My 2002 Diamante has 118K miles and I just completed its second timing belt change and this time replaced the water pump. Prior to this service the car would run very hot when stopped in traffic. I had already replaced all hoses the two electric fans, thermostat (twice to make sure that wasn't the issue) and the radiator (as it was already showing signs of stress cracks in the top tank). I have also checked the coolant mix and I am still getting overheating when stopped in traffic. As soon as I can get out of traffic and the temp comes back to normal (center of gauge). This symptom seemed to be related to the electric fans being the problem, but Both fans are operating. I also swapped a couple of the Fan Relays (that control fan speeds) just to make sure and the symptoms did not change. I am not losing coolant and it is staying clean so I don't believe I have a bad head gasket. I have also replaced the radiator cap.

Please provide some additional ideas on what can isolate this issue.

Thanks

 

Hello,

I had the same problem recently.

1) Check your trans fluid it may need to flush.
2) check your thermostat it may not functioning properly.

I hope these will help.

 

i second thermostat.
Also, turn off aircon.
or,turn on the heater, full heat, any fan. See what happens.

 

I second the A/C, if turned ON, 2 fans must be ON at low speed.

 

I replaced the thermostat twice.. and no change. Both fans have also been replaced and also verified that they turn on at the correct times, such as when A/C is turned on.

I just changed out the Temperature Sensor as the next possibility.

But...Given this overheat issue only happens with a very high outside temperatures (Phoenix Gets HOT.. Ambient above 95 degree F) I can not verify if this fixed the problem.

Thanks for the suggestions :-)

 

Since the problem goes away when you are out of traffic, i.e. moving, the one thing that is changing is the amount of airflow through the radiator. You have verified that the fans are running, but are they running at the correct speed? Also, have you checked for debris clogging the fins of the radiator or condenser coil, preventing proper airflow?

I should mention that I had a very similar problem that I traced to an inoperative main radiator fan. I found a foreign object jammed between the fan blade and the radiator. Removing the foreign object and replacing the resulting bad fuse, fixed the problem.

The good news is that I found the wrench I had been missing...

 

I certainly agree on your points. I have replaced the radiator with a brand new OEM denso because the top plastic tank was starting to show stress cracks. Also Both electric fans have been replaced. As it wasn't obvious on how I could test the different fan speeds I simply swapped the fan "Speed" fuses to see if I could Isolate a bad fuse. All fuses appeared good. Both fans do turn on properly.

This last resort of replacing the Temperature sensor is based on suspecting that it fails at high temperature and then shuts off or reduces fan speeds at higher temps???

In this cooler season here in Arizona... I do not have any overheating symptoms. It needs to be at least High 90's or greater to experience the issue.

Thanks for the input !

 

By the way.. I also performed a full tranny flush per Rame2013 suggestion. I had swapped the Thermostats twice and the Temp Gauge responds consistently during warmup.. so the thermostats appear to be functioning correctly.

Now that I have the original Temperature sensor replaced, is there a test procedure I can perform on it to verify if it is good or bad ? I hate to wait until HOT weather to find out if I still have the problem... and get stuck in traffic with an overheat condition.

 

As far as I can remember what I did to my Diamante 2000 about the overheating issue are the ff:

Note: diamante overheating is based on the gauge reading in the meter which appears above normal but it doesn't mean that the engine was stopped and smoked out.

1) I change the oil - overheating
2) I replace the thermostat - problem persist.
3) I replace the coolant sensor - overheating
4) I replace the temperature gauge sender - overheating
Both fans where okay, I test relays are okay.
5) I replace replace the radiator - overheating
6) I flush the coolant (of course) - overheating
7) I flush the transmission fluid. - problem seems to disappear.
8) I replaced the radiator pressure cap. - after thorough test(driving), problem solved.

@ Diam20002 - good luck buddy. you will gain skills and technical experience in your repair projects.

 

Thanks Rame2013 for a review of the comprehensive list of changes you made to solve the issue on your Diamante.
Given I have covered that list and that this issue with my car only appears during excessive ambient operating temperatures I am beginning to suspect my Air conditioning system may be suspect. I had work performed recently that required replacement of the expansion valve. I am suspecting the condenser is operating at extensive temperatures due to improper pressures (?) in the system. This may be causing the coolant radiator to be less effective at cooling.

Any thoughts on that as a potential?