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Heater Core Questions


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I've noticed over the last few months that there has been a slight loss of coolant. I pulled back the carpet on the passenger side, and noticed the insulation under the carpet is damp. I'm concluding that the heater core is leaking. Here's my questions.1. If I wait until late summer or fall to repair this, and if I don't use the heater, will it continue to leak into the cab?2. I'm thinking this is a job that is too big for me. What should I expect to pay to have this fixed?Thanks to all who respond,Eric

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#1 yes it will continue to leak. #2 If you are somewhat mechanically inclined it is not difficult to do. I just redid my dash and rebuilt the hvac box 2 or 3 months ago. this is a good read on the procedurehttp://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/27-hvac-heating-ventalation-and-air-conditioning/57-air-conditioning-evaporator-core-heater-core-replacement. I had never removed a dash before. I did it taking my time over a weekend. I also replaced my cracked dash at the same time. about 3 years ago I had an ac man tell me it would cost near $900 to do this. It really is alot easier than you think.

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Heater core replacements are pretty easy really. Dodge was fairly smart with the modular dash design. So this allow the owner to move or remove the dash as a unit with little to do as in disconnecting wire and devices. But once you swing the dash as side on the passenger side then the HVAC box is very visible and very easy to handle.

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I think you can get some hose and run the heater line in a loop and take the heater core out of the equation. As for the dash, I think its a PITA, I wouldn't do it again. I don't know how Mike has such an easy time but I thought it sucked. Then again he didn't pull the entire dash out so maybe that's easy. Just follow his instructions if you do it, if you are lost CALL HIM! I wouldn't do any guessing with that dash as its all plastic and pulling on it with a screw you missed could mean just breaking the screw hole out.

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I noticed that the rubber mat under the carpet was not wet. So I pulled it up. Wow, the under side of the rubber mat is soaked! I guess that means the leak is closer to the firewall. Does that change anything in my conclusion that the heater core is leaking and that's where my coolant has been going?thanks again!

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Could be a bunch of things going on. The coolant is leaking out of the heater core and running out the A/C drain and dribbling down the firewall back into the cab. Could be the A/C just draining back in and the coolant is leaking else where. But I'm going to bet it the heater core yet and just draining in the cab and you just can't see it from the driver view...

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I think you can get some hose and run the heater line in a loop and take the heater core out of the equation.

As for the dash, I think its a PITA, I wouldn't do it again. I don't know how Mike has such an easy time but I thought it sucked. Then again he didn't pull the entire dash out so maybe that's easy. Just follow his instructions if you do it, if you are lost CALL HIM! I wouldn't do any guessing with that dash as its all plastic and pulling on it with a screw you missed could mean just breaking the screw hole out.

I read Mike's article before I did mine and had no trouble. I think the key to it as you mention is just taking the one side loose and not trying to completely remove the dash. That would seem to me to be much more involved.

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I think you can get some hose and run the heater line in a loop and take the heater core out of the equation.

As for the dash, I think its a PITA, I wouldn't do it again. I don't know how Mike has such an easy time but I thought it sucked. Then again he didn't pull the entire dash out so maybe that's easy. Just follow his instructions if you do it, if you are lost CALL HIM! I wouldn't do any guessing with that dash as its all plastic and pulling on it with a screw you missed could mean just breaking the screw hole out.

I read Mike's article before I did mine and had no trouble. I think the key to it as you mention is just taking the one side loose and not trying to completely remove the dash. That would seem to me to be much more involved.
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Alright, you guys have talked me into it. Some of you walked me through installing my rv275's last year, so I may lean on you a bit on this one too. One last question, is there anything else I should do while doing this heater core replacement?

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I second the evaporator. I also replaced the connector on the blend door. It is a small plastic piece that connects the door to the motor that turns it. Google "heater treater" and you can see it. Mine was cracked and affecting the heater. It can be replaced without removing the hvac box, but is very easy with the box on a bench. I also replaced alot of foam gaskets while I had mine out. Just depends on what yours looks like when you take it out. Be careful when you pull the box out, I broke off a couple of the studs when removing mine. You have pull the box out and down at the same time. A couple of the studs are vertical and the rest are horizontal. You should see that when you remove the nuts.

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For the last couple of days, I've ran the AC. It is not draining. I put a vac on the drain, and still nothing. However, I've also had the carpet and rubber mat pulled back to dry, and during that time I've not seen any water in the floor board. I ran my car's AC for a while and it produced condensation drainage, so I know the humidity level is sufficient to produce significant condensation. None of this is making sense to me. Am I missing something?

Could be a bunch of things going on. The coolant is leaking out of the heater core and running out the A/C drain and dribbling down the firewall back into the cab. Could be the A/C just draining back in and the coolant is leaking else where. But I'm going to bet it the heater core yet and just draining in the cab and you just can't see it from the driver view...

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When I opened my hvac box up there was all kinds of crud in the bottom of it. I suppose there was enough to allow any liquid to build up without getting to the drain and then leaking when it finds a place to leak out. I cant say thats what is happening but I could see it as a possibility.

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  • 3 weeks later...

It took me all of three hours to do mine, it's very simple once you understand how the dash comes down. Be careful and don't rush or tug. I cracked my dash in two spots because I got a little impatient. Take your time and focus, you'll be fine. As with every project, pictures and notes along the way help.Definitely, as already stated, change your evaporator while in there. I also changed my blower motor, not a must but it was out so it got done.

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