My engine temperature gets very high making the coolant boil. In the last 2 weeks I have changed:
1) Fan relay
2) Engine coolant temperature sensor
3) Intake Air Temperature (IAT) sensor and
4) Water pump/timing belt
5) Steering pump

I am about to change the thermostat too.

I checked, the wires to the fan coolant temp sensor and the IAT sensor and get the expected 4.8 V and a good ground. Wiring to the fan relay was fine except a poor ground which I re-grounded. The fans come on when the A/C it turned on and also when the engine is hot and idling. Don't know if they come on while driving.

Regarding the thermostat, the return hose gets very hot which lets me believe that at least it opens some of the way if not fully.

I performed a pressure check and there is no leak in the cooling system (holds 15 psi for at least one hour when I disconnect the pressure gauge). I see no visible leaks when is cold or hot except when it overflowed from boiling too hard.

I am at my wits end as to why it is still overheating. Can it be that the PCM is not working?1?....How could I know if the computer is bust?

Also the only error code I get is P0113 that the IAT has High Voltage. Cannot erase the error codes so Check Engine is always on. I heated the sensor and its resistance changes as expected. Wiring checks good as I mentioned.

Would deeply appreciate any help.

 

How about the condition of the radiator? Fairly fresh and presumably clean radiator tubes?

 

When does it overheat? Idling? Stop and go city driving? Highway/Interstate (60+ mph)? A/C on of off? When it overheats does turning the heater up at full fan lower the engine temp?

 

I had the same thing happen on my previous 05. One of the radiator dual cooling fans wasn't working. Replaced the assembly and the problem went away

 

Thank you for your interest. It overheats at 40-60 mph but, since I never left it idle for more than 20 min, it could be overheating at idle. However, as I mentioned, at idle, I saw the fans kicking in so it might not be an issue at idle. The temperature rises very fast once it has reached the middle of the range and I immediately pull to the side and turn the engine off. So, I do not know if turning the heater up to full blast would help take away enough of the heat build up to cool the engine down but, even if it did, it would be of little help since I cannot be driving with the heater up at full blast all/most of the time.

 

djetelina,
Thank you for your interest. The radiator is the original. When I examined it from the outside I did not see any significant bents or gauges. I even cleaned it from dead bugs that are typically there. No leaks there either. Do you know of any way i could check its inside condition ? Thank you

 

Hi stephenjxn,

Both my cooling fans are working 1) when powered directly from the battery 2) when normally connected via the cooling fan relay (which was replaced with a new one) when the A/C is on and when the the A/C is off but the engine is idling.

 

Thermostat should be near the top of the list for replacement. It is possible it is not opening fully. Note, do not use the 'failsafe' model;a number of posters on other forums have noted they are not very reliable. Stick with the oem temp rating for the thermostat.

Overheating at highway speeds indicates the radiator is not doing its job well. This could be dirty radiator fins or a gunked up radiator. The engine is producing more heat than the radiator can get rid of. The fans have very little effect as the forward motion of the vehicle will push more than enough air through the radiator to keep the temp in check.

Pulling the upper radiator hose may give you enough access to check the inside.

Turning on the heater when overheating is for diagnosing the problem not for driving.

 

Update.

New thermostat and thermostat housing installed. Problem has not solved. Cooling fans come up regularly and radiator hoses to the engine and the return to the cooling reservoir are getting quite hot. After about 20-30 min at idle at an ambient temperature of about 60F the temperature gauge passes the middle of the range and it steadily rises until it reaches a line below the red while the fans are at this point run continuously. At this point, the coolant in the reservoir has expanded very close to the cap and I turned the engine off.

 

It is very likely your radiator needs to be replaced as you noted the fans are running continuously and it still overheats. The radiator does not seem to be able to do its do its job