oz37k Posted November 16, 2011 Report Share Posted November 16, 2011 Its been a while since I posted. Well after reading several posts. I am still puzzled. I have a 1995 Monte Carlo Z34 with the original LQ1. Back in 09 when I got the intake gaskets done I had a brand new ECT installed, I guess this is the sensor that turns on the fans right cause I cannot locate any other switch for the fans. I have bleed the system via the service manual as well as tried squeezing the upper hose with the bleed valve open and then close it and let the hose go. My A/C does not work so I cannot turn it on and have both fans kick in to check but I do not overheat if I am driving but when I am idling for a while I notice the temp almost reaching the last white line before the red line on my temp guage before the primary fan kicks in. When I check with my laser temp guage pointed at the thermostat housing the temp is usally 235-240 when the fans seem to kick in. Is this normal? Is it a symptom of a bad thermostat or radiator cap? Quote Link to comment Share on other sites More sharing options...
Artemis Posted November 16, 2011 Report Share Posted November 16, 2011 There are 2 sensors for coolant temperature. One gives the reading to the ECM and gauge, its attached to the Lower intake manifold. The second one controls the fans, and its bolted to the side of the front head, under the crossover. You should try replacing the second one, its a single wire sensor. Most parts places will try to sell you the one that goes into the LIM, make sure you get a sensor with one wire and a little clip at the end. Quote Link to comment Share on other sites More sharing options...
oz37k Posted November 16, 2011 Author Report Share Posted November 16, 2011 There are 2 sensors for coolant temperature. One gives the reading to the ECM and gauge, its attached to the Lower intake manifold. The second one controls the fans, and its bolted to the side of the front head, under the crossover. You should try replacing the second one, its a single wire sensor. Most parts places will try to sell you the one that goes into the LIM, make sure you get a sensor with one wire and a little clip at the end. Is it on the driver side or passenger side of the head? Quote Link to comment Share on other sites More sharing options...
Crazy K Posted November 16, 2011 Report Share Posted November 16, 2011 (edited) WRONG INFO HAS BEEN POSTED the proper term for the part is usually CTS (coolant temperature sensor) In a 1995 and older 3x00, 3100, 3.4dohc, 2.8 there are TWO sensors. the first is in the intake manifold. The second is on the driver's side of the head on a 3.4dohc LQ1. CTS in intake: feeds info to the PCM/ECM, controls the fans. the fans are controlled by the ECM/PCM based on the temperature that sensor detects, and the settings that the computer is set to. CTS in head: feeds info to the instrument cluster, and there can by two versions of that sensor based on whether the car is equipped with an actual gauge or not. In a 1996 and newer 3x00 a single CTS is used in the intake that does all temperature sensing functions. there would be no sensor on the corner of the rear head. NEXT.... the fans do have different temperature settings based on whether the A/C is on, and the first fan to turn on is always the driver's side fan. the other fan is secondary and turns on about ten degrees hotter than the first fan. The temperature you are seeing does seem high, if you are not seeing the driver's fan turn on, that is most likely the fault. If the fan does turn on then something may be miscalibrated. FURTHER MORE.... a custom tune chip may help alleviate the problem(assuming everything else is in working order) with colder fans turn on calibrations. The only person I would inquire this of would be ROBERTISAAR, he has made chips that can work the 95 LQ1. Edited November 16, 2011 by Crazy K Quote Link to comment Share on other sites More sharing options...
oz37k Posted November 16, 2011 Author Report Share Posted November 16, 2011 WRONG INFO HAS BEEN POSTEDthe proper term for the part is usually CTS (coolant temperature sensor) In a 1995 and older 3x00, 3100, 3.4dohc, 2.8 there are TWO sensors. the first is in the intake manifold. The second is on the driver's side of the head on a 3.4dohc LQ1. CTS in intake: feeds info to the PCM/ECM, controls the fans. the fans are controlled by the ECM/PCM based on the temperature that sensor detects, and the settings that the computer is set to. CTS in head: feeds info to the instrument cluster, and there can by two versions of that sensor based on whether the car is equipped with an actual gauge or not. In a 1996 and newer 3x00 a single CTS is used in the intake that does all temperature sensing functions. there would be no sensor on the corner of the rear head. NEXT.... the fans do have different temperature settings based on whether the A/C is on, and the first fan to turn on is always the driver's side fan. the other fan is secondary and turns on about ten degrees hotter than the first fan. The temperature you are seeing does seem high, if you are not seeing the driver's fan turn on, that is most likely the fault. If the fan does turn on then something may be miscalibrated. FURTHER MORE.... a custom tune chip may help alleviate the problem(assuming everything else is in working order) with colder fans turn on calibrations. The only person I would inquire this of would be ROBERTISAAR, he has made chips that can work the 95 LQ1. Thanks. So the one I have to look at is the one on the Intake right. When I disconnect it, both fans kick on and my Engine light turns on. Maybe the one for the guage will need replacing, must be giving wrong temp. By the way, when the car is off and the temp is high, will the fans kick on while the key is out of the ignition or only when the car is on and running? Quote Link to comment Share on other sites More sharing options...
