01 XJ Sport w/ 154,000 on her, 4.5" RE lift, 32x11.50's. Flushed radiator, block and heater core twice this summer, new thermostat/upper & lower hose/heater hoses. Blend door motor appears to be functioning correctly, blower fan works great. Jeep runs a needle over 210 on the gauge at 75mph when it's 105deg outside.

Problem: Heat is luke warm most the time. Noticed last night that when rpm's go up to around 3grand the heat gets noticeably better, almost acceptable.

Could a bad/worn water pump cause this? My gut tells me no since this jeep doesn't get hot and we all know how sensitive they are to the cooling system? Thoughts?

 

Re-flush your heater core in both directions several more times. I bet after you do that you will get more heat.

 

x2

 

Alright, flushed heater core back and forth this even 4 times. Even let it soak with CLR in it for almost an hour. Water runs through it clean.

Got her topped back off and purged and there is no changes. At idle-1500 rpm it's warm but not what I would expect. Take it to 3000 RPM's and the air gets HOT. I also noticed that the upper hose doesn't get real firm at temperature.

Should I pull the water pump next?

 

i know nissans are sensetive with air pockets..idk about xjs..have you tried burping it.it dies have a t-stat right?mine didnt have one when i bought it..my heat worked better after i put one in

 

Since back flushing the heater core didn't help I would start looking into the water pump and t-stat. I know you said you changed out the t-stat but I know that many have had a lot of problems with after market ones and suggest getting an OEM one from the dealer and it should be a 195degs. BTW, you shouldn't really have to worry about air pockets on the later models of XJ's as long as you run it until it reaches normal operating temp with the rad cap off.

 

Hey I know this thread is kinda dead, but I was wondering if you found a solution. I'm in the same boat and I even replaced my core. The only thing that is not new in the system is the pump and the rad cap.

 

No change. I am beginning to think the air passages are clogged up. Will be ripping dash out this spring to see.

 

Yea when I pulled mine apart it had all sorts of crap in there. But there is a mesh filter on the incoming side of the evap core and it all gets stopped up right there. Maybe you could try one of those lint lizard things from walmart and go through the recirc door. Or pull the blower motor and vacuum it from there. If I remember right with the blower motor out, you can reach in and touch the evap core. (All air passes through the evap core first.)

 

I have found the mesh **** coming out my vents. My fans blows hard but not much air coming out, nothing like my buddies.

 

Using a laser temp gun, measure and compare the temperatures of the upper and lower hoses going in/out of the heater core. They readings should be very close. Mine read right around 175 with the engine at operating temperature.