Monday, December 12, 2011

Replacing a thermostat?

I have to change the thermostat on my 2000 pontiac sunfire. I have absolutely no idea how to do this. Where is the thermostat located? I have the new thermostat to put in I just have to figure out how. It's kind of an emergency so any help would be very, very appreciated.Replacing a thermostat?
the thermostat is located right on the surface of the engine block where the upper radiator hose goes into the engine block. You can't see the thermostat because it's located inside the thermostat housing, which is the metal tubing that the upper radiator hose clamps onto on the engine.

First locate your upper radiator hose. This is literally the hose that comes from the top of your radiator. You'll see a second hose on the radiator, but it will be at the bottom. Follow the upper hose to where it meets the engine block. That is the thermostat housing and it will have to be removed. However, you have to drain the radiator fluid a bit otherwise it will leak all over when you remove the housing.

Before going any farther, back in the 60's and 70's when engines were basic and uncluttered, changing the thermostat was an hour's job, tops. On todays' vehicles it can be a daunting task if only because there is so much clutter in the way. If you have no idea how to do this, you may be better off with the assistance of someone who knows. If you don't install it correctly you risk severely damaging your engine by overheating it.

I'm not familiar with the motor in the 2000 sunfires, in that I don't know what obstacles will be in your way, but the basic premise will still be the same.

1. Only do this while the engine is COOL.

2. Jack up front of car and secure car on some jackstands

3. remove radiator cap and locate radiator drain plug (this will be at the bottom of the radiator somewhere.

4. Place a large clean oil pan or the like under the drain plug. Open the drain plug and drain out 1-2 gallons of radiator fluid.

5. Follow the upper radiator hose to where it attaches to the engine body. You may have air intake apparati in the way that you'll have to remove first.

6. Remove or loosen the clamp on the upper radiator hose that connects it to the thermostat housing and pull the hose off the housing. Be ready here as some antifreeze may leak out that was trapped in the hose. If it looks like a lot is still coming out, reattach it and drain more fluid.

7. The housing will be connect to the engine block by two bolts, usually. Remove these two bolts. As you loosen them, if coolant starts leaking out around the housing, you need to drain more out.

8. With the bolts removed, you can remove the housing.

9. Now you should be able to see the thermostat. Take special note of how it sits and is installed in the body. Note that the spring will sit INSIDE the engine block.

10. Lift out the old thermostat. Carefully scrape the gasket mating surface to remove traces of the old gasket. If the surface isn't clean, you won't get a good seal and it will leak. Be careful not to knock any material into the block.

11. If it calls for it, rub some non-hardening gasket sealer on the new gasket and put it in place.

12. Set the new thermostat in the engine block in the same orientation as the old one (spring side goes down)

13. Bolt the thermostat housing back on, getting it tight but not so tight that you crack it.

14. Reconnect upper radiator hose.

15. Make sure your radiator drain plug is tight.

16. Rather than use the coolant you drained, it's best to put in some new coolant mixed 50/50 with distilled water. Add almost as much coolant as you removed.

17. Keep your radiator cap off and start the car. There will be air in your coolant system so now you'll have to purge the air. As the car runs, it will work the air out. You'll see the coolant bubble and foam like it's almost going to overflow (and it might a little bit) but this is just air getting worked out. After this happens you'll see the level drop down a bit, so add more coolant. Do this until all the air is out of the system. When the car is cool you should have coolant run over into your overflow reservoir, although rarely do I ever see cars with anything in the reservoir.

18. Replace the radiator cap (use a rag to hold it so you don't burn yourself.

19. Watch your temp gauge to make sure your car isn't running too hot for the next several times you drive it (well, theoretically you should always do this).

20. If you want to check your old thermostat to see if it was faulty, this can easily be done by putting the thermostat in a pan of water and heating it up on the stove. Put a cooking thermometer in the water and observe what temperature the water is at when you see the thermostat open up (if it even does). Most open up around 195 F. If your thermostat is faulty it won't open up, will just barely open up, or might require much higher temp before it opens up.

The engineering behind a thermostat is very simple as there is a wax plug inside that melts at a certain temperature. As it melts the spring moves which opens the valve, allowing the hot coolant that was only circulating in your engine to now run into the radiator and cool down and THEN cycle back into the engine.Replacing a thermostat?
follow the top radiator hose and you should run into the thermostat housing. drain the anti-freeze, take out 2 bolts out of the housing and lift it up, clean both the housing and the intake of any old gasket, put the thermostat in with the spring into the intake, put some sealer on the housing and the intake, put the gasket on the housing, put the housing on and tighten the 2 bolts, fill the radiator and you good to go.
I don't know where you got the info from on a bad thermostat.

The guy above me described how to find it.

The basic malfunction of a thermostat is this... The temp starts climbing after startup, then finally goes down after it reaches a hot temp. It works fine after that.

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