Funny thing happen today. My car overheated at idle speed. As long as I was driving the temp needle was fine, my resevoir filled up with boiling antifreeze. I pulled over and let the car cool down. Started back on the road, and turned the AC switch on so the fans will continouously run. The needle went back to normal and stayed there even at idle speed. I have changed out the temp control unit and put in a therma stat sometime ago. No fluid is comming from the weep hole in the water pump or anywhere else...Can anyone tell me what my problem is? and what is the correct temp for a new thermastat 170 or 180
degrees? I am currently running a 170, a saw a book that said I should be running 180, or does it matter? Thanks in advance for your help

 

Well, thermostats are easy to change and inexpensive. You should replace it again at least to rule out that as an issue.

 

are your fans coming on w/o the A/C?

 

Check that your WP belt isn't loose!

For the thermostate it doesn't matter if you get 170 or 180. There was a TSB that said you should use the 170 for better performance, but someone in the forum tested a bunch of 170 thermostates and found that they still open at 180!.

 

My fans do work, but I am not sure how often they are suppose to kick-in. I let the car run in the garage today at idle speed and it ran hot again, the resevoir filled up again. Is there a switch they may be bad that tells the computer when to kick the fans on? I will change out the T-Stat today once I get off. I hope that it is just sticking close; like you mentioned that would be very inexpensive to fix.

 

the CHTS (coolant head temperature sensor) plays a part in the fans coming on.
don't bother with the thermostat until you have your fans working correctly
pull the connector off the CHTS and see if the fans kick on then (failsafe system)
if they do then replace the CHTS, if they don't then check the relays
worst case scenario is that the regular speed on the fan is bad <- HIGHLY UNLIKELY

 

did you check the belt, as I suggested?

 

change the coolant temp sensor. i was also overheating at idle because no rad fans coming on. our cars dont have a fan switch, the fans are controlled by the coolant temp sensor & the ecu.

 

I did not get a chance to check anything on the car , much too busy at work.
I just left it parked until I get a chance to spend some time with it. The first thing I will do is check the belt, because I am hearing a squeal in the am when I crank it and it goes away all of a sudden, the belt could be slipping.
I will hold off on the replacing the T-Stat until I check the coolant head temp sensor as you have advised. One question though is the position of the CHTS sensor. I believe it is on the fire-wall side of the engine behind the temp control unit, correct? Is it a dealer specific part? or can I purchase it locally?
Thanks for all the advice.....I will look at it today for sure. I need my wheels!!!!!

 

it's a part available locally.
it's definately not dealer only

 

There are very few dealer only parts that you'd need really. either get what you need from internetautomart or a local shop, they should have it.

Make sure the fans do work when using the AC obviously, as they should kick on right away. Also there are 1 or 2 relays to check as well.

Brian wouldnt he be checking the Coolant Temp Sensor (CTS) and not the Cylinder Head Temp Sensor (CHTS) or both. Im pretty sure we have both.

~Alex

 

CTS=CHTS <- nissan nomenclature
there is a temperature SENDER for the gauge. easily confused

 

Also, check the wire from the coolant temp sensor. Mine was corroded through about 3 - 4 inches from the sensor connector under the sheathing.

 

Got around to looking at my car today. First, I checked my fan belts, all were loose so I tighten them car still ran hot at the idle speed. Next I replaced the CHTS. Took me about 20 mintues to drain, put in CHTS, re-fill and bleed system. No more over-heating at idle speed. The old sensor I pulled out was charred and has some corrosion at the electrical connector end, it looked as if it was blown. Part ran me about $30.00 bucks from the stealership, but I was quoted $100.00 plus at some others. Thanks for all your help, I am back on the road now......

 

and it's a $20 sensor lol