Temp gauges issues...

[ghettocruiser]

Hey everyone. Im having difficulty with my 94 XJ Sports temp gauge. 4.0 H.O. Ok, here is the deal. When i crank the engine, the gauges sweeps all the way to the right until the motor starts. Then it just sits down all the way on the left and wont move up. The motor is definetly heating up and coolant is flowing as it should. I bought a new sender...but I cant find where the sender is on the motor. I know its on the driver side at the rear of the head. I looked and I looked and I cant see or feel it. I dont even see any wires going up that way. Now...the motor isnt the original. It was replaced back in 97 with a new long block. It was the right motor because I have the reciept for the motor and I looked into the part number. Sooo... I guess my question is, is the sender really that hard to find? or is it possible the block doesnt have provisions and the plug for the sender is somewhere tied up? There are a few mystery harnesses around the engine bay, but I checked and none are for the sender. Let me know what you all think... Its the only thing on the jeep that isnt working as of now. Thanks a bunch.


Justin

 

[ghettocruiser]

Ok...now I feel kinda dumb...I think. I went outside since it stopped raining and checked again. I found a wire tucked up in the main harness. It had the right plug. So I stretched it to see where it went..and it wasnt very long. I was thinking the sender was on the side of the head or way in the back. But what I found was something that looked like a bolt head sticking in the very corner of the head. Once I wiped it off it looks like the old sender only snapped in half. So Im assuming the sender screws down vertically into the head??? So now that that is settled, I tried to get it out, and all it did was slip and round off. I was using a metric socket...is it SAE or something? Whats the best way to get it outta there without risking more breakage and headaches??? Sorry for so much typing...I get wordy sometimes.

Justin

 

[jneary]

when i remove them i use a half inch deep socket. if it is rounded off try driving a socket down on it that fits real snug.

 

[PaulJ]

The sensor has a brass body so use a 6 point socket, not 12 point.

 

[Eagle]

And don't remove it until you have a new one to install, or when the engine is hot, because it goes THROUGH the head surface into the water passage. Expect some coolant to squirt out, but if you pop that puppy with the system hot you're going to get a face full of boiling coolant and it won't be pretty.

 

[Dr. Dyno]

I was using a metric socket...is it SAE or something? Whats the best way to get it outta there without risking more breakage and headaches

Try using a spark plug wrench. I think it's the right size and it has a hexagonal pattern. Only remove the sending unit when the engine's cold. As an extra safety measure, remove the radiator cap SLOWLY to ensure that the cooling system is depressurized. That way you won't get scalding hot coolant sprayed all over your hands and face.

 

[ghettocruiser]

Thanks everyone. I was using a 12 point so that might be part of my trouble. I was also using a 13mm. I couldnt find my 1/2 inch, but I figured it was metric. Im pulling the valve cover today to re-seal it and replace the CCV system, so Ill mess with it then, the motor should be cool by the time I get things apart.


Justin

 

[ghettocruiser]

Ok...little update. Finally got the darn sender out. Had to use a bolt extractor on it. I wish I had a pic of what was left of that thing when i got it out. I threw it upon removal. You guys werent kidding about the coolant spraying out. I had the upper hose removed, and the rad cap and a heater hose. It still sprayed. All is well now. She gets up to temperature (210) really quickly. Kind of scary actually. Even went past for a couple minutes. Just when I started getting really nervous it came back down to 210. Hope it was just working out the air bubbles that Im sure I made today. Thanks for all the help.

Justin

 

[jneary]

if it operating ok now it probably was an air pocket. double check the coolant level when it cools down

 

[ghettocruiser]

I checked all my coolant levels, they seem fine. Today while just putzing around in the yard and what not the temp gauge was almost in the red. Right before the line at the red mark. I looked under the hood and the overflow was fine, no coolant coming out anywhere. Is it possible I still have air bubbles in my system? If so, whats the best way to get them out? Ive heard of "burping" the system, but Im not familiar with doing that. I never did it on any of my other cars. Or will the air bubbles eventually just work out after driving her for awhile? I havent actually taken it out on the road due to needing inspection. Let me know what the burping procedure is. Thanks

Justin

 

[Dr. Dyno]

I checked all my coolant levels, they seem fine. Today while just putzing around in the yard and what not the temp gauge was almost in the red. Right before the line at the red mark.

Was your electric fan running when the gauge went that high?

