Overheating

Look in your radiator with the engine running, you're looking for turbulence and/or bubbles.

My first taco had no heat when I bought it, bled the system, no heat. I assumed a stuck open thermostat. But I found it had no thermostat at all. Installed, and instant overheating. Checked the rad, and bubble bubble. If you're lucky, bad head gasket.

I had a cracked head, ended up just replacing the entire motor.

 

What this goy said

 

overheating after replacing all components is likely head gasket based on the two cars I had with warped heads. the tracker would overheat after driving on the hwy or if it was at idle for too long... the stealth would just eat up oil and coolant until it would overheat. the latter was easier to deal with and allowed me to drive the car a few years before ditching it.

 

I don't know if the OP still has the overheating, but I thought I would post this for anyone else that has this problem. This is is from my 2005-2009 Tacoma Haynes manual, some of these causes have been mentioned, but others haven't and this can be used as a reference for others:

Overheating causes:

1.) Insufficient coolant in system.

2.) Drive Belt defective or not adjusted properly.

3.) Radiator core blocked or radiator grille dirty or restricted.

4.) Thermostat faulty.

5.) Fan not functioning properly

6.) Radiator cap not maintaining proper pressure. Have cap pressure tested by gas station or repair shop.

7.) Defective water pump.

8.) Improper grade of engine oil.

9. Inaccurate temperature gauge.

 

Since you've replaced like 4 t-stats, that is NOT your problem, unless you're putting them all in wrong.

What does your oil look like? Milky? that's a blown head gasket. Odd that the Haynes manual doesn't mention that...