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Matt, Mechanical Engineer
Category: Toyota
Satisfied Customers: 21995
Experience:  BEng, Repaired my own cars and others for 20 years, worked in Formula 1 for 10 years
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Car is overheating after driving and coming to stop,

Customer Question

car is overheating after driving and coming to stop, radiator fluid level good, tstat changed , think is fan speed not correct
JA: Have you checked the coolant? Have you checked for a leak in the cooling system?
Customer: not seeing any coolant on ground, did put in resv and checked in radiator which was full
JA: What is the model/year of your Toyota?
Customer: 2005 rx330
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: i replaced radiator last year ,took to mechanic to replace water pump,all rad hoses(including transfer hose under throttle body,tsat
JA: Anything else you want the mechanic to know before I connect you?
Customer: showing codes b1181 and b2799
Submitted: 2 months ago.
Category: Toyota
Expert:  Matt replied 2 months ago.


As a very first check make sure the coolant level is correct / up to the mark on the tank, then I'd first check that the radiator cooling fan is coming on as it should and if thats OK then replace the thermostat in the engine.

Whilst the thermostat is being replaced you might as well also reverse flush the cooling circuit (remove top hose to rad and use a hosepipe to push water into the engine until you get clear water out of the radiator hose) and top up with 30-50% fresh antifreeze. Also check that the small diameter bleed hoses that run from the top of the radiator and the top of the engine aren't blocked as this allow the air to vent back to the header tank automatically.

If you still have a problem then check that the water pump impeller / turbine isn't spinning on its shaft. You should be able to achieve this by removing the bottom hose from the engine and use a screwdriver or similar to feel for the water pump impeller blades, whilst your assistant turns the engine over by hand.
If you can stop the impeller with slight pressure from the screwdriver the pump needs replacing.

Also its possible the belt is slipping so its worth replacing its especially if the rubber ribs are cracked or it looks shiny on flat side of the belt - while its off check that the tensioner and other pulleys all spin freely the exception to this is the AC pump ( if fitted)

I'd also suggest ensuring that you've got all the air out of the system as this sort of episode can leave pockets of air trapped and prevent the coolant from circulating properly.

So check that the small hoses that run from the top of the engine and radiator that run back to the header / expansion tank are free flowing and not blocked

If these are OK then remove the tank pressure cap and run the engine from cold with the heater set to full hot

As the engine starts to warm, squeeze the large hoses running to the radiator to help displace any air - all the time keeping an eye on the level in the header tank, making sure it doesn't drop below the minimum and open any bleed screws built into the top cooling hoses - closing them off as soon as they start to gush water

Once the engine is up to temperature the tank should be quite full. Switch the engine off and leave it to cool

Then top up to the mark once its all cold and replace the cap

Customer: replied 2 months ago.
My wife is running it up and down the hill where we live and she is going to bring it back and I'm gonna see if the radiator fans are coming on
Then I was going to remove the electrical connections at each radiator fan and supply 12 V to see if they span one fan seems to be making a little noise and doesn't spin is freely as the other fan so I'm thinking it could be that or the sensor that turns them do you know how to test the sensor
Expert:  Matt replied 2 months ago.


if the electric fan doesn't spin freely then there's something up with it and this could well be the issue

its not uncommon for a unused fan to seize up

the fans are switched on by th eECM once it sees a high coolant temperature

the coolant sensor is on the engine very close to where the radiator top hose is connected

and you can measure the sensor resistance changes with temperature, according to the attached image, if its different to this then replace the sensor

Expert:  Matt replied 2 months ago.

do you still need help?
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