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Unread 10-01-2012, 05:41 PM   #16
djb383
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1998 XJ Cherokee 
 
Join Date: Jan 2010
Location: The Republic of TEXAS
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If the belt rotates the pump counter-clockwise, it should have a "R" stamped on the impeller.

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Unread 10-02-2012, 11:58 PM   #17
Reptile
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1991 XJ Cherokee 
 
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This sounds way too familiar... thermostat bad out of the box, yep been there. Let me guess, it says Motorad on it? If you hear the thermostat open, doesn't mean it's opening all the way. The only way to rule out the stat is to take it out and see if you're still overheating.

You need to figure out if it's overheating in the first place. How do you know the engine is hot??? I mean I could tell you if a chick is hot, but an engine? no clue... Keep in mind that what your gauge is telling you could be wrong... Your 96 should have a temperature sending unit (I'm not talking about the coolant temp sensor). Test it with a meter against know temperatures. Boiling water has a constant temperature of 212, you should get a corresponding value in the vicinity of what's in the table. Hopefully these values apply to your model of sensor...

Temp Ohm
100 F (38 C) ...................................... 1365.0
220 F (104 C) ....................................... 93.5
260 F (127 C) ....................................... 55.1

Now you know the sensor works, assuming it does... do a reading while it's on the engine, that way you're reading the temperature off of the sensor and not the gauge (which could also be faulty).

While you're at it, test the coolant temp sensor. Since you've bypassed the e-fan, I can already tell you it's bad...

Temperature F ( C) Minimum Ohms Maximum Ohms
-40 (-40) .............. 291,490 .......... 381,710
-4 (-20) ............... 85,850 ........... 108,390
14 (-10) ............... 49,250 ............ 61,430
32 (0) ................. 29,330 ............ 35,990
50 (10) ................ 17,990 ............ 21,810
68 (20) ................ 11,370 ............ 13,610
77 (25) ................. 9120 ............. 10,880
86 (30) ................. 7370 ............... 8750
104 (40) ................ 4900 ............... 5750
122 (50) ................ 3330 ............... 3880
140 (60) ................ 2310 ............... 2670
158 (70) ................ 1630 ............... 1870
176 (80) ................ 1170 ............... 1340
194 (90) ................. 860 ................ 970
212 (100) ................ 640 ................ 720
230 (110) ................ 480 ................ 540
248 (120) ................ 370 ................ 410

By the way a friend who's overheating your Jeep is not a friend, he's dead meat.
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Unread 10-03-2012, 12:26 AM   #18
GetLifted
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I like this dude^
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Unread 10-03-2012, 04:17 PM   #19
BlackPearl
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This sounds brilliant. Since I just discovered there's a leak by my water pump I'm pulling it this weekend to fix that, check for the "R" on the impeller blades, and pull the t-stat to run the engine without it to see how it runs.

And now where would I find the temperature sending unit so that I can test the Ohms on it, is it on the t-stat housing?

Thanks for your help, it's greatly appreciated!!
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Unread 10-03-2012, 06:53 PM   #20
Reptile
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1991 XJ Cherokee 
 
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The sensor on the stat housing is your coolant sensor. The sending unit is at the very back of your engine, driver side, right next to the valve cover (not far from the ground strap stud). Unlike the coolant temp sensor, the sending unit doesn't have a two prong connector so it's a little inconvenient to probe. To measure the impedance, you probe the tip of the sensor against the sensor's ground (the thread of the sensor)... They got rid of the sending unit on the late 90's models, but I'm pretty sure yours still has it.
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Unread 10-03-2012, 09:42 PM   #21
djb383
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Quote:
Originally Posted by BlackPearl View Post
......and pull the t-stat to run the engine without it to see how it runs.......
......or u can test the stat in a pot of water on top of the stove using a cooking thermometer. Doing this will eliminate one off/on install of the stat cover. Do not drop the stat into a pot of boiling water.......that's not the way the stat is exposed to coolant (sudden boiling) when installed the motor.

180 rated t-stat closed at 180 and fully open at 195.
016.jpg   014.jpg  
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Unread 10-03-2012, 10:26 PM   #22
filluptrk
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You have the same temp sensor my 00 has, on the thermostat housing, not on back of engine. I found that the most accurate one I have used was from NAPA/EICHLIN.
I am not aware of any XJ pumps in your year that are not reverse rotation.
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Unread 10-03-2012, 10:50 PM   #23
BlackPearl
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Wow you guys have posted some great info so far thanks. I'll check the temp sending unit tomorrow, I have time tomorrow afternoon. And it is at the back of my cylinder head and I know this because I broke my previous one when I changed my cylinder head haha Let's hope it's not another broken part right out of the box.

I'll keep you guys updated as to what's going on. Thanks again.
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Unread 10-03-2012, 11:19 PM   #24
Reptile
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So this has been going on since you replaced this sensor? This right here tells me there is a possibility you might have gotten the wrong sensor. When I looked for a replacement, I found out that sensors that would fit on my engine (meaning matching thread) had different calibrations/impedance. See, the problem is the sensor must be specifically calibrated to the gauge. Otherwise, the gauge reading is going to be skewed. Since I didn't know what my original sensor's impedance was supposed to be, I ended up changing the sensor + matching gauge assembly... the whole thing.

Unless you go to the dealer and get the matching part # off of your VIN# (you know how dealers work...), finding the right sending unit is going to be a challenge. Another option is to go pull one from the junk yard, preferrably from the same year model as yours.
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Unread 10-03-2012, 11:28 PM   #25
BlackPearl
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There's a Jeep AMC salvage yard not far from me. I could probably give them a call and see if they have something for me.

The Jeep has always been running a bit hot, but in Phoenix in the middle of summer I expect it would. So now I'm beginning to think you may be right about the sensor. I had no idea about the sensor calibrations. Anyways I still need to put a new gasket on my water pump so that's coming out and I'll be in there so I might as well take out the t-stat to just double check.
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Unread 10-03-2012, 11:33 PM   #26
filluptrk
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What you say is interesting. When I checked Rock Auto the part for his 96 and my 00 look identical, and they don't show any other sender. I do know different parts show different temps on gauge. My NAPA part is right on the money, the other one worked but it always differed a lot from my infrared reader, at least at the gauge.
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Unread 10-04-2012, 09:08 AM   #27
Pats94
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Make sure there is a spring in the lower hose.
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Unread 10-04-2012, 10:48 AM   #28
filluptrk
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Pats 94 is right, they are not always in the replacement. Fortunately in my case the one in the old hose was good, but you can get some 1/16 stainless wire and make your own if none inside the hose.
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Unread 10-04-2012, 11:42 AM   #29
djb383
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'96 down factory gauge uses a sending unit that is located in the back of the head/drivers side (as mentioned) and that sending unit controls where the gauge needle points. From what I have read, there are 2 sending units......1 for instrument panels that have gauges and 1 for the idiot light instrument panel. '97 up XJs have a coolant temp sensor ONLY, and it's in the t-stat cover. The ECU controls where all gauge needles point on '97 up XJs.

If a replacement bottom hose comes without a spring inside, then the spring is not needed in the new replacement hose. It's a pressurized cooling system and internal pressure keeps the hoses from collapsing.
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Unread 10-04-2012, 03:57 PM   #30
BlackPearl
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So I'm going to guess that the gauage I have is wrong. I just ran my 1996 XJ and the temp gauge on the dash was up to the 3/4 line right before redline, which I'm guessing is right around 235 or so and my multimeter was saying 121ohms from the actual engine block...I haven't used a thermal sensor yet, but that's with the multimeter.
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