wrong timing can cause any engine to over heat. in fact if the timing is off it can cause hundreds of dollars of damage.
It could, but I'd start by checking the timing. If it's off the car will overheat, and that's easy to adjust. Heater cores are a grade-A pain to replace because you have to take apart the dash to get to them.
To far advanced may make it run a little hot but not over heat. You have some else causing it to over heat, give us more details.
According to the Gates website ( they make timing belts etcetera ) The 3.0 litre V6 engine in a 2003 Lexus ES300 has a timing BELT
Running it for long amounts of time, being in a dry environment, not having an intercooler, or any combination of the three.
No, a clogged heater core will not make it overheat. A leaking heater core will.
I checked the Gates website ( they make timing belts etc. ) and they don't list a timing belt for a 2005 Toyota Echo so it must be a timing chain . I did a Google search and the Toyota website shows the 2000 to 2005 Echo as having a timing CHAIN
usually white exhaust is caused by water in engine watch temp to make sure car does not overheat could also have a valve not seating properly did they replace all valves or just some of them
drive it without coolant
yes
There are marks on the chain that coordinate with marks on the timing gear. Make sure these line up when putting on the timing chain, and you should be good to go. Getting to the timing chain is the real battle.
Try changing the themometer
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