dracon79 Posted May 17, 2007 Share Posted May 17, 2007 I have an 88 jeep comanche 4.0 with a 5 speed tranny. When the engine idles it would stay at 180 or so. It has a 180 thermo in it. After driving it then I idle it would go to like 230-240. So I replaced the coolent temp sensor and the coolant guage. Now when I idle before driving it, it goes to like 220 after driving it and I idle it goes to like 270. But I don't hear any gurgling and no fluid increase in the resv so I am at a loss. I think its the guage still even know I replaced it. I shot one of those infrared temp readers at the thermy housing when the guage was reading 270 and the reader showed 216 the hoses were all at about 170-180 so I am very confused. Link to comment Share on other sites More sharing options...
Duner Posted May 17, 2007 Share Posted May 17, 2007 You could have a grounding issue, if the motor is running ok and there are no signs of over heating I would start checking all of the grounding points on your wires before I remove the guage ,besides cleaning and checking the grounds makes everything else work better. Link to comment Share on other sites More sharing options...
Oizarod115 Posted May 18, 2007 Share Posted May 18, 2007 at 270 if you shut the truck off a) the pressure bottle cap should've popped and squirted out excess pressure and/or warped/effed the bottle B) you would more than likely have leaks from hell. sounds like its the gauge to me Link to comment Share on other sites More sharing options...
DirtyComanche Posted May 18, 2007 Share Posted May 18, 2007 What's 270 in *C? I buried my temp gauge once, eventually it stalled when I put the clutch in to shift gears... Umm, anyways, bad gauge... And a 180 stat is low, I think mine is a 198...? Link to comment Share on other sites More sharing options...
dracon79 Posted May 19, 2007 Author Share Posted May 19, 2007 yeah thats what I figured so it must be some kinda of grounding issue/electrical problem... Link to comment Share on other sites More sharing options...
Renegade Posted May 20, 2007 Share Posted May 20, 2007 I'm gonna hijack this post for a minute. My 89 4.0 just has an idiot light that's been coming on lately. I also lasered it & temps were normal, so I purchased a generic temp guage at Napa. Now for the question I'm scared to ask. Where is the temp sending unit & how hard is it to get at? I just popped the hood & looked around. Only thing I saw was what I assume is the oil pressure sending unit(next to the filter & behind the distributor). I guess I should put in an oil pressure guage while I'm at it. Link to comment Share on other sites More sharing options...
Wildman Posted May 21, 2007 Share Posted May 21, 2007 Renegade - Check this out, bottom of the topic page, and Thank CWlongshot for the pictures ;) http://www.comancheclub.com/forums/view ... nding+unit Temp gauge is a single wire, rear of the intake manifold, near the firewall, drivers side. Link to comment Share on other sites More sharing options...
Renegade Posted May 22, 2007 Share Posted May 22, 2007 Thanks and UH-OH!! Today I cut the wires off a sensor I thought(until now) was the temp sending unit. It looks exactly like the sensor in the 3rd pic except it is located on the side of the block right by the drivers side motor mount. Crap. What have I done :mad: So when I find the correct sensor, will the generic Napa guage I bought thread in? That's the problem I ran into today. The sensor I yanked has 3/8 pipe threads. The guage has 3/8 flare threads. I cannot find an adaptor for this. Link to comment Share on other sites More sharing options...
Eagle Posted May 22, 2007 Share Posted May 22, 2007 Thanks and UH-OH!! Today I cut the wires off a sensor I thought(until now) was the temp sending unit. It looks exactly like the sensor in the 3rd pic except it is located on the side of the block right by the drivers side motor mount. Crap. What have I done :mad: So when I find the correct sensor, will the generic Napa guage I bought thread in? That's the problem I ran into today. The sensor I yanked has 3/8 pipe threads. The guage has 3/8 flare threads. I cannot find an adaptor for this. UH-OH indeed. That is the temperature sensor that sends data to the ECU. Without that, your ECU will be running in open-loop ("warm-up") mode all the time. It'll run ... but it'll be using a pre-set fuel map that's richer than optimum and your fuel economy will suffer. Either that, or you just cut the wires off the knock sensor. Both are located on the driver's side of the block. Link to comment Share on other sites More sharing options...
