Ok so my check engine light came on and one of the codes was p0128, if I remember directly.basically bad thermostat, so I bought another one to replace it. I didn't see a how to so I thought I make one. First thing first, this is a pretty simple job just takes patience and flexible hands.
Difficulty:3 out of 5 not to hard just tight squeezes
Tools: extensions long and short ones. 10mm deep socket or small ratchet.
Time: took me about forty five minuets.


There some sensors you have to disconnect to get enough space to get in there not sure which sensor this one is but its right in front of the drivers side

The next couple sensors are located in between the valve cover and black fuse box remove three, the blue one orange, and black one.the black one is a little tricky.



Now that you have some room get your socket and ratchet and begin to remove the three bolts on the thermostat housing. The bolt in front is the hardest one to get to this is how I positioned my ratchetThe ones on the back are a little easier get your extensions and remove those two. There's the in total don't forget!


After you get those out don't bother removing any hoses there a pain and I didn't want to deal with them.gently Pop out the thermostat cover of some water will come out but don't freak out.this is how I put the cover off to the side

Now that that's out of the way grab some pliers or some kind of hook and pop out the old thermostat, and replace with new one. Now just fallow the instructions in reverse and your done.
Sorry if this write up is sort of crude I did it all on my phone.

Hope this helps someone! Cheers!

 

So the thermostat is essentially directly mounted on the driver's side of the block (the end) about half way down the block towards the ground?

 

That's how I did mine a few years back.

Nice job!

 

Nice write up. Thanks!

 

Good write up

 

I pulled the same P0128 CEL code as the OP. My outside temperature on the DIC read "---", and my coolant temperature was reading "---" even after I replaced the coolant temperature sensor. I bought a new thermostat (AcDelco and verified part number). I used this helpful guide to replace mine and figured everything out smoothly with a few exceptions.

Firstly, I since I have a 2006 Cobalt SS N/A 2.4L LE5, I don't have the blue sensor at the bottom of the 2nd picture. Techinically not a problem, but just noting that even though this is a guide for the 2.0 LSJ, it does apply to the 2.4L LE5.

I feel that removing the mounting bracket for the black and orange/blue sensors in the 2nd picture (which I think is an 11mm or 12mm) would make reaching down to the thermostat much easier, and would only require removing one bolt.

Next, I know you said there would be some water and not to freak out, but I had water that smelled like coolant, and had a rainbow in the puddle, so I know it wasn't JUST water. In either case; There was a substantial amount of fluid coming from the thick hose attached to the top of the thermostat housing (I believe it runs to the radiator). When I removed the old thermostat, I could see more fluid where the bottom of the thermostat sat.

Finally, upon clearing my CEL code and starting my car, my outside temperature still read "---". My biggest concern is that my coolant temperature was reading, and after a few minutes of driving (after I worked on it while it was cold) it started at 160 degrees, and ended up saying I was running around 244 degrees. I've never had it run that hot. However, when I popped my hood it didn't feel like it was 244 degrees (I've worked on my car a lot, and would know the differences between cold, 120 degrees, 160 degrees, and 200 degrees). Plus, when I turned on my interior vents to try to cool it (directed at feet and head, turned temperature straight in the middle, no defrost, no A/C), it felt slightly warmer than outside (about 60 degrees). I've had my car blow a fuse for my front cooling fan, and the highest my car has ACTUALLY been is 220 or so. When I open the vents like I previously mentioned, the air was so hot it made breathing difficult..

Any solutions to my problems? Thanks.

-------------------------

Problems solved.

'---' reading on outside temperature - the sensor was unplugged under the drivers side headlight. the plug is green and blue and goes into the underside of the black headlight mounting bracket.

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The temperature issue - when I disconnected the top part of the thermostat housing and all of the water/coolant came out, I essentially drained the coolant, therefore didn't have any coolant, yet I still beat on it at the track.. FML it's okay for now. I added a full gallon of coolant last night.

 

Thanks guys

 

Don't need to use any gasket or anything right just pit the top cover off and swap thermostats and put cover back on?

 

Yep, that's it.

A new thermostat comes with the req'd gasket.

 

So there a bolt you got to take off on the can sensor

 

No. You don't touch the cam postion sensor housing.

I guess you can remove some sensors to make more room.

I didn't when I change my thermostat a few years ago.