Crazy K Posted November 16, 2011 Report Share Posted November 16, 2011 that is a very good question, which has no solid answer... and part of the reason is programming. GM has a TSB that affects this question, they had some issues regarding power surging damaging fan relays when the car shut down, such that the correct procedure was to re-program the fans to run during and past shutdown.... but they should be off within a minute. i would have to find the details i once read, but essentially a different PROM memcal would be installed at the dealer with slight different calibrations. Quote Link to comment Share on other sites More sharing options...
oz37k Posted November 17, 2011 Author Report Share Posted November 17, 2011 Thanks for all the information. I found the sensor in the head and while looking yesterday at the sensor in the manifold I noticed that the yellow wire's insulation has started to peel. I hope there is not a break in the wiring. By the way, where is the needle supposed to sit when the fans should turn on, pics would be appreciated. Thanks, Oz37k Quote Link to comment Share on other sites More sharing options...
digitallyphoenix Posted November 17, 2011 Report Share Posted November 17, 2011 the thermostat and rad cap dont control when the fans turn on. i know on the 96 Z the fans kick in around 210 and 220 iirc. if it were a 96+ i would say you could get someone to flash a new tune in with new fan settings... but the only other options i can think of are: a) swap to a cooler Tstat and check for blockage in the radiator. this wont be the reason for the fans not kicking in but might be why its getting that hot. wire in a relay so both fans come on instead of just one. Quote Link to comment Share on other sites More sharing options...
oz37k Posted November 28, 2011 Author Report Share Posted November 28, 2011 Got to bleeding the system this weekend. I ordered new bleeder valves from GM part no. 10070107, way better than the originals. I followed the manual and man was there alot of air in the system. I keep reving it until all the air bubbles stopped and only coolant squirted from the valves. Then this morning I did the hose squeeze method and no air was in the as only coolant came out as soon as I squished the hose. So I will see if the fans come on sooner when I drive home today. Will report back. Quote Link to comment Share on other sites More sharing options...
oz37k Posted November 29, 2011 Author Report Share Posted November 29, 2011 Update: Still coming on late. Could the PCM be fried? I checked the Factory Service Manual for my car and it states that at 223F the first fan kicks on and the secondary at 235F. Could it be the relays are not correct for my application? Any help would be appreciated. Quote Link to comment Share on other sites More sharing options...
BrianK82 Posted November 30, 2011 Report Share Posted November 30, 2011 Might I suggest back probing the CTS connector with a Ohm meter and verifying that the resistance signal correctly correlates to engine coolant temperature? That sensor was new in 2009, maybe its calibration has since become a little incorrect, and it is not relaying the correct resistance values. The only other option is to find someone with a compatible scan tool and reading the CTS value there. You should be able to find a resistance/temperature chart in the service manual for the vehicle. Hope this helps!! Brian K. 94' Cutlass Supreme Convertible, LQ1 3.4 DOHC Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted November 30, 2011 Report Share Posted November 30, 2011 I have often checked the CTS with a scantool using this method... Let the car sit for at least 8 hours undisturbed. Connect the scantool, but DO NOT START THE CAR, just turn the key to "run". Then, use the scantool, and see what the ECM is getting for the coolant temp reading. It should be within a few degrees of the air temperature outside (since the car hasn't been running for a long time). I'm betting if you do this, you'll find the sensor is underreporting coolant temp. Cheap and easy check! Quote Link to comment Share on other sites More sharing options...
oz37k Posted November 30, 2011 Author Report Share Posted November 30, 2011 Galaxy500XL, Thanks. What scan tool are you using? Quote Link to comment Share on other sites More sharing options...
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