Wildman Posted May 22, 2007 Share Posted May 22, 2007 If you have a 3/8" flare fitting on the gauge from Napa......that will not work. The right one has a 1/4 or 5/16" straight tread on it, and a "screw" end for the one wire to slip on......the part is AC Delco C1861 cool temp Indicator, switch. http://www.partsamerica.com/ProductDeta ... 90&PTSet=A If you cut the wires off the wrong sensor, I hope you can repair it, as Eagle stated, it one of two important sensors that will change the performance of the engine. Big time. If you can not splice the wires back, you need to change the cut sensor out also. And why cut wires???? most all of the sensors have pull apart connectors with lock taps near the sensor, or up line. If your in doubt which sensor you "cut" take it to the parts store and have the guy look it up, and check it out on the counter. Link to comment Share on other sites More sharing options...
mjcanoe Posted May 22, 2007 Share Posted May 22, 2007 Wildman, 2 sensors on driver side of block. The sensor w/pigtail is temp. The sensor w/ a plug on connector is knock sensor, it looks like the connector for injectors & sensor body is longer then temp. sensor. mjcanoe Link to comment Share on other sites More sharing options...
mjcanoe Posted May 22, 2007 Share Posted May 22, 2007 dracon79, there are ground wires on the passenger side of block behind & above oil filter. I believe 2-3 wires on stud that dipstick tube bracket is attached to block. these will at times affect sensors. If you choose to go aftermarket gauge, get '91 up t/stat housing & add a "T" for that sensor. Works great for my mj. mjcanoe Link to comment Share on other sites More sharing options...
Renegade Posted May 23, 2007 Share Posted May 23, 2007 I cut the wires because I couldn't fit a closed end wrench over the connector. The open end was rounding the head & I don't have a 3/4" line wrench, so I hacked it. Just to clarify, the sensor I pulled out has to be another temp sensor since it was in a coolant flow. I think the knock sensor is lower, just above the oilpan. I'm gonna see if I can get a new replacement sensor through Jeep, then I'm gonna remove the CORRECT one ;) BTW, A guy in my club has a spare sensor like the Delco one mentioned above, so I should be good to go. Link to comment Share on other sites More sharing options...
Eagle Posted May 23, 2007 Share Posted May 23, 2007 Just to clarify, the sensor I pulled out has to be another temp sensor since it was in a coolant flow. I think the knock sensor is lower, just above the oilpan. That would be correct. The knock sensor goes into a dry hole in a boss just above the oil pan flange. So you killed your computer's temp sensor. As I wrote, it should still run, but it'll most likely always be in open loop mode, meaning it won't know when the engine has warmed up so it will constantly run according to the pre-mapped fuel curve (i.e. rich) that's used for warming up. I don't think it'll hurt the engine, but it sure won't do wonderful things for your fuel mileage. I don't think that sensor interchanges with the one for the gauges in the head, due to a vastly different ohm range. So you are wise to bite the bullet and go to a dealer. The parts chains may not even be aware that the Renix era XJs and MJs have two (different) temp sensors. Link to comment Share on other sites More sharing options...
Wildman Posted May 23, 2007 Share Posted May 23, 2007 Renegade - I can see why you cut the wires now......makes sense. I would follow Eagle's advice on the sensor you need to replace, you can't go wrong with taking it to the dealer's part department and get the correct sensor that you need. The good news is you did not cut the knock sensor.......that little tiny sensor would run you $70 plus to replace :eek: Lesson learned......move on. Link to comment Share on other sites More sharing options...
Renegade Posted May 25, 2007 Share Posted May 25, 2007 I have the replacement sensor ordered for $27. Not too bad. I also ordered the above mentioned A/C Delco sensor then realized the obvoius. I need an electric temp guage & I have been trying to make a mechanical guage work(the type that has a copper tube with the nipple directly connected to the guage). I've always used the mechanical type before & never gave it a thought, but it won't work in this application. Link to comment Share on other sites More sharing options...
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