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90 Corolla
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Discussion Starter #1
Now that the temp here in Portland has gotten into the high 70s, low 80s, my car is running even warmer. It was pinging yesterday and the fan ran almost constantly on the way home from work. Still no coolant loss or any other sign of bad things happening. Needle running about 10:00 on the gauge. Maybe a little more. This is just too warm for my tastes. It is going to get into the mid 80s to 90s before long. How can I determine of my radiator or water pump are OK? I am ready to just replace the radiator but I do not want to just throw money at the problem as I do not have a lot.
 

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iAzn
1988 toyo Corolla DX
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1,492 Posts
The water pump is all metal with rubber rings and bearings. There's a weep hole on it right behind it's pulley. If it leaks coolant from there and/or around the water pump itself, or make abnormal sounds and what not, it's time for a new one.

As for your radiator, make sure it's clean and the fins are not all dented and stuff.

For complete internal cooling system check, do a flush. If everything flows right, no clogs.

For antifreeze, buy the 50/50 antifreeze and fill the cooling system with that. Personally like the green 50/50 mix from Prestone, never done me wrong.
 

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90 Corolla
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Discussion Starter #3


Here is gauge at it's warmest.
 

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Looking at the needle it does seem a little on the warm side to me too. I am not sure of the accuracy of these gauges, I have been thinking of adding a quality digital gauge to get a more accurate reading of my water temp and oil pressure. Something that came to mind is maybe your thermostat is starting to go bad...maybe it is not opening all the way thus giving you a higher temp reading in hot weather but staying at normal with cooler weather.
 

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The Return of the Red Coupe
2010 RAV4 V6
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Yeah, it should sit at the middle... I'm also thinking thermostat, mine was stuck open so my car would be in warm up mode all the time.

Thermostats are cheap, change it first and if it keeps going then you'll have to keep troubleshooting... could also be the coolant is too old, when is the last time you got a flush done?

As for the rad, touch the fins with your thumb, if they're too easy to push in or they come right off the rad then it's time for a new one.
 

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90 Corolla
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134 Posts
Discussion Starter #6
Changed the thermostat, coolant and radiator cap a month ago. Used a Toyota stock thermo.
 

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Just a thought...what was the temperature rating for the thermostat you replaced? If the rating was higher than the original thermostat, then the gauge I believe would read higher than before.
 

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90 Corolla
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Discussion Starter #8 (Edited)
It was a stock spec, 180F. I am replacing the radiator on Sat. That should take care of it.

Just a thought...what was the temperature rating for the thermostat you replaced? If the rating was higher than the original thermostat, then the gauge I believe would read higher than before.
 

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Years of using aftermarket antifreeze and/or tap water in the cooling system causes mineral buildups inside the radiator core tubes that deminishes the heat transfer capability of the radiator.
 

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1992 Celica GT
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well because toyota antifreeze doesn't follow the laws of physics. genuine toyota ftw!


I have a similar problem, but I also have a new radiator without. I believe worn out coolant to be the culprit though.
 

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90 Corolla
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Discussion Starter #12
We shall see today. I will update you this evening on how it worked.
 

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90 Corolla
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Discussion Starter #13
Radiator changed nothing. Still running too warm. On top of that, the A/C sensor did not fit and the transmission cooler lines were too low. Had to modify them to get the thing installed.
 

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Is it possible to use some type of thermometer to get an accurate reading of your water temp? If the water temp is okay...maybe it can be a sensor that is out of whack.
 

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90 Corolla
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Discussion Starter #15
When this first started I stuck a candy thermometer in the neck of the radiator. The fan is supposed to come on at 96C/200F. It came on right at 200F. At the point when the fan came on, the gauge was showing the same reading as the above photo. I do not know what to do at this point.


Is it possible to use some type of thermometer to get an accurate reading of your water temp? If the water temp is okay...maybe it can be a sensor that is out of whack.
 

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I am thinking that it might be your water temp sensor. There is a simple ohmmeter test you can do. Check out page FI-155 of the shop manual.
 

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90 Corolla
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Discussion Starter #17 (Edited)
Are we talking the one for the gauge or the fan? I guess it doesn't matter. I will just check both. I will try that as soon as it gets light out. BTW, That manual has been very useful. Thanks.

I am thinking that it might be your water temp sensor. There is a simple ohmmeter test you can do. Check out page FI-155 of the shop manual.
 

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Are we talking the one for the gauge or the fan?
The gauge...

The sensor test for the fan is on page CO-21

Seemed like a funny place to put the gauge sensor on page FI-155 since I would not think to look there and just happen to come across it thumbing through the manual.
 

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90 Corolla
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Discussion Starter #19
I think this one does the gauge and the ECM. The one on the thermostat housing does the main fan and the one on the bottom of the radiator controls the A/C.

The gauge...

The sensor test for the fan is on page CO-21

Seemed like a funny place to put the gauge sensor on page FI-155 since I would not think to look there and just happen to come across it thumbing through the manual.
 

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I think this one does the gauge and the ECM. The one on the thermostat housing does the main fan and the one on the bottom of the radiator controls the A/C.
I am not sure of the sensor locations. Looking at the wiring diagrams at the back of the manual, pages 24-3 or 25-4 (depending on coupe or not) it shows the water temp sensor with a yellow/green stripe wire. Not sure how it ties into the ecm. Seems like a simple test though.
 
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