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Am I hurting nything?

26 June 2000
Lauderdale by the Sea, FL, USA
Most of you know that i posted a topic a while back about my temp guage going down when driving in cool weather..... we all fnally agreed that it was the thermostat, even though my mechanic said it wasn't... Anyway, I still haven't changed it and it still takes longer to warm up and will decrease in cool weather...... am I hurting anything by driving it like this? Is it running richer and clogging my O2 sensors? Am I getting worse gas mileage? (probably).. I just want to be sure that nothing is being damaged.... thanks in advance....


Todd Arnold
Todd, I have been experiencing longer warm up times and cooler running temps also. Our temps here in S. Florida have been in the 40's at night and haven't broken into the 70's for a while, and the humidity has been lower too. All of this adds up to cooler running temps and more horsepower. I wouldn't worry too much, it's much better to have cooler temps and high oil pressure.
As you mentioned, we discussed this in an earlier post. I suggested you check your temperature sensor on the engine just to be sure.

Nevertheless, if you are convinced that your thermostat is stuck open, I would get it fixed. You are not running the engine at a constant temperature. Although this is unlikely to cause anything to "break," emissions will be affected, particularly through the cat converter. Low temps on the cat will cause premature failure because of corrosion.

It's an easy fix, why not take care of it?
Hey Todd I'm kinda new and don't check post on a regular basis.I think I can be of assistance if you don't mind going through it again. Basically it seems you've come to an conclusion...Thermostat stuck open.
The NSX has 2 water temp. sending units on the engine.The(2wire) one mounted directly on the thermostat housing cover associates with the fans for the radiator and ecu. mounted just beind is the(1wire)sender which has a YEL/GRN wire attached to it.This sender is only for the temp. gauge and doesn't effect any ECU functions or the cooling system,just the temp.gauge.With that in mind I need to know if your fans ever turn on,and when.When you say "temp gauge going down..."Does the gauge at first warm to normal position the go down as you drive or gauge doesn't get as warm,or gauge doesn't move from cold.Also are you saying your car is cold because the gauge says so or because engine feel cold to the touch.
If fans come, on engine is hot,so I would check (1wire)sender.This is very easy to check....
1)check #5 fuse under-dash fuse box.IF OK go to next step.
2)disconnect YEL/GRN wire from sender and with another piece of wire attach to YEL/GRN wire and ground it.
3)now sit car and turn ignition on, while watching gauge,which should be sweeping to "H" mark.TURN OFF IGNITION BEFORE NEEDLE REACHES "H"
If gauge moves then sending unit probably bad Remember I don't know what was previously discussed,forgive me if your beyond this point.Though even if you had taken the Thermostat out, the motor should still get hot,to me stuck Thermostat isn't the problem.
Well I hope I was able to shed a little light .
hanks for the help Bruce.....The car does heat up while sitting and will reach normal operating temp. When I start driving, the needle slowly decreases....all the way to cold if i don't stop at a light or something, in which case it will warm back up... This is ONLY happening when it is cool out, so this is why it's the thermostat (IMO) During warmer weather (which is every other day) the car warms up fine and stays at op. temp. as normal..... Thanks again, was just wondering if I was damaging anything by waiting...Thanks for the info on the cats, NSXMAN....

Get it changed. Most wear that occurs in an engine is due to it being cold. When the oil in an engine is up to temperature there is virtually no wear on bearing surfaces, etc. Franky, it is not OK to leave it, unless in 50-60,000 miles you want to insure you need a new $12,000 engine. Based on the thermostat costing probably less them $100 to replace, it is an obvious choice. CHANGE IT!!!!!

Again, I had the same exact problem. Running the heater will also assure you that the engine really is not warming, not a sending unit or wire failure. The part cost me 40 bucks, with gasket, and it took about an hour to fix--once you remove the air cleaner, you can get to the thermostat easily. Just take note on the direction as you replace to make sure you get the new one in right. I suspect you and I are not the only ones to have this? Two in FL? Any A/C problems yet?
No, a/c probs except that the blower sometimes only blows on high (TSB).... My only problem with changing it myself is the bleeding of the system afterwards which seems to be incredibly difficult by the looks of the service manual.... So, I can dare try it... Thanks, I'll get it done soon. They are quoting me $190 to replace.