 

Ok cool thanks I got to do mine today. Didn't have any leaking issues did you

 

My thermo actually didnt fail on my car. The gasket some how tore, and leaked coolant out of the the thermo housing.

Since replacing the thermo I've had no issue at all.

 

Oh yeah I think mines going it say 174 at one time then 150 the next.

 

Thanks for posting this man, good how to. I am not very mechanically inclined but still managed to pull it off haha!

Thanks,
Cody

 

Sub

 

Great write up. I would also like to add that the General Motors plant decided to position the hose clamp on the rubber hose to where you cannot get a socket over the bolt. Might need an adjustable pliers.

 

Id like to add an update to this thread for anyone interested. There are two different styles of thermostat's available for all ecotec motors. While most part's websites will not list these two, they are GM equivalent and aftermarket upgrade tstats for our cars.

You can find gates or stant thermostats in two different flavors. OE Exact and OE Type. Both of which are 180 degree thermostats, both behave differently in terms of the amount of coolant they can flow, and the rate at which they open. If you are looking for OE cooling characteristics then you want to use the OE Exact thermostat which is an exact replica of the OEM GM replacement (Alternate/OEM Part Number(s): 12615097, 12622410, 131139, 55350941, 90537453).

The OE Type thermostat is a slightly larger thermostat with a heavier spring and upgraded weir valve. This thermostat will open to full faster, and close faster as the car cools down, thus maintaining a lower operating temperature using the thermostat alone. These two style of thermostats are sold by GATES and STANT (under the brand name "superstat"). Both are made by the same manufacturer. Stant describes the superstat (gates OE "type" style) as the following...

Stant's SuperStat® uses a high flow venturi for maximum cooling capacity during high temperature, high load operation and employs a unique Weir Valve® for precise flow metering during cold weather, light load operation to ensure stable temperature control under all conditions.

The high strength stainless steel flange is burnished to a bright finish for additional stress relief and added corrosion resistance.

The Stant SuperStat® thermostat is also thicker than most competitor thermostats and our standard reverse poppet thermostat for added strength and longer life.

The power element of SuperStat® is comparable to those used in heavy-duty trucks. Its actuator piston is larger in diameter than the standard thermostat and competitive product. This larger piston delivers 1 1/2 times the power of our standard thermostat and almost 2 1/2 times as much power as the competition for enhanced durability and longer life.

The opening spring of the Stant SuperStat® thermostat is designed with a load that is 50% stronger than our standard reverse poppet thermostat. This heavy-duty spring helps return the thermostat to the closed position and prevent cold running, even under the most adverse conditions. Features and Benefits

Using the navigates system (NaviGates) gates lists the following part numbers for the 2006 Cobalt SS.

OE Exact Thermostat - 180° Reverse Poppet (2 17/64" x 11/16" x 1 3/16") w/1 Seal Part# 34025

OE Type Thermostat - 180º Reverse Poppet (2 17/64" x 7/8" x 1 13/64") w/1 Seal Part# 33943

ACDELCO also offers a replacement thermostat for our car's, the ACDELCO thermostat eliminates the use of the center seal for when the thermostat gets stuck. This is often the seal that people find missing around the center of their thermostat. I personally do not recommend using this as the replacement as that seal is there for a purpose in case of failure, Coolant is still allowed to pass by the tstat.

Why upgrade the thermostat you ask? Well a 160* thermostat is just far too cold for these car's to run efficiently. 180* is perfect, but the way the OEM tstat behaves, most people find consistently average coolant temps above 200 degree's. While the cooling fans themselves dont turn on until above 220 on most car's.

This upgraded thermostat along with 70/30 (water/coolant) coolant and a bottle of water wetter from redline. My car will average between 192-195 at idle in traffic in even the hottest weather. Never having the need to get close to the temp the fans turn on at.

Here's a couple pictures for reference, a blown OEM thermostat on the left vs a brand new gates oe type 33943 180 degree tstat.

 

Thanks

 

nice

 

Thanks for clearing up the 160* idea I had. Still trying to learn sideways engines.

 

I got the Gates OE Type thermostat. I don't see a difference yet. But I just took it for a 20 minute easy drive.

I removed the oil pump. I don't see how you guys did it otherwise.

Anyone else use the OE Type?

 

Why would you remove the oil pump.... lol

 

It makes the job 100 times easier.

 

It's not hard to do at all with everything left in place.

I wouldnt dick around removing more than you have to....