Glad I found you all from the OS
I have had a few issues on my 03 I6 TB which has just over 143k miles on it. I picked this up new, but now drive only for longer trips with the wife and stepson and gear ( beach stuff or snow skis) the Check engine lite came on during one of these trips this spring, and I troubleshot by activating OnStar, and having them read/troubleshoot the trouble. code reported had me check coolant, and noticing the temp gauge on dash was a bit low, I changed the thermostat. I ordered the sensor too, (from Rock Auto) but did not change it, because I did not have the right socket. i did have fun moving the alternator around. anyway, fast forward to early July, drove to Cape cod and on the way, it was over 100 degrees, and in traffic the AC would cut out. while up there, noticed the water pump crapped out, and being 500 miles from home had the local garage change the water pump. they only charged me $500 and kept the screws that attach the fan faring to the radiator. after I got back, i had a the local firestone place (who sold me a lifetime alignment) charge the AC by weight and include leak check. I was back to the Firestone place a few ,more times. noted the temp gauge bumped up on the trip uphill in the mid 90s, so i changed the fan clutch. (another story, but not too bad) I changed the shocks and struts, and since I used the monroe with springs, let them check the alignment. they told me the toe in was out but tie rods were frozen ( which I verified while changing them, i am the proud owner of a Leslie tie rod tool set), also changed sway bar ends and the front and rear brakes. along the way the fuel pump crapped out, rusted and leaking. sprayed gas all over the inside of the recyling place where I dropped off the struts and disks. mostly cause i had just filled the tank, and was three days from a beach trip, I had it towed to the dealer, having read someone had consideration from GM for part of the repair last year (on the OS, I think) they only charged me $1800, including fuel filter, lines and the new pump. the tech tried to talk me into also having them replace the drive shaft, since it is a bit rusty, and would have made his job to drop the gas tank easier! I could not find any report of anyone who broke a drive shaft driving on the road, so told him to stay the heck away from the drive shaft. (estimate was another $900 and five days to ship)
anyway, the trip to the beach was only in 90 degree weather, and for the most part, the ac was ok, but I did note that it did cut out in slow traffic, and when it did, the dash temp gauge bumped up a few notches. I will take the TB this weekend and monitor the temps on this trip. I picked up an OBKLinkSX and ScanWiz from scantool.net. they have some more expensive software and modules required to read all the fan readings, but i am on the fence whether I want to pay for the software upgrade. I now think perhaps I should have changed the temp sensor. someone suggested overconcentrated coolant could cause trouble. perhaps the waterpump guy put straight dexcool in. should I check the specific gravity of the coolant? I think the AC could just be cutting out because it thinks the engine is too warm. either that, or the compressor craps out in the heat. since the temp gauge has started to indicate high temps when the AC kicks out, I think it may be coolant is getting too warm. I also have an IR thermometer I will take along and check the real temp if it acts too warm. I do not expect it to get much over 90, so this may have to wait till the spring, unless it really quits. I suspect the radiator may be clogged, but not sure and am getting tired of random part changing. anyway, thanks for reading. glad I figured out where you guys went.
my TB is turning into a hobby. I am on the one hand pissed I have had to do all this work, but on the other hand, I like the wrench turning. would be more fun if I did not have to keep my tools in the basement. I have put more into this thing than it is worth, cash wise, but should be good to go if I can figure out this coolant/ac issue. ( I probably should change the transmission cooler lines, they look a bit corroded.)
The generally accepted method is to remove the alternator to get to the t-stat and sensor, so you might as well replace both and call it good. It'd suck to replace the t-stat, button it up and then find out it was the sensor and do it all over again. I paid about $30 a piece for the parts on Amazon, cheap insurance to replace both.
