So I picked up a 2wd 96 XJ recently with what I thought and was told initially a bad head gasket. Turned out to be a cracked head, but no biggie so I picked up a rebuild off of ebay. The new head is actually a 7120.

Long story short i've put a new water pump on it and a new radiator, and put in a new t-stat with the head.

The thing will not run cool, the heat is working great so I don't think I have a air bubble in the head, i've parked in on various inclines to help work any air out of the head but I still can't get coolant flowing through the radiator.

The upper radiator hose eventually gets pretty hot but there doesn't seem to be any real pressure in it and the lower hose is never really getting hot. I think any heat in there is just from some coolant squeaking by, the lower potion of the radiator is also not getting warm at all.

The t-state was new but i'm pretty much suspecting it at this point, I didn't test it prior to installing it which might have been a bad move.

What is ya'lls opinion? I was really hoping not to crack the system again since i'm sick and tired of working on the thing by now, but it sounds like it must be done, lol.

The heater core was actually just about able to maintain temperature while idling tonight since it was 50F or so ambient, so I was able to let it run a good long while and it never got better.

 

I'm new to the xj but not new to turning wrenches so I'll help you the best I can.

How the fan clutch?
Is it real easy to spin? Or is it resistant to being spun?
Does your electric fan cut on?
Have you put a temp gun on different areas to see just how hot it's getting?
I've heard talk of water pumps that are ment to turn the oposite direction than what our xjs take. Not sure if you could have gotten one or not.
Could also be a blockage in the system did you flush it?
Any pressure building in the coolant system?

 

Fan clutch is new also, the old one was likely the original and had 161k miles on it, it was toast.

The electric fan doesn't cut on but i'm not sure i'm letting it get hot enough or not, I can physically feel the bottom part of the radiator not even getting warm, or the bottom hose. I don't have a temp gun, so haven't done that. The pump is obviously circulating coolant just fine for the heater core, but the pump I put on was the same as what came off and had a R on the impeller which I believe to mean reverse.

I think at this point i'm just going to open the system again and remove the t-stat and make sure it stays cool then. When I had the head off there was some buildup where the head gasket partially covers some of the coolant passages but I didn't see anything enough to cause a blockage at all.

 

Don't be suprised if what your not seeing has settled in the radiator and blocked it off. Sounds like you've got a good idea of what to do. Is your xj obd2? You can use a scanner to see what the computer sees for a temp. Don't trust the "gauge" on the dash

 

Problem solved, or well not technically solved. I took the thermostat out and it's running so cool the heat won't work not which was expected.

This one is OBD II, good point on looking at that temperature, the sensor in the head was replaced twice actually so I would hope it's fairly accurate. I managed to break 2 of them lol. I do have a new one laying around for the computer sensor also though just in case. It's not throwing a check engine light so I assume the one the ECU uses is working.

Thanks for the replies but sounds like my culprit was a new t-stat that won't open. It also doesn't have bleeder holes so i'm going to get one that does now.

 

Well, testing the thermostat proves it's good but it doesn't have a bleeder hole so i'll probably add one or pickup one with a bleeder. Since it never even gets hot without a thermostat it's likely air trapped around the thermostat i'm guessing.

 

Turns out part of my problem is the sender or the gauge in the dash is reading something about 30 degrees too hot. This made me think it was running hot when it wasn't really.

I will say adding the 1/8" hole into the thermostat flange made a big difference in getting the air out of the head though and save me from unbolting the valve cover to get a socket on the temperature sender.

Today I put my OBDII reader on the port and watched the coolant temp reported by the ECU and it was nice and steady at 195-197 even idling for 20 minutes or so with the hood down while I filled up all the tires.

Going to do an oil change and call it good, no codes or anything from the ECU.

Does anybody know if there is a way to test whether the ECU will flip the electric fan on if the temp gets too warm? It was almost 70 today and the mechanical fan kept it cool but a little peace of mind that it will turn the fan on would be nice.

 

Good luck getting the ECU to turn on the electric fan. It is the mysterious unicorn to me.

I have only seen it go on when it was 90 plus degrees outside, humid, stuck in traffic, temp gauge beginning to touch the red block on the high end of the gauge.

If you search this forum, you will find many users asking the same question. The FSM says it should kick on at 218 degrees, so either the gauge is off, the ECU is off, or the FSM is wrong. I think the FSM is wrong here and the temp it kicks on at is much higher.

 

Well, I have a brand new sender in mine and the gauge is reading probably 220-230 but the ECU see's 197 from the thermostat housing. So it's certainly possible the gauge is reading wrong.

I'd really like to get a reliable temp readout on the dash, but it's sounding like my only option might be a aftermarket mechanical gauge to get that, lol.

The temp reading from the sensor in the t stat housing seems quite accurate though, it was showing me 197 and I have a 195 thermostat in there, but I don't want to always have my phone connected to the OBD. Also it doesn't help if you have a 95 or older.

 

My gauge reads way too hot also I blame it on the cheap auto zone parts I do have some temp creep at idle though and plan to replace the water pump and fan clutch. To check my electric fan I just unplug the computer temp sender and it will kick on it'll throw a code but it does come on. Also I have verified if my sender for the computer sees 218 the fan does come on

 

Cool. I would just do the fan clutch first and see, I replaced my water pump also since I saw some brown sludge/rust in the system but the impeller was still 100% perfect.

The temp creep I would bet is the fan clutch, mine had 161k miles and 20 years and it was beyond toast. It moved pretty much no air and you could have grabbed it with your hand. The new one is a huge difference air movement wise.

 

Oh yeah fan clutch will be first for sure

 

For peace of mind,I would replace the ecu temp sensor in the thermostat housing with a mopar unit also.

 

Well got my temp creep fixed old fan clutch was well beyond shot. Took it off turned it in my hand a few times and it went completely loose no tension at all felt like a wheel bearing lol. I would just verify what the computer is reading with a infrared temp gun on the housing. That's what I did and computer was seeing just a few degrees cooler than what the temp gun said so I know mine is good