ACDelco GM Original Equipment 15-11073 Engine Coolant Thermostat and Housing Assembly

OEM Thermostat for my 2004 Colorado. My truck used to run about a little over the 1/4 mark on the temp gauge but with this thermostat it is now closer to the half way mark which is indicative of the update they did to these to bring them up to 195 degree instead of 180. I was getting a P0128 code so my original thermostat was stuck open.To replace this, loosen your lug nuts on the drivers side wheel, jack the truck up on the drivers side, place a jack stand underneath the frame rail for safety, remove the wheel and the wheel splash shield held on by 6 plastic clips. Place a bucket or a catch pan underneath the truck and remove the lower radiator hose at the radiator. This will allow you to get rid of the old coolant that can accumulate sludge. Then also run a gallon of distilled water through the radiator and let it drain out. Also remove overflow bottle and drain that and clean it.I used two 9 inch long 1/4 extensions along with a swivel 10mm 6 point socket to remove the bolts. Once bolts are out pull the old thermostat housing away and the hose off the truck, so you can then have access to remove the stubborn clamp better.. Make sure you remove the old o-ring if it stays on the engine block. Wipe clean the mating surface. Put it all back together and fill with almost 2 gallons of Dex-Cool which you can also get on Amazon for a great price.I got rid of the stubborn clamp and used 2 regular worm type clamps I purchased at Vatozone. Easier to deal with than the OEM clamp.Tightening them from underneath the truck with my long extensions. Truck now runs about 2 tick marks shy of half way.

Fits on replacement of original thermostat, functions great.

Good thermostat, good price. Like everyone else, I got a P0128 in my 2005 Chevy Colorado 5cyl. I don't think my original thermostat stuck open, but rather lost its calibration. Driving around with the scan tool connected, I was topping out at a steady 165 degrees everyday. Gauge showed around the 1/4 way mark. I think my normal was just below the 1/2 mark. This new thermostat is said to be a little hotter and it is. I'm now at 196-200. Gauge slightly above the 1/2 mark.Install was ok. I did not remove the tire. I had enough room to work around it. I did remove the wheel well piece. 10mm and some extensions and a universal to remove the stat. If I used my little 1/4 inch drive set, I probably could have gotten away without the universal joint. The bolts were not super tight, I could easily loosen them without putting any muscle behind the wrench. The factory clamps were a bear to release with channel locks. I removed lower hose from radiator and left it still attached to thermostat. Just guide it out from the wheel well. Remember the path you took. I purchased a new hose too, didn't want to take a chance that I might need to cut the old hose. I assembled new hose and stat to the same position as the old and guided it back into position. Holes lined up and hose was in a good position too. I used a little piece of tape to hold the bolts to my wrench for reassembly, and that was it. Factory clamps were the biggest pain of the job. I had regular hose clamps on hand, but just reused the factory clamps. No way they will ever snap or leak. If you choose not to mount the hose to the thermostat outside the truck, you might want to remove that tire so you have more room to struggle with the clamp.The check engine light went out on the next morning drive as soon as it warmed up, so don't reset the code if you are coming up on inspection in a heavy handed emissions state like NY.

Fixed my issue of to cold coolant temp. I had a check engine light for coolant temp being too cold. My old thermostat was stuck open tank goodness instead of shut bc I could still drive it while the part came. It was the perfect fit and it has been in my truck for at least three years, so I'm gonna say the quality it very good. It returned the Heat level back into operating range!!

Worked great and resolved my issue.

Similar to Sparky's review, I bought this thermostat for my 2005 Colorado (4-cyl) which seemed to have a low coolant temp at normal run. The thermostat was original equipment and the truck has around 160k miles and it seemed to take a long time for the heater to warm in winter. I would occasionally get a PO128 error (coolant taking too long to warm) and the coolant would hover around 160-170 F at 1/4 mark on the temp gauge (I keep a scan gauge plugged in). The replacement keeps the coolant around 198-200 deg, just above 1/2 on the gauge, which should be the normal operating temp. Not having the truck from new, I don't know what the original 'normal' operating temp was and the truck seemed to do fine at 165 except for the PO128. I've read that apparently GM changed the 'normal' operating temp from lower to higher to aid in emissions and increase MPG shortly after 2005. The thermostat comes with the o-ring as seen in the photo, there is no other gasket or sealing required. R&R for this and both radiator hoses took a couple hours because I wasn't in a hurry. It's a simple matter of removing left front tire and splash shield for access. Would be nicer if the radiator had a drain, but removing the lower hose from the rad does the trick. Don't bother trying to remove the hose from the old stat, just unbolt and take the hose/stat off together. Some hoses have a white line to line up the hose with the stat top vane to keep the hose positioned correctly, the hose I got with this stat did not. It was a bit of work to get the new hose on the stat in the correct position, but having it positioned correctly made the bolt holes of the stat line up cleanly with the mount holes in engine (hose is one-way and position is important - new stat to hose, stat to engine, hose to rad... done). You can find a detailed R&R with photos on the 355 nation website (the GM frame code for this truck is 355) tech area; how to's; performance and maintenance.