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Luke warm heat


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I have had catastrophic failures of HCVs. Likely one of the reasons for my hate of them.

When they split apart driving down the road, MASSIVE coolant loss that could lead to engine damage. Not worth it....

 

Here's my favorite. Gonna do an oil change on my wife's xJ. Good and warm!! 

as I'm removing the oil filter, my arm touches the heater hose or HCV and it explodes!! Covers my left arm and my face with 208* coolant!!

That's with a factory valve. I'm sure the available replacement valves are worse.....

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2 minutes ago, cruiser54 said:

Here's my favorite. Gonna do an oil change on my wife's xJ. Good and warm!! 

as I'm removing the oil filter, my arm touches the heater hose or HCV and it explodes!! Covers my left arm and my face with 208* coolant!!

That's with a factory valve. I'm sure the available replacement valves are worse.....

That makes a believer out of me.  I had the mechanic replace the HCV even though it was not malfunctioning but probably original.   I asked him about A Mopar one and he said that some of those made later might be better.  

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17 minutes ago, Minuit said:

 

 

I went through the FSM quickly to see if I could find an acceptable spec for vent temperatures and came up short, but if there was a spec I would expect 140 to be within that spec, especially on a very cold day. In my mind, 140 is roughly where "good heat" starts, and I personally wouldn't call 140 "lukewarm" either, so there may very well be something else going on here. Like I said, it'd be best if you could collect your own measurements of the vent temps and report back.

 

Maybe I have less of an issue that I thought. Less heat than in most cars though

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On 12/9/2020 at 7:20 AM, cruiser54 said:

I can't imagine the heater core is that dirty and it would happen that fast. 

Hold your hand on each of the heater hoses at the firewall. Same temp?

either side of the HCV. How do they compare?

 

If you have an IR gun, use that. But, your hands will likely tell the story. 

The intake and discharge hoses at the firewall feel to be about the same temperature.  The hoses on each side of the HCV feel to be about the same temperature also.

 

I ran across this picture.  I guess an AZ plumber had some left over copper.

 

88 jeep cherokee HEATER HOSE LINES - Jeep Cherokee Forum

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I spoke with the mechanic who has done all the work on my 2 MJs.   He said he checked the blend doors and found them to be ok.  He said one of the hoses going to the heater core was very hot and the other was not. (A change from what I had stated.) He also said that even though the new heater core was installed only a year and half ago, the flushing of the radiator and engine was very rusty. He spoke of working on an XJ recently with a heater core he had installed about 5 years earlier and was filled with rust.  I will take the truck back Tuesday for him to disconnect hoses and flush the core.  I also asked him after he flushes it to attached short pieces of heater hose to the heater core and turn them up and fill the core with a rust dissolvent and leave it for a day and flush it again. 

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