aren't you? Oh there is a wiring harness on the driver side you need to unplug too

Picture 30 (God I took a lot of pictures while doing this didn't I......) Is where there was a 10mm screw that you need to remove, it joins the dash to the HVAC unit and is located under the glovebox (not behind, so don't remove it)

Now at this point be sure to bleed off the AC system using a valve stem tool to PARTIALLY unscrew the low pressure side of the AC loop, should be near your accumulator (big tank looking thing). If you try to fully unscrew it it will fly off like a angry hornet and could put an eye out, all you want is a slight hiss.

Picture 31 are two engine bay (yes we are in the engine bay now, remove you air cleaner to have room to work) nuts you need to remove (already removed here) Also undo those two AC quick connects (or just saw-zaw the accumulator off the damn thing because its a TOTAL B****.....I hate quick connects)

Picture 32 is a holder or the heater core hose that you should probably pull off to allow you to move the hose around. lower left corner is the two hoses that you need to use your pliers on to get the clamps off, move the hoes somewhere out of the way and be prepared for coolant to drip. I seriously recommend blowing air with an air-gun into the top heater core pipe to purge coolant out of it so that it doesn't leak into the interior when you remove the HVAC unit

Picture 33 is my ECU, yours might look more....uh.....HEMI like (4 connectors) but in any case unbolt it with an 8mm socket as the screws are too easy to strip, behind it is one nut that you have to undo (10MM)

Picture 34 is taken right next to the shift lock unit that I had you unplug way back, that nut you see is one of four 13mm ones that hold the column to the...uh, big metal thing that attaches to the frame (you get the idea, unbolt the things) there is one on the other side of the shaft and two located closer to the wheel in easy to see locations

Picture 35 is the area around the front two nuts from the last step AFTER you dropped the collum, they are both 10mm and are some of the last bolts holding the dash down. Undo them.......oh and if you did't follow my directions correctly and left something attached to the column it is probably broken now

Picture 36 is what everything SHOULD look like at this point, Notice the front studs that i said are really easy to see that had those two of four 13mm nuts on it? Told ya the front ones are easy to find.......oh and you can clearly see the red tab on the shift interlock on this picture. (NOTICE for any people who have power pedals you MUST press the brake in when lowing the column for the interlock unit to clear the piston the brake pedal is mounted, if you brake (lol, pun) it it's over 100$ to replace and you can't drive the truck with it broke)

Picture 37 is the massive cluster of wires under the parking brake lever that you need to undo, they are all tab retained EXCEPT the massive white center one, it has a 10mm screw in the middle you need to use the MANUAL ratchet to undo

Picture 38 we are back in the bay with me holding my airgun in a bad picture with the heater core hoses disconnected, notice the anti-freeze everywhere and the shiny stage 8 locking bolts keeping my headers quiet.......oh and the nice magnum valve covers! (back on topic)

Picture 39 is a Mercedes S430 who's seats can heat AND cool you AT THE SAME TIME!!!!!!!!!! (okay for real back on topic)

Now I (being stupid) forgot to take pictures of the upper dash so I'm going to go get those now, here ya go

all you need to do is remove the two 10mm bolts and the 4 little black ones I'm pointing at and the dash should be free!

This next picture is the dash removed, BOOM! hard part over! Now start getting that HVAC unit out, there is one screw on the floor near the air bag module and two near the top. This next picture is from another 3rd gen I fixed with the screw locations indicated (shown from front of car)

This last one is not my truck (customers 3rd gen HEMI) but shows where the two studs the fasteners you removed are in relation to everything else, that have green bases

Finally to remove the heater core just remove the foam over the two pipes and then unscrew the two screws over the plate holding the pipes down

Then pull the old core out and slide the new one in, should be a tight fit

Picture 41 is the pinhole leak in my old core

Now all you have to do is the reverse of what you just did to put everything back together, have a partner help with putting the dash back in as its hard to line up the two hooks (they are in between the top two main screws on both ends) alone. Just go backwards through this guide until all the hardware is back together. The shift cable can be put back on its ball by hand, you don't need to use the pry to press it back on.

Now the final steps are as follows, jack up the front of the truck OR park with the nose pointing upward. Next fill up the coolant reservoir to the point it's almost over-full and OPEN the radiator cap (now this should be obvious[not to mention redundant as you should have already had the heater core hoses off] but PLEASE GOD DO NOT OPEN IT IF FOR SOME REASON THE ENGINE IS STILL HOT)

Then you need to reattach your battery (and cry a little knowing your ECU is cleared) and after double checking that EVERYTHING is back and connected the way it should be, start the car.

Let her come up to temp, the rad might bubble and burp and over flow a bit. This is normal and we want this to happen to clear the air out, after the temp is up rev it hard a few times to get the water pump to spin extra fast and try to get any more air out. This is also the point where you need to recharge the AC loop, there should be a label under the hood somewhere showing you how much A123 refrigerant to add. After that is done close your rad cap and make sure you have enough coolant in the reserve tank and then close the hood and go for a drive

Do various things on your left and right turns and acceleration and braking and stuff to make sure everything is happy, oh while doing this BLAST the heat and go through all settings (zones, like face, feet, windshield) and then so the same in cold mode, then mid mode, then do it again to make sure everything is clear and the air is going to the right places at the right temperatures.

Do not be alarmed if bits of foam (dark gery, almost power-like) come though the vents, this is normal as the seals just got disturbed from you working on it. Finally if you have dual zone cooling make sure you can set one side to max heat and the other to max cool and the air does the thing it's supposed to do.

That's it! Congrats! You just did one of the hardest jobs in the automotive repair industry (applause and cheering)

I hope you found this guide useful and if you would like to give feed back PM me and thanks for reading!

Now one last thing......whoever built my truck did not ancour the A-pillar trim screw wells correctly so I could not undo the screw to remove my passinger side A-pillar I had to take a crowbar to it and destroy the trim piece to get the dash out

As you can see there is still a bit of trim under the still stuck bolt, if you guys liked the guide and would be willing to help.....I am accepting donations toward a new A-pillar trim piece, thanks again for reading and stay Mopar my friends!
Magnum Powa!!!

Last edited by striker2237; 05-20-2015 at 11:46 PM.
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Old Today, 06:17 PM
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Thanks for taking the time and extra effort to help
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