So I just bought this 05 ram 1500 last week, it's great. I love it. But my heater doesnt work. So tonight I decide to do a heater core flush. I pop out the air filter for easier access and I find the core lines disconnected from the pump, and a bypass installed. Why? I assume the previous owner/or the dealership is too lazy to try flushing the core. So I flush the core. I put clean water in, nothing but clean water out.both directions since I still don't know which is input and which is output. No debris or anything.
now I'm draining coolant since I no longer have a high point to use, and I need to remove the bypass from the pump to hook it back up.
my problem is wondering why this was done in the first place. Maybe the astute among you can think of a reason why someone would bypass a perfectly clean heater core?
Pump bypass of heater core on 05 Ram 1500

UPDATE: So turns out there was a reason, heater core is leaking like a submarine with a screen door. After putting it back together I discovered a soaking wet carpet in the cab of my truck. Over the next couple days I will pull the dash apart and remove the core and attempt to braze or otherwise seal the leak, if I can't do that I will obviously buy a new one. In the mean time I am going to reinstall the bypass since without it my coolant temp spikes like 1 stroke.

 

You will be better off in the long run to buy a new core. You have to pull the dash to replace. If you miss a spot of the old core during your repair. Do you really want to pull the dash again.

 

Most likely since you did not pressurize the heater core just flushed water through it, it most likely have a leak in the core and dash will have to be removed. I would hook the hoses back up asap and check for leaks inside the cabin passenger side. When you do this put the defroster on and see if the windshield will fog up. Also some people disconnect the hoses so they will get colder air conditioning air through the truck if the AC is not throwing cold air.

I bought a car 1964 Pontiac Grand Prix with a factory Hurst 4 speed on the floor years ago when I was a kid and same thing hoses were disconnected cool weather came tried the heat and no heat. Guess what hoses were disconnected, guess why they were connected heater core had a leak. But back then the heater core on cars came out the engine bay easy fix. If yours is leaking get it back to the dealer as this is a cheap part but labor about $1k from the dealer.

Good luck

 

So should I have filled the core with coolant before hooking it up? What I did was flush it with water both ways, and then blew the water out with air and hooked it up empty. I'm in the process of taking it out now. I plan to aluminum weld any cracks I find or replace it.

EDIT: The truck was in Phoenix the first 9 years ( I'm in El Paso), so the idea of bypassing it for better AC is completely feasible, I may have busted it trying to get it to work. I'm the third owner after the dealer. But in my process of taking the dash out now and there are signs it has been done before.

 

I would of hooked up the hoses and got the truck to operating temp and check for leaks on the passenger side. If no leaks previous owner might of disconnected it for better ac cooling but if your gonna remove dash and replace the heater core that will ensure no leaks. You will also have to remove the ac lines, evacuate the freon so be careful. Do not repair the core buy a new one they are cheap.

 

I had to do this on the road when my heater core took a **** and dumped coolant all over the passenger floor. My guess it's either this or it's plugged and the person didn't want to go through the hassle of removing the dash (or paying someone else to do it).

 

Learning experience
so despite not having a new core yet I decided to just get a look and feel for the work and find the problem. This is the output of the heater core. Turns out it can't handle the pressure from the pump no more, the core itself works just fine. Spent last night and this afternoon pulling the dash out to see this, but now I'm confident in myself doing this job when I get the new core, I won't have any problems doing this again. I imagine all the time this wasn't hooked up maybe the seal internally rotted away. next time I'll have to make sure I have the proper equipment to discharge the freon to take this box completely out, didn't do that this time. There is a way to open it without doing that but it is destructive to the box itself and I don't want to do that.