2000 Toyota Camry - What next?

I changed the thermostat. Now it overheats and heater doesn’t work. Does it have an air pocket? How do I fix it?

If the vehicle is overheating, then it’s quite possible that you’ve got a blown head gasket. Pretty common on early 2000’s camrys. Might even be a warped cylinder head.

Before jumping to any conclusions…first purge any air out of the system. There are tests that can be done to determine if the head gasket is blown.

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Why did you change the thermostat?

Check engine light was on and the code said that’s what it is.

How do you purge the air out?

Put ( Purge air in cooling system ) in your search engine and you will find articles and videos that walk you through the process.

there are codes for engine taking too long to heat up. but i dont think there are codes that specifically say the thermostat is “bad”? engine too hot?

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A code will rarely ever tell you what specific part to change!!!

If you were over heating, you may have a blown head gasket.
If you fill the radiator and watch the coolant…if you see bubbles…the head gasket is shot.

Are you sure you did not put the thermostat in upside down???


To remove air from the cooling system, get the engine up to operating temperature.

While the engine is idling, loosen the upper radiator hose clamp and take a small flat bladed screwdriver and slip it between the upper radiator hose and the radiator hose neck.

Allow the engine to idle until all the air is purged and nothing but coolant comes out.

Remove the screwdriver and tighten the hose clamp.


Ok. Thank you.

FYI . On many vehicles the code definition for an engine taking too long to heat up, says faulty thermostat. The reason for this is the only way an engine can take too long to warm up is a faulty thermostat.

FYI . . .

I’ve also seen P0128 caused by low coolant level

If it wasn’t overheating before you changed thermosta, make sure you have correct thermostat, make sure it isn’t upside dowwn. To properly purge air from system you need to find the highest part of the cooling system. It is usually at the fill cap. But if the only place to fill it is at the radiator, there may be a bleeder screw near the top of engine. Opening bleeder screw with engine running will force air out. It is best to look up proper bleeding procedure. And follow them. Works every time.

I could see that happening if coolant is low enough or should I say vaporlocked to the point that there is no coolant at the temp sensor. Air at sensor would signal a cooler temperature then what it really is. That also could be scary as the engine could over heat without a clue until steam blew from radiator cap

Replacement thermostats sometimes fail right out of the box. Whenever I install one I check it first in a pot of hot water on the stove to make sure it is opening at the correct temperature and opens the correct dimension. I’ve found stuck closed new thermostats doing this. If all else fails remove the thermostat and test it like that.

The way I remove air from my Corolla’s cooling system is drive the front wheels up on ramps, then open the radiator cap and idle the engine until the radiator fan turns on. If the coolant in the radiator is then a little low I’ll top it off. At that point the dash temp gauge should be in the normal temp range. Then I install the radiator cap.That’s all there is to it the way my particular car is configured. If you plan to do work on your own car you should have a repair manual, at least a Chilton’s or Haynes. That will explain Toyota’s recommended procedure how to air bleed the cooling system on your own car. It will also show a diagram how the thermostat is supposed to be oriented. There are two orientations that must be correct. If there’s a little hole, it should usually go up, not down. And the part that bulges out should face the correct way, either toward the engine, or away from the engine, depending on what the repair manual says. Most diy’ers take careful note of the thermostat’s orientation when removing the original.

A faulty thermostat usually doesn’t throw a code. Are you sure it wasn’t a coolant temp sensor or cylinder head temp sensor?

Most of the thermostats that I have replaced were because of a fault code, an engine not up to temperature will have a higher emissions output, therefore the fault. Even some OBDI vehicles set a fault for engine not reaching temperature.

Good info on this thread. Good to know. Thanks!