Running too cold

Speedo flaky - doubt it's the same thing. if it's the MJ (I honestly forget which this thread is about now) then the speedo is mechanical drive, if it's the XJ check to see if the wiring harness is hanging on the exhaust. Mine did that, wore through, and the intermittent grounding from the VSS output signal wire vibrating against the exhaust was making the speedo spike randomly to very high speeds.
 
joe_peters said:
Drop the sender in a pot of water with an ohm meter attached and a thermometer. Heat the water.

Application & Test Temperature Ohms
100 F (38 C) ...................................... 1365.0
220 F (104 C) ........................................ 93.5
260 F (127 C) ........................................ 55.1

If you want to test the gauge purchase a number of resistors at Radio Shack to equal the above values and use them on the sender wire.
Click to expand...

Used a pot to test these values and they were spot on. The gauge is working properly. The new thermostat, which is #4, behaves the exact same way. I might try one of those "balanced" thermostats or whatever, but I am pretty much ready to say that the thermostat is not the issue. This looks to be a somewhat common problem and its annoying the crap out of me so I'm planning on working my butt off until I figure this one out. Trying to keep the thread updates so if I do happen upon a solution it will be here and I keep track of everything that has been done so far.

Next on the list I is checking my O2 sensor for proper function (using ecomike's thread: http://www.naxja.org/forum/showthread.php?t=1012701) and getting the cooling system pressure checked, TPS and MAP will probably get checked as well. I need to solve that code I got from the key trick also although I'm pretty sure it doesn't have an affect on this issue.

Also, after attempting to ground to an engine stud (with no luck), I've decided to upgrade the ground going to the engine block and get rid of the woven steel strap.
 
good call on ditching the rear strap.

It's good that you're not actually having temperature problems, bad because now you're going to have to find the extra resistance in the harness
 
I still think the XJ is running too cool, needle used to be straight up 12 o'clock 210° and now it sits around 170. Now though I'm just pretty sure my gauge is accurate when its telling me the temp is 170° at the sensor.
 
If you are talking about the 91 in your sig, then you can take the jeep to a mechanic and have them read the CTS through the computer, while you compare it to the gauge. The CTS and gauge use different senders and outputs, so comparing them is a simple way to verify channel A vs channel B. If they show the same readings then you have a cooling problem, but if the CTS shows reasonable readings versus the gauge then you can isolate the gauge and sender circuit as your problem. Junkyard senders can also be useful, just have a handful of them before you tie up the mechanic's time.
 
I am having the same prob as posted runs about 150is just like in the photo. will get around 180 if it idles for about 20 minutes after getting it to 150. New everything upper hose, lower hose, bottle with new cap, Rad, thermostat stant premium,
waterpump and ZJ fan clutch. used to run hot but rad fixed it will do the test with a meter on the wires to check resistance.
but I don't think thats the prob heat is not hot just warm Soooo where should I start a new t-stat??????
BTW 89 renix stock closed? system
forgot to add electric fan is on a switch
 
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A new thermostat is cheap and easy so you might try a new one. Some people on here have fixed similar issues with a new thermostat. After that, I'm not sure where to go. I listed my next steps in here somewhere but haven't had the time to explore any further. I'll keep the thread updated with any progress.
 
Just looked at my radiator cap, its only 13lbs. Picking up a new 16lb one to test out. Then getting it pressure checked next week along with afore mentioned sensors.
 
i have the same crappy fuel milage in my 92... i ran the codes and it came back DC 22 wich was the coolan temp sensor so i replaced the one one the back of the head.. i think i did the wrong one i think its the one on the thermostat housing.
 
There might be something wrong with the wiring going to the temp sensor in your thermostat housing. Those resisrltor style sensors are usually pretty stout. A new one will run you about $14 bur there is a procedure fir testing it in the fsm. Let me know if you want to know how.
 
OkieXJ said:
There might be something wrong with the wiring going to the temp sensor in your thermostat housing. Those resisrltor style sensors are usually pretty stout. A new one will run you about $14 bur there is a procedure fir testing it in the fsm. Let me know if you want to know how.
Click to expand...
that would be cool.. i looked around in the manuals i have and it does not show anything. i will go and buy a new one anyways. the one thats in the jeep now to my knowlage has about 250 thousand on it anyways
 
I'm pretty sure my problem is a leaky head gasket. I had a radiator shop test my head gasket and they said it was good but I think it only tested for exhaust gasses. So I borrowed a pressure tester from auto zone that fits where the radiator cap goes. It leaked down pretty fast. I think there is a leak between an oil passage and a coolant passage which allows the coolant to vaporize and go into my crankcase and keeps it from reaching proper temp.
 
OkieXJ said:
I'm pretty sure my problem is a leaky head gasket. I had a radiator shop test my head gasket and they said it was good but I think it only tested for exhaust gasses. So I borrowed a pressure tester from auto zone that fits where the radiator cap goes. It leaked down pretty fast. I think there is a leak between an oil passage and a coolant passage which allows the coolant to vaporize and go into my crankcase and keeps it from reaching proper temp.
Click to expand...


so do you have oil in the rad or water in the oil?
 
I thought I just had sludge but now I'm sure its due to coolant in my oil. Its not milkshake consistancy like everyone says though, just some sludgy stuff on the very tip of the dipstick.
 
Yeah, that could just be from condensation in the crankcase.

Moisture buildup is "normal". Usually, if the engine is reaching normal operating frequently enough the oil will "cook off" the moisture. In extremely humid conditions, with a lot of cold starts and short trips where the engine get hot enough there will be some left over.

Change your oil more frequently--3 months/3k miles and use a diesel motor oil.
 
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