MJ Heat problem

[Top C]

My MJ seems to have low heat. I removed the heater hose valve and have flushed the heater. I've measure the heat at inlet and outlet and its slightly cooler at the outlet which I would expect.  Does anyone here have any experience with this? I'm wondering if there is a blockage in the heater box not the heater its self which is not letting good air flow though the heater coils. Does anyone have a real picture of the inside of box housing the air condition unit and heater? The Air conditioner does work and does cool as I would expect. Also I was wondering if there is some kinda of inspection door or someway to see inside the box without taking it apart. I've looked but I didn't see one. 

Thanks

Mike

[eaglescout526]

I have the same issue and I think it just comes with having AC. I used to have really powerful heat but since having AC it kinda lost its power and i don't know why. 

[scguy]

How does your temperature blend door cable feel? It's possible that the foam seals on the blend door are shot with age. What kind of temps are you seeing on your heater hoses? I like to see at least 160 at operating temp.

[Top C]

Yea sounds like you have same problem. I've checked everything except taking the dash apart and I don't want to think about doing that. I was reading different posts about the same problem but all them mostly refer to that Vacuum heater valve on the water line. As said I remove that a while back just because everyone said that will fail eventually. Some did mention in a post about insulation possible blocking the air flow through the heater core. I was wondering if I removed the fan motor if you could see inside the box enough to see if there was something blocking the air flow. I do get good air flow when I move through the different vents along with the defroster. So I don't think that's a problem. I wanted to see if anyone else has something to say here maybe we'll both learn something! The water pump has been replaced and thermostat is new also I forgot to mention that in the earlier post.

Mike

[Top C]

HI SCGuy

Yea I was just posting that someone else mention the form on the door. What does that insulation attach to? If I pull the fan motor out could  I see it that way? Water temps are good going in and like I said earlier slightly less come out which I would expect. 

Mike

[eaglescout526]

I just ran my heat this evening, AC off, heat all the way on both sliders. Got pretty damn warm and with that half a console vent, holy crap that was a fantastic custom mod. Really helped with the heat. 

[Top C]

Eaglescout526

What mod did you do to get all the heat?

[eaglescout526]

Wasn’t really a mod, but more so custom work. What I noticed when using my heat in the winter was that the heat would blow out the bottom floor vents and they wouldn’t really get heat anywhere near you unless you used the vent mode which still didn’t help me a lot. But my half a console with the bench seat has the XJ duct work and lower dash vent and I have the heat coming up and under the console and it felt fantastic. 

[Top C]

Okay thanks for the info on the Mod.  Still wondering about looking inside the HVAC box without pulling the dash apart to see if the insulation might have fallen down and is blocking the heat somehow.

Mike

[eaglescout526]

Entirely possible. I know when I pulled my box the AZ heat took its toll on it and some if not all the foam disintegrated to the touch. I wish I had a more solid answer than just possible causes.  

[scguy]

Do you have good air flow? If you had something completely blocking the heater core you would have poor air flow out of the vents. 

 

I've seen parallel flow heater cores that had flow through but the bottom two-thirds were sludged up, causing very weak heat. I wonder if that's what's happening here. 

[Top C]

So just an update, I flushed the heater core about 4 times and used 15lbs of air with the water to give it a little pressure. Then I filled the heater core with prestone radiator flush and let it sit for 30 mins. Then I re flush it with clear water connected everything back, burp it and now I've got great heat now.

Here is an interesting link about heater cores:

https://heatertreater.net/heater-core