coolent temp sensor 07 tb 4.2 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

rhswarrior04 · #1 12-30-2011, 10:37 PM

im trying to replace the coolant temp sensor on my 07 trailblazer lt 4.2L ive looked at past posts on this site that say it is just above the thermostat but its not there from what i can tell its on the back of the motor on the passanger side any ideas how the best way to change this would be very helpful reason for replacing is im have a problem with the idle jumping while parked or sitting at stop light took it to dealer hoping it would be under warranty they say it is the thermostat, coolant temp sensor, air pump, and the air pump check valve

TrailblazrI6 · #2 12-31-2011, 08:46 AM

From what Ive read, its behind the alternator and hidden so you wont be able to see it unless you remove the alternator.

I havent touched mine but have had to remove the alternator before. Its not hard - remove the serpentine belt, take off the black bracket in front of the alternator, there are 3 bolts one is hidden. Take off the little bolt that holds the a/c line on. Then, there are 3 bolts that hold the alternator on, IIRC. Remove those 3 bolts and swivel the alternator out of the way.

rhswarrior04 · #3 12-31-2011, 10:48 AM

Quote:

Originally Posted by TrailblazrI6

From what Ive read, its behind the alternator and hidden so you wont be able to see it unless you remove the alternator.

I havent touched mine but have had to remove the alternator before. Its not hard - remove the serpentine belt, take off the black bracket in front of the alternator, there are 3 bolts one is hidden. Take off the little bolt that holds the a/c line on. Then, there are 3 bolts that hold the alternator on, IIRC. Remove those 3 bolts and swivel the alternator out of the way.

I had already removed the alternater to replace the thermostat and when I didn't see the temp sensor there just above it I started looking around the motor to find it am I'm pretty sure its on the passenger side towards the back looks like its just above the heat shield for the exhaust manifold where the heater hose and the line for the air pump check valve run later I will try to post pics thanks for any help you can give

TrailblazrI6 · #4 12-31-2011, 01:32 PM

Quote:

Originally Posted by rhswarrior04

I had already removed the alternater to replace the thermostat and when I didn't see the temp sensor there just above it I started looking around the motor to find it am I'm pretty sure its on the passenger side towards the back looks like its just above the heat shield for the exhaust manifold where the heater hose and the line for the air pump check valve run later I will try to post pics thanks for any help you can give

Nope. It is on the drivers side of the engine block, right above the t-stat, behind the alternator. You obviously didnt look hard enough because its got wires going to it and is RIGHT in the way of the thermostat.

rhswarrior04 · #5 12-31-2011, 04:28 PM

here is a pic of the thermostat and i cant see where the sensor is it should be just above thermostat in the area of that round piece of the block with the flat end im not sure if maybe they have changed the engine some time between 02-07 but i even looked in the haynes repair book and it shows it to be in the location that you told me it was but i cant see it there thanks for any other help you could give me

TrailblazrI6 · #6 01-01-2012, 12:55 PM

I can see the wiring harness going to it!! Come on now. Feel around - follow that wiring tube I can see - it will go to the block to the sensor. Did you even look at those diagrams I posted?

No, they did not change the location of the sensor at all, and especially it would make no sense at all to put the sensor on the side with the exhaust manifold. It needs to be near the thermostat jacket.

The sensor is hard to get at. I think you are expecting it to stick out like a sore thumb like most other engines, but it does not in ours.

rhswarrior04 · #7 01-01-2012, 05:06 PM

Quote:

Originally Posted by TrailblazrI6

I can see the wiring harness going to it!! Come on now. Feel around - follow that wiring tube I can see - it will go to the block to the sensor. Did you even look at those diagrams I posted?

No, they did not change the location of the sensor at all, and especially it would make no sense at all to put the sensor on the side with the exhaust manifold. It needs to be near the thermostat jacket.

The sensor is hard to get at. I think you are expecting it to stick out like a sore thumb like most other engines, but it does not in ours.

this is a diagram i found that shows it where i thought it was and a pic to compare that mine is not the same as this one so they obviously did change the sensor location sometime between an 02 and the 07 my question is whats the easiest way to get to it any help would be greatly appreaciated

TrailblazrI6 · #8 01-01-2012, 11:39 PM

Quote:

Originally Posted by rhswarrior04

this is a diagram i found that shows it where i thought it was and a pic to compare that mine is not the same as this one so they obviously did change the sensor location sometime between an 02 and the 07 my question is whats the easiest way to get to it any help would be greatly appreaciated

Not sure where you got those first diagrams but that is not our engine. I found it on the web too at a very generic website and there is NO reference to that going to the 4.2l I6 Atlas engine. The coolant temperature sensor location never changed on the 4.2l engine.

However, your last picture shows the temperature sensor, right above the t-stat, behind the alternator. I can clearly see it. Good luck.

TrailblazrI6 · #9 01-01-2012, 11:57 PM

Quote:

Originally Posted by rhswarrior04

here is a pic of the thermostat and i cant see where the sensor is it should be just above thermostat in the area of that round piece of the block with the flat end im not sure if maybe they have changed the engine some time between 02-07 but i even looked in the haynes repair book and it shows it to be in the location that you told me it was but i cant see it there thanks for any other help you could give me

Its ABOVE that metal round piece. I can see the wire going to it

After this, I would give up working on cars. I dont think its your thing....

rhswarrior04 · #10 01-02-2012, 11:44 AM

Quote:

Originally Posted by TrailblazrI6

Its ABOVE that metal round piece. I can see the wire going to it

After this, I would give up working on cars. I dont think its your thing....

Incase you didn't notice the wire that you see in the pic of my motor is also on the other pic it runs to the throttle body I'm by no means an expert but I'm not a rookie at working on cars either you should by now know that anything gm dies shouldn't surprise anybody to make things difficult to work on they want you to take it back to the dealer everytime somethings wrong