 

[ghettocruiser]

You know Im not quite sure. By the time I stopped it and popped the hood to check if fluid was coming out, the temp had gone back down some. I know the fan works because it comes on with the A/C. I just installed a new coolant temp sensor as well when I had the valve cover off. Im starting to think I just have air in the system somewhere. Its getting inspected wednesday tho so I have to sort it out before then. Im going to try running it with the cap off for alittle. I tried earlier but I got scared because coolant was starting to overflow from the radiator. Im not sure if thats supposed to happen like that or not. I got a new cap and thermostat that I need to install when I get a chance. Let me know on the correct procedures for "burping" the system or anything else I need to check out. thanks

Justin

 

[Dr. Dyno]

Your electric fan should also operate when the coolant temp. gauge reaches 220*F with the A/C switched off. You might wanna make sure that this happens.
There are two ways that you can "burp" the HO engine's cooling system. One is to park the Jeep with the nose downwards (or jack up the rear), remove the coolant temp gauge sending unit at the back of the head, and fill the cooling system until coolant comes out of the head.
The other is to park the Jeep with the nose upwards, detach the upper radiator hose from the t'stat housing, and slowly fill up the cooling system through the hose until coolant starts spilling from the t'stat housing. Replace the hose, top up the radiator with more coolant if needed and you're done.
Any remaining air will eventually be expelled into the expansion reservoir. Make sure that's filled up to the mark. You may need to add more coolant there until the self-burping process has finished.

 

[ghettocruiser]

Thanks for the burping advice. I just went out and tried that, and I did see quite a lot of bubbles come out. I let her run for awhile and the temp stayed just above 210. Then I took it for a drive and the temp didnt really rise. As soon as I pulled back into my driveway the temp shot up and the electric fan kicked on. It stayed right at the line before the red dash... I dont know what else to do. As soon as I drive it again it cools right back down. I have a new thermostat for it...but it needs to be inspected on wednesday. I wont have a chance to change it. Soooo Im hoping it passes inspection and emissions, then I think Im going to change the radiator, thermostat, cap, hoses etc. If it still does it after that then Im totally stumped. I have no idea how old the radiator is. It might very well have 170,000 miles on it... Who knows. There is always the change that the air still needs to get out...maybe after I drive it awhile for more than 5 minutes at a time. When I replace the radiator and all that other stuff that should atleast narrow that part of the system down. Thanks again... any more info is welcomed tho!!

Justin

 

[5Cent]

Ha, atleast you got your sender out! I torqued mine off in the head, so now I'm w/o a guage. All new radiator, hoses,tstat/tstat housing,etc...so i'm not as worried, but god I'd love to have it back! I'd say run yours down the highway for a few miles, watching the guage closely, then take her home, let her run for a few minutes in the driveway/shop where you can work on it and turn it off quick if she gets hot. If the air still isnt all out, you can try backwashing your heater core and cleaning out all the junk in there. Prestone makes a t-adaptor kit for the heater hoses. Clean and easy.

 

[Dr. Dyno]

As soon as I pulled back into my driveway the temp shot up and the electric fan kicked on. It stayed right at the line before the red dash... I dont know what else to do. As soon as I drive it again it cools right back down.

Your fans are not pulling enough air through the radiator. that's why the engine overheats when you stop and it cools down again when you drive off. Your electric fan should come on when the gauge is at 5/8. If it's not coming on until the gauge is nearly in the red, you need to change the coolant temp. sensor in the t'stat housing. Your viscous clutch of your clutch fan is probably shot and you'll need to replace it (or get rid of the clutch fan altogether and convert to dual electric fans).

 

[Eagle]

Your system may still have some residual air pockets that need to be worked out. However, in general if the temp stays down while the vehicle is moving and rises when the vehicle is stopped, that generally indicates that the viscous fan clutch is shot and needs to be replaced.

 

[ghettocruiser]

Thanks once again. Its kind of funny...I usually read all your ideas right after I thought the same thing. Last night at work I purchased a new radiator, new hoses, and a new fan clutch. I already installed a new CTS, and while I have it all apart Im going to replace the t-stat and radiator cap. That should just about eliminate any problems. Oh and a good flush out.
But...some good news. Today I drove it to get inspected and she started to overheat alittle while driving. I switched the heater on, which I havent done since I bought the thing for some dumb reason, and the temp almost instantly went back down to 210. It stayed there even after I turned the heat off. Sooo...I think that maybe helped get some more of the air out. If thats possible for switching on the heat.
It passed emissions and inspection!!! Time for fun now! Im sure you'll all hear from me with questions on some of my plans. thanks for all the help again!

Justin