The best thing to do is to start as simple as possible, that way you don't end up replacing parts that you didn't need. So, here is an incomplete list of areas to check:
1. TB gasket
2. Coolant elbow coming off of the intake manifold.
3. Upper and lower intake manifold gaskets (check the front and the back of the intake manifold and look in the low areas and see if there is any coolant that has leaked out.
4. Check every hose and and hose clamp for evidence of leaking and tighten or replace as necessary.
5. Make sure your radiator isn't leaking.
6. Make sure your radiator/AC condenser fins are not full of road debris. (blocked airflow)
7. Make sure your belt is in good condition and that the tensioner is keeping correct tension.
8. Make sure your radiator fans are working. (You can test this by either waiting until your engine gets up to temp and see if they come on, or you can turn on the AC and watch to see if they come on, with the AC on they should come on right away.)
If all else fails go to an autoparts store like AutoZone and get a coolant pressure tester(loaner tool). With you engine cool, take off the radiator cap, put the tester on the radiator and pump the tester up to about 16-17 psi. Observe the gauge, it will hold pressure if there are no leaks. If it doesn't not hold pressure, check around and see if you can see any coolant leaking (check under the car to see it dripping, even look inside the passenger compartment, that will check to see if your heater core is leaking). Fix or repair what you find to be leaking. Sometimes it depends on how much coolant has leaked, but with leaked coolant all over the engine it may be hard to locate where the leak is, if this is true for your engine, make sure to clean the areas where here is coolant present and retest.
If the system does hold pressure move on to testing the radiator cap. The kit contains an adapter that is used for testing the cap. Put it all together and pump the tester up, careful to watch the gauge to see when the cap relives the pressure. You should hear the cap relive pressure about 15-17psi, if it releases it earlier your cap is faulty.
Good luck with finding out what it is making you overheat, if none of this works for you, there might be something more serious going on, like what Scotty was talking about (cracked upper intake manifold, which is very common for N/A 3800s or even possibly a head gasket). Either way let us know what the deal was.:th_thumbsup-wink:
