What could cause this? Already replaced the thermostat

 

too lengthy to list.

use the search function, there will be lots of posts.

 

Check all your hoses to your water pump. You should be able to squeeze them very easily. If there hard that means there's most likely air in the system and an air bubble in the water pump can cause it to overheat because it's not running properly. If this turns out to be the case you should start by flushing the system cause that would be alot cheaper than most other options

 

If it's a 2000-2001, watch out for the dreaded head issue. Mine was venting combustion gases into the coolant, and had to be replaced because it was cracked. Compression was fine, so don't let this fool you. I believe there are test strips that can be used to check the coolant for this....