I'd check on your coolant temp sensor on the outlet flange that's above your upper radiator hose. Usually the connector is green. When my temps dropped on the highway, it was because the sensor was basically broken in half by the time I'd unfastened it.

(Image taken from user Kingdom934)

 

I'd check on your coolant temp sensor on the outlet flange that's above your upper radiator hose. Usually the connector is green. When my temps dropped on the highway, it was because the sensor was basically broken in half by the time I'd unfastened it.
View attachment 406011

(Image taken from user Kingdom934)

Thanks, did you ever find out why the sensor only malfunctioned on the highway though? Seems very strange

 

Thermostat stuck open

Sent from my SM-G981U1 using Tapatalk

 

Pretty classic sign of a Thermostat issue / partially stuck open thermostat.

Better to get addressed sooner vs. later - running the engine "cold" for extended amounts of time will not allow the motor to boil off condensation: which leads to the formation of carbon / sludge buildup in the motor.

 

Pretty classic sign of a Thermostat issue / partially stuck open thermostat.

Better to get addressed sooner vs. later - running the engine "cold" for extended amounts of time will not allow the motor to boil off condensation: which leads to the formation of carbon / sludge buildup in the motor.

Thanks, but wouldn’t the thermostat always be open anyway when driving for a whole hour or so on the highway? Or does the engine not get so hot that the thermostat needs to be open?

 

It depends, entirely on coolant temp.

The thermostat has a set opening temperature, once the coolant exceeds that temp, it melts the wax charge puck in the thermostat, causing the wax to expand, and -> opens the main valve, causing coolant to flow from the engine block -> to the radiator. Once the coolant circulates through the radiator / the coolant cools down, it returns to the system, lowering the coolant temp. Once the coolant temp is low enough, the wax in the thermostat charge puck cools, in-turn contracting and <- closing the thermostat main valve.

This heating / cooling action of the thermostat's charge puck is what "regulates" the overall coolant temp. in the system.

Coolant temp. is also largely regulated on coolant flow through the system -> to the radiator: which reduces temp. by passing air through the radiator.

How much the temp. is reduced by coolant passing through the radiator is dependent on outside (ambient) air temp., if the vehicle is moving, and the surface area (size) of the radiator installed in the vehicle.

On a moving vehicle at typical highway speeds, it may be as much as 40 degrees or more: again depending on outside air temp.

On a sitting vehicle w/ motor running, there is little cooling. This is why the vehicle has cooling fans: which turn on when the coolant temp. reaches a certain amount, to induce airflow thru the radiator -> and reduce the temp of the coolant.

A failed / stuck-open thermostat will consistently cause the motor to "run cold", and not reach proper operating temp.

 

@CamryFL , you should remove that first video as it is useless and totally backwards with reality; plus you are confused also--lower temperature coolant flows FROM the radiator to the thermostat to cool the engine.

...
The thermostat has a set opening temperature, once the coolant exceeds that temp, it melts the wax charge puck in the thermostat, causing the wax to expand, and -> opens the main valve, causing coolant to flow from the engine block -> to the radiator.

A failed / stuck-open thermostat will consistently cause the motor to "run cold", and not reach proper operating temp.

The bolded is where you are confused about the direction of flow thru a thermostat, likely from that first video.

A radiator works by cooling from hot at the top inlet to cool at the bottom outlet.

Think about it, the stuck open thermostat is letting cold coolant in all the time with no regulation--that is why the engine is running colder.

 

@Raptor178 @CamryFL Thanks for this - so it seems there are number of water temp sensors involved, one for the ECU, the gauge cluster, and possibly two others for the fans. I'm having a hard time seeing which is which - @Raptor178 could you tell me which sensor you replaced? I see two options on RockAuto, shown below. Were you on a V6? If so where on the engine was the sensor? Thanks again

https://smile.amazon.com/dp/B00FYIRT20?psc=1&ref=ppx_yo2ov_dt_b_product_details

https://smile.amazon.com/gp/product/B000CB23WA/ref=ox_sc_saved_image_1?smid=ATVPDKIKX0DER&psc=1

 

@Raptor178 @CamryFL Thanks for this - so it seems there are number of water temp sensors involved, one for the ECU, the gauge cluster, and possibly two others for the fans. I'm having a hard time seeing which is which - @Raptor178 could you tell me which sensor you replaced? I see two options on RockAuto, shown below. Were you on a V6? If so where on the engine was the sensor? Thanks again

https://smile.amazon.com/dp/B00FYIRT20?psc=1&ref=ppx_yo2ov_dt_b_product_details

View attachment 406074

https://smile.amazon.com/gp/product/B000CB23WA/ref=ox_sc_saved_image_1?smid=ATVPDKIKX0DER&psc=1

View attachment 406075

I have the 5S, the four cylinder.
I used what looks like the first pic you provided

1997 TOYOTA CAMRY 2.2L L4 Temperature Sender / Sensor | Shop Now at RockAuto

Cooling System Parts and More for Your 1997 TOYOTA CAMRY at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.

www.rockauto.com

Look for the 2 pin connector, where the sensor housing is very thin.

 

OP,
Had the same issue with a Ford van once. New thermostat was the fix. FWIW YMMV

 

Maybe you didn't realize it, but in a camry, the hose from the cool bottom section of the radiator is routed to the "inlet" pipe of the thermostat housing in the block. So chilled coolant flows from the radiator to the BLOCK.

The upper hose is the outlet from the pipe in the HEAD to the top of the radiator. Hot fluid flows from the head to the radiator.

The first video is incorrect for a camry, so it is confusing and has no place on a camry forum here.

 

A worn thermostat seems the most likely cause but maybe it could be a bad sensor. To know for sure what is wrong aim a temp gun on the coolant pipe right next to the sensor to see if it is the problem. I have had old thermostats lose some spring tension and open early causing a cold engine and I have also had the gauge temp sensor go bad. The temp gun will tell you which it is.

 

@numberforty1 , do you have a scan tool?
If you have one, there are more than one engine coolant temp sensors on your engine; you can compare the ECT sensor reading with what is shown by the gauge. After all, gauge sensor can go bad too, and even the gauge itself.
Furthermore,if the thermostat is having issue, the engine might stay in high idle longer than usual.
Just saying!