If it has a conventional fan driven by the belt , replace the viscous fan hub ( fan clutch)
if electric fans . fuses, relays and water coolant temp sensor to be checked
if the over heating occurs at stop lights , slow moving traffic, hard pulls in low gears , and you have a viscous fan hub , it will be the hub
SOURCE: Overheating
Having the radiator rodded is a good move. Retest. If it has an electric radiator fan check temp sensors. If the fan has a clutch it may need to be replaced if its slipping with the engine hot. Check bellts. Its likely a fan air flow issue if the engine overheats when the care is not moving or is moving slowly. If the engine overheats only with AC on that narrows it down. Write back if that's the case. Lots of things can cause this. Antifreeze and a good radiator cap discourages boiling. Pressure in the radiator raises the boiling point but it can't build up pressure if the cap is bad. Antifreeze also raises the boiling point. If actual boiling happens in the engine then steam builds up in critical places and drives the collant out of the block making the engine even hotter than it already is. Replace the cap. Check the antifreeze.
SOURCE: overheating after changing the head gasket
Yes, due to many things.
No ....1 Did you replace the thermostat ?
Take out the thermostat, and pop it in a saucepan covered in water, bring to the boil, and see if it opens, this will confirm if this is the fault.
If not..............
1. The cooling system must be topped up, and pressure tested to max running pressure 15lb sq in.
If there is an external leak this will show it up, possibly from cooling or heater hose, water pump, radiator, or the heater matrix.
If nothing is apparent an internal leak, must be then suspected, ie head/s or head/s gaket/s.
2. To test out this , a carbon monoxide test, should be carried out on the cooling system, by passing, a sample of the cooling system gas, when engine is at normal running temperature ,through the test fluid in the vacuum tester.
If the fluid changes color, this is proof the combustion chamber gases are escaping into the cooling system, which over pressurizes the system and normally blows the coolant out of the header tank overflow, as you drive along, and you do not see.
The other symptom of this problem, is the coolant leaks back into the combustion chambers, when the engine is switched off, and when you start later, a misfire is noticeable until the spark plug dries out.
Also if the plugs are removed, and after 1hr of cooling system pressurizing, the engine is spun, any coolant from the plug holes will confirm head, or head gasket failure.
I hope it is the thermostat....?
Let me have your thoughts !
Good Luck !
A FixYa rating is all I require...Thanks...John.
may be oil feed to cylinder head replace gasket
SOURCE: Toyota Tazz 1300 2004 overheating - Have replaced
have you replaced the thermostat? This controls the engine temp
SOURCE: i have a toyota noah 2003 model 1AZ engine with
My noah 2003 keeps showing the exaust sign and Eco on the dash board screan, what could be the problem?
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