Low coolant/engine temperature

[TigerNSX]

I went for a drive in the morning (temp. around low 30s) - mostly gentle, highway cruising for about an hour or so. And the coolant/engine temperature gauge on top left corner of the instrument panel would barely move up (stuck at low temp). No check engine light. The car idles fine. Coolant was flushed about 3-4K miles ago at the time of the T/W service. I also noticed that the temp would slowly climb up (not much, but slightly more) when I am stopped at the traffic lights, but would go down again once I started cruising on the highway.

Is this normal? Could it be due to the chilly air?

 

[Miner]

It sounds like the thermostat is stuck open.

My NSX takes a few miles to warm up on a cold morning, but once warm it will usually stay warm. I will caveat that I’m in the southern half of the country.

If you were running the heater it would reduce the coolant temp a bit as well, but the car should warm up and stay at normal operating temp.

How long have you had the car? Is this your first winter? After flushing of the coolant, had it been warming up normally until now?

 

[goldNSX]

Simple check:
- open the front hood
- touch both coolant hoses to the radiator
- if both are about equal AND the temp is low
-> stuck open thermostat

 

[Old Guy]

I am going to jump on the thermostat bandwagon as the likely cause.

If you have one of those IR non contact thermometers, the quick test would be to take a measurement of the outside of the thermostat housing. The thermostat is supposed to start opening at 76 - 80 C and be fully open at 90C. If after driving around for a while the housing temperature is below 76C you probably have a stuck open thermostat. GoldNSX's method works if you have a good 'feel' for temperature. I don't. Both 70C and 90C just feel hot.

If the thermostat housing temperature is coming up into the 90 C region and your gauge is still reading cold, then you need to go through the test procedure in the service manual to determine if the problem is the gauge or the sensor (1998 models still use a dedicated sensor).

 

[Kaz-kzukNA1]

With many NSX that had stuck open thermostat, it took ages reaching the normal temperature even after start driving but eventually, all of them displayed the normal temperature on the gauge.
Unless you are using the custom made aftermarket radiator or having major cooling system issue (low coolant), I would think your NSX would follow the same.

You may still have the stuck open thermostat and most likely, multiple issues.

Same issue on several NSX including mine.

The cause was the sender unit on the water passage unless you have the later Acura US spec that doesn't have this sensor.

If you have multimeter, you can easily check it.

After driving for a while and fully warmed up (no longer in the fast idle region), park the car and stop the engine.
Keep IG Key in P0 Off position to prevent damaging the gauge unit.

Remove the single wire socket terminal from the sender unit.
The area is very hot so be careful.

Now measure the resistance between the sensor top and any nearby GND.

Should be just below/around 50ohm.
Yours is probably well over 100ohm.

If you have access to the resistor components, you can use it to check your gauge as well.

Kaz

 

[acuhon]

I went for a drive in the morning (temp. around low 30s) - mostly gentle, highway cruising for about an hour or so. And the coolant/engine temperature gauge on top left corner of the instrument panel would barely move up (stuck at low temp). No check engine light. The car idles fine. Coolant was flushed about 3-4K miles ago at the time of the T/W service. I also noticed that the temp would slowly climb up (not much, but slightly more) when I am stopped at the traffic lights, but would go down again once I started cruising on the highway.

Is this normal? Could it be due to the chilly air?

If your heater was working fine, than it's bad sender unit. If you couldn't get much of heat from you heater while driving in low 30s , than it's open thermostat.
I picked my 97 NSX in Oklahoma and driving home in low 30s the gauge didn't move much and I was freezing. After I covered 1/2 of radiator with plastic the gauge moved to it's regular spot (one tick under 1/2) and heat started to work.

 

[TigerNSX]

Thank you so much for all of your inputs and help. I will go over your points and address the issue. It does sound like a stuck thermostat because the heater is only blowing lukewarm air even at the highest temperature setting.

Really appreciate your time and help.