I got the infamous "---" on my DIC for engine temp the other day, then later threw a code for "coolant below thermostat operating temp" and knew for sure I had a thermostat stuck open. Since I don't see where anyone here has done a walkthru, thought I'd add one.
It's a simple job on the 2.4, and only costs 20 bucks for the stat, and 10 bucks worth of dexcool.
Don't try this on a GXP, as the manual shows you need to pull a vacuum on the coolant system, (GE-47716 method), before refilling it or else you'll get air trapped in the system.
Here is the manual description for this, copied from a post by JR,
1. Drain the cooling system. According to the manual, you need to do the block drain for the thermostat.
1. Remove the surge tank cap.
2. Raise and support the vehicle.
3. Place a drain pan under the right side lower radiator mount.
4. Open the radiator drain cock.
5. Drain the cooling system.
6. If a complete block drain is required, place pan under the water pump drain.
7. Remove the water pump drain plug.
8. Drain the cooling system. After draining, tighten the drain bolt. 22 N-m (16 lb-in)
2. Remove the air inlet grille panel.
Prelim: Remove wiper arms.
1. Remove washer arm nut cap. use small flat tip screwdriver/tool
2. Remove washer arm nut. Hold the blade when applying torque. 32 N-m (24 lb-ft)
3. Remove washer nozzle hose from wiper arm.
4. Use slight up and down motion at the hinge to remove the arm.
5. When re-installing, position wiper blade at top edge of the windshield blackout.
1. Air inlet grille retainers (remove all 10)
2. Disconnect washer pump hose at the outer edge of the air inlet grille panel.
3. Remove air inlet grille.
3. If engine oil cooler perform following steps, otherwise proceed to step 8.
8. If vehicle is not equipped with engine oil cooler, reposition the radiator outlet hose clamp at the thermostat housing.
9. Remove the radiator outlet hose from the thermostat housing.
10. Remove the radiator outlet hose clip form the outlet hose bracket.
11. Remove the thermostat housing cover bolts and cover. (JR - the bolts are a bit of a pain to get to. Use a long extension and push the hoses aside to get on the bolt heads. I think it's a 10mm. Torque 10 N-m / 89 lb-in when re-installing)
12. Remove the thermostat.
13. Remove and discard the O-ring.
14. Install new thermostat and put it all back together!
Now, I'll show pics of me doing most of these steps.
Allright, the draincock is easily accessible and opens by hand.
The waterpump drain plug was not where I've seen it in drawings of the waterpump. This may be because my car is an early build. The plug was on the bottom of the waterpump, facing downward. You can't see it in this picture, but you can feel it on the bottom and it's easy to get a socket on.
Next is the wiper arms. Removing the cover and nut was easy. I was stumped for a couple of minutes on removing the arm though. The "slight up and down motion" description in the manual should read, "grab it at the hinge area, and yank up and down fairly hard" I had been babying it.
Then remove the screws on the inlet grill panel, along with the 3 plugs on each end, 2 of which are here:
and one of which in inside the door area:
Then just lift up the panel, watching out for the water squirter tube on the drivers side.
Unhooking the water squirter tube was proving a pain, so I just positioned the panel out of the way.
Here's the thermostat housing on the back passenger side of the engine.
The instructions call for removing the hose, but as the clamp was awkward and stubborn, I just removed the housing bolts and voila..
Now, my high-tech method of raising the surge tank to refill
You can see the thermostat inner gasket is what failed.
Make sure you have an assortment of socket extensions for the thermostat housing bolts. It's awkward and cramped back behind the engine. And if you drop something, it probably will wind up on the transmission crossmember, requiring you to jack the car up. (don't ask me how I know this)
The thermostat housing bolts are also not cranked down tight at all. Make sure you don't overdo it, or you might cause a leak at the o-ring.
There you go. Hope someone finds it useful.