Very little heat- Diagnosing the source of the problem?

JeepJeepster

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If I was truly needing to flush a cooling system, I would buy some prestone or zerex cooling system flush. Drain the system completely, including taking the block drains out. Fill it back up with distilled water and the cooling system flush, drive it a bit, then drain and refill with distilled water till clear. Drain and refill with 50/50 G05.

The key is removing the block drains so the system is truly empty each time.

I cant remember how much I put back in my 04 KJ after replacing the hoses/stat, but I recently did an 06 WK hemi that is suppose to hold 14.5qts. I didnt remove the block drains and probably should have as it was a bit overdue for a coolant drain/fill, but I only put 8qts back in it. That engine is so tightly packed in there its hard to get to anything... I'll most likely just drain and refill again in a year or so.
 
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WheelNut

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I notched the fan shroud yesterday and it came out nice and easy. Who knows why Jeep didnt design that notch into the part. I guess its a safety thing? That way its harder to run the vehicle with no fan shroud.

Thanks for the run down on flushing Duster. That helps me wrap my brain around the task.

I’ll be picking up a few more things at the ol’ parts store today: Coolant system cleaner, more distilled water, upper and lower rad hoses, and an easy out to get the dang bleed screw out. Hoping to get some good flushing done this weekend.

Jeepster: Do you know how to access the block drains? The FSM shows them as below the exhaust manifolds. I tried to spy them yesterday, but I couldn’t see or feel them down there.

I was thinking I’d try putting some pressure into the system with the lower rad hose off by removing the bleed plug and putting an air nozzle into that hose to blow the rest of the coolant out. I’ll set the pressure low- about 15psi to match the standard system pressure. Any idea if this might drain the block?
 
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JeepJeepster

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Probably doesnt pull as much air when you notch the shroud... Allows air to be pulled in the bottom of the shroud instead of through the radiator.

I'll take a peak at mine and see how best to get to the drains.

With the air idea, you would need to close off the upper hose or just hold your hand over it once you take the hose off. Cant hurt to try if you use low pressure like that.
 

WheelNut

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On Saturday I drained as much as I could from the cooling system (about 2 gallons/8L) and refilled with Prestone cooling system "flush+cleaner" and distilled water. Installed a new thermostat, new accessory belt, new tensioner, new upper rad hose, and I tried to install a new lower rad hose, but the parts store gave me the wrong hose so it wouldn't fit. I decided to take the Jeep to the dealer to have them do a coolant flush in the hopes that would get ALL 14L of coolant out of the system and fill the whole thing up with HOAT. So, I took it in today and spent the $250 to have that done. They filled me up with Mopar VU01524AC, which is supposedly a HOAT coolant and the VU number is just a non-US P/N. I don't know what the US equivalent would be though. The Mopar Chemicals List website shows VU01524AB, and I would assume that VU01524AC is just the latest update to that same thing.

Anyway, the heater is still as weak as ever, of course :(. The lines in and out of the heater core are both super hot, and maybe one is cooler than the other. Hopefully I can find my IR temp gauge to check it soon.

I might try flushing the heater core one more time, but I'm pretty sure I just need to bite the bullet and pull the damn dash out and replace HVAC parts. Not exactly sure what to pull as there are seemingly multiple issues. I can't select defrost, so there is probably something wrong with the vacuum system in there, and who knows, maybe there is a blend door issue that is stopping me from getting 100% hot air flow. If I do take the dash out I'll probably change as much HVAC stuff as possible as I only want to have to go through that headache once.
 

tommudd

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The issues with the heater core is that if it is plugged any at all antifreeze will just go in and back out bypassing most of the heater core
 

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