We got a 95 Grand Cherokee with a 318 (5.9?). With the radiator Almost completely blocked off the engine temp is around 150 and the cabin temps are pretty low also. Outside air is in the 40s. I have replaced the Superstat from advance Auto that was less then 6 months old with a dealer one (26$ compared to 7$) With no change. I did the pan on stove test with the superstat and it worked OK. I have also Burped the system the best I can but I think that would just cause overheating not under heating.
I have replaced the fan clutch thinking maybe it was locked up and spinning too much. (Another $70 wasted) Radiator cap also. Heater core has been flushed. Radiator and water pump less then 5 or 6 years old.
I know that there has been some air blend door issues with these, And I do have the issue of it being kinda broke. BUT i am 100% sure the door is all the way open to the heat side. that's another long story.
So right now I'm thinking low engine temps = low cabin temps= cold wife.

We have been dealing with this problem for a couple of winters now and its getting old being cold.
Please help, Thank you

 

5.2=318 5.9=360 im dealing with a similar issue it sucks. air in the system would cause something similar to what you are dealing with. but then again im having the same problem and cannot get any more air to bleed out and still no heat and the temp gauge barely gets to op temp. good luck update when you do figure it out so others can learn!

 

I have installed a auxiliary homemade bleeder in the heater hose at the highest point to fix one I had to that before. I thought all the air was out and it wasn't even close.

 

I see the "T" you put in in your pics. I am having similar trouble w mine. What method for bleeding that air out did you use???? Im desperate to get my rig running at OP temp. Thanks

 

I have a funnel I jam in the neck of the rad. Careful, its plastic. Then fill it till the funnel get about 3/4 full. Start it. You need a tight seal at The funnel/rad neck. The point of this is as air burps out coolant goes in, so keep the funnel full enough that it always will suck in coolant and not air. I do this for a few min varying the rpm's maybe up to any 2200. Squeezing all hoses while doing this helps get air out. Cycle heat to ALL settings including off. I shut the engine off with the funnel still.in and let it cool a lil bit, when it cools it will suck in more coolant. Thats how The overflow works. then I suck out The extr
a coolant from the funnel with a suction gun. Then put on your cap. Warm the engine and then crack loose your bleeder and let it run untill you get NO air at all. Don't let out too much coolant without checking the rad. About 1/4 cup at a time max. You don't want to have to.start over. I always use this method and it has never let me down! Sorry if there are a few mis spellings, my phone auto correct sometimes when I done want it to! Lol

 

So you think its just air in the line then?

 

EXCELLENT step by step! thanks man! I am doing this this weekend for certain! Thanks!

 

Not sure if its just air, but a pocket of air trapped in the heater core sure does make lousey heat. The quickest/easiest t to use for the auxiliary bleeder comes in a cheap radiator flush kit at auto zone. The stant brand ones seem to be pretty sturdy.

 

nice, thats exactly what i was thinking I was going to use when i saw your T in the pic. Tomorrow is weekly "workin on the XJ's" time, so ill let you know how it goes. everything in my cooling system is less then a yr old (dont know the age of the heater core though), so if this doesnt do it ill be flushing the core, then totally out of ideas.

 

OP. Have you verified that your temp really isn't getting that hot? Temperature senders do go bad.

 

I have a 318 in my Dodge truck. A trick to bleed air is to drill a small hole say 1/8 inch in the Therm stat before you install it. It allows the air through without affecting how the stat works.

 

T-stats do not seal air tight. Some have a bleeder hole in the flange/seat, most others have a bleeder notch in the valve itself.

 

Yes and very important that you put that hole in the vertical position when you install in the head! But not all therms have the blow by hole.