Heater core coolant amount?

I'm in the process of doing the dreaded blend doors on my 02 Overland and Im thinking about replacing the heater core while I have the whole dash and hvac assembly apart. I haven't drained the coolant yet and I have the dash out already. Haven't taken out the heater box assembly yet so I was wondering if I should drain the coolant first before removing the heater box or just tape off the hoses and just replace the core? How much coolant will I need to refill if I don't drain the coolant and just replace the core? Another question is about the heater hoses. Someone was saying that it would be hard to get a good seal when putting the old hoses back onto the new core. That true or is it possible to reuse? I don't see why it would be a problem since they are clamped on. Some insight on these issues would be greatly appreciated, Thanks.

I'm in the process of doing the dreaded blend doors on my 02 Overland and Im thinking about replacing the heater core while I have the whole dash and hvac assembly apart. I haven't drained the coolant yet and I have the dash out already. Haven't taken out the heater box assembly yet so I was wondering if I should drain the coolant first before removing the heater box or just tape off the hoses and just replace the core?


Tape off the hoses (or mate them together with a short piece of pipe and clamps). If it's nearly time to replace your coolant anyway, then a drain could be the easier option.

...Another question is about the heater hoses. Someone was saying that it would be hard to get a good seal when putting the old hoses back onto the new core. That true or is it possible to reuse? I don't see why it would be a problem since they are clamped on. Some insight on these issues would be greatly appreciated, Thanks.

You should be fine; I've replaced more than one heater core and not had an issue; you might see a little leakage at first if the clamps aren't tight or if the hoses are no longer supple....but if the hoses have become non-supple then it's time for replacement anyway.

[QUOTE=fredjacksonsan;7011824]Tape off the hoses (or mate them together with a short piece of pipe and clamps). If it's nearly time to replace your coolant anyway, then a drain could be the easier option.


Thanks for the insight. I did manage to remove the hoses and put a plastic 3/8" plug on them. It looks like I can reuse the hoses without any issue. Once I got to the core, it looks like its developing a slow leak b/c I can see calcium deposits on the outer lower corner and some on the bottom of the housing. I will definitely be replacing the core. In regards to the coolant, I will be changing it once I put everything back together. Should I drain the coolant now with the core out? I take it that I should be able to completely drain it out through the rad?

Yeah; just disconnect the lower radiator hose and unstop the heater hoses and it should all run out pretty quick.

You might have to burp the system quite a bit when it's all back together, but you knew that.
:)

Yeah; just disconnect the lower radiator hose and unstop the heater hoses and it should all run out pretty quick.

You might have to burp the system quite a bit when it's all back together, but you knew that.
:)

Thanks for the info Fred. I didn't think about the burping part....lol. Yah I will bleed the system when i put the new fluid back in. Thanks again for the reminder. Just ordered my parts from a dealership in Pennsylvania, so much cheaper than Canada. :grinyes:


Regards,

Rob

Yeah; just disconnect the lower radiator hose and unstop the heater hoses and it should all run out pretty quick.

You might have to burp the system quite a bit when it's all back together, but you knew that.
:)

I drained the system through the petcock and drain valve but I only got about half of the coolant out. The drain valve method is slow to drain cause of the small opening. I even disconnected the lower rad hose thinking theres more fluid trapped but nothing came out. I also unplugged the heater hoses and not much more came out. I guess the other half is in the engine still. I don't really want to unplug the drain valves on the block to drain the rest. I have the heater core and the HVAC housing unit already installed but the dash has yet to be installed. The coolant didn't look dirty at all. What's the best way to get the rest of the old coolant out without unplugging the drain at the engine block?

Can I fill the system up with distilled water, run engine to op temp, cool then drain and repeat till water runs clear? Then fill the rad with pure mopar antifreeze which will mix with the water thats in the engine and make it roughly a 50/50 mixture? Top off the overflow tank with 50/50 mix and call it? Any suggestions? Thanks.