[GTO]

Originally Posted by rr_zen

While the usual concern would be what if the temp gauge shows a lower temp than normal, my concern is how would I even identify this phenomenon in cars that do not have a temp gauge.

Which is why 93% of BHPians want the temperature gauge back on all cars - Link.

Every engine has an 'optimum' temperature that it performs best at. The OP probably wouldn't have realised that he had a problem, if it weren't for the gauge.

[arunphilip]

Originally Posted by rr_zen

Interesting thread. While the usual concern would be what if the temp gauge shows a lower temp than normal, my concern is how would I even identify this phenomenon in cars that do not have a temp gauge. For eg, the A-Star

Originally Posted by Jeroen

The short answer is you wouldn't, unfortunately. You can take your own temperature readings now and then, with for instance a Infra red thermomenter, but its not very practical and you would take a considerable number of readings to figure out if anything is wrong.

Some cars expose the coolant temperature via one of the sensors readable by OBD-II. That'll give you insight into how the coolant temperature rises upon startup until the thermostat opens the flow into the radiator, at which point it will stabilize (or fluctuate as the high-speed cooling fan comes on and off).

Here again, as Jeroen has mentioned, you'd need to have a baseline to compare against (or the experience to get by without a baseline), when you know things were working normally and correctly to realize something is now amiss.

[Abhi_abarth]

Originally Posted by Jeroen

Check what the manual says. This looks a little low to me.
Jeroen

Not able to embed the image due to poor quality hence typing the text :

'Under normal conditions, the needle may hover around the scale according to the car use and engine cooling system management that the system self adjusts continually, but it should always remain out of the red danger section'.

[SnS_12]

Well, in my 2008 Indica Xeta petrol I have noticed that when I used to run the car without the air-condition the temperature gauge would reach the halfway mark and when I switch on the air-condition it would stay at quarter. Never really applied my mind why this used to happen as the car was running normally otherwise. But, now I would be interested to know if anyone else has faced this issue and the reason for the same? As, Jeroen said running below idle operating temperature would also damage engine internals. So now I don't know what was the ideal engine running temperature in my Indica, which by the way has been sold off now.

[vikram_d]

Originally Posted by GTO

Which is why 93% of BHPians want the temperature gauge back on all cars - Link.

Most cars which don't have a temperature gauge normally come with two temperature based warning lights on the instrument console. One for high temperature and one for low temperature and if the engine temperature goes dangerously low the low temperature light along with CEL will come on.

[thedragula]

As everyone has pointed out, this could be the thermostat valve going bad. However, the thermostat valve only regulates the flow of coolant to the radiator. i.e., if it gets too hot, some coolant is diverted from the engine circulation to the radiator after which the cooled liquid returns to the engine lines to cool down the engine. If the coolant valve has gone bust, while your temperature will remain low, it will also fluctuate, especially in cases where the car is stationary due to which the radiator becomes less effective.

If the temperature is low and is at a constant, you need to check the radiator cooling fan. The relay which controls the fan itself or the relay which regulates the speed of the fan must have gone bad. In such a case, the fan runs continuously without stopping once the coolant has cooled down below ~85 degrees.

Before you open up the thermostat valve, do a visual check on the fan and the frequency and speed of operation.

[jfxavier]

Originally Posted by arunphilip

Some cars expose the coolant temperature via one of the sensors readable by OBD-II. That'll give you insight into how the coolant temperature rises upon startup until the thermostat opens the flow into the radiator, at which point it will stabilize (or fluctuate as the high-speed cooling fan comes on and off).

Here again, as Jeroen has mentioned, you'd need to have a baseline to compare against (or the experience to get by without a baseline), when you know things were working normally and correctly to realize something is now amiss.

Originally Posted by vikram_d

Most cars which don't have a temperature gauge normally come with two temperature based warning lights on the instrument console. One for high temperature and one for low temperature and if the engine temperature goes dangerously low the low temperature light along with CEL will come on.

I have seen that the coolant temp of my car is around 90 deg C. This info is from the ECU via the OBDII adaptor and Torque app.
With less and less raw data available to the driver, these adaptors are the only source of information.
You will quite like the amount of information that the ECU can provide if you get the OBDII adaptor & app.

[Jeroen]

On most cars with a temperature gauge you can actually 'see' if the thermostat works correctly. If you start from cold and start driving you will see the temperature rising. The minute the thermostat opens you can see a small, but noticeable, drop in the temperature reading. Once the thermostat is open it will start regulating smoothly, but the initial opening is often noticeable.
Jeroen

[aniketi]

Originally Posted by anish5225

Hi,
I have been noticing something strange with the engine temperature on my 2009 Optra Magnum Diesel run 70000 KMs. In the past, after diving for ~ 10 mins, the temp gauge used to reach the halfway mark and stay there for as long as i drive.Then on, it will not go above or below this point no matter how long or how hard I drive.

But since the past few weeks, the temperature gauge hardly touches the earlier settling point even if I drive for an hour or two. Only reaches about midway. If I use the AC, the temperature drops a few notches further. Any idea what could be wrong?

Thank You
Anish

Exactly same problem I observed in my brothers Indigo Petrol. Temprature guage shows well below half way mark and it stays there only. If we put AC on, it goes down further. This is happening for last more than 2-3 years now. When I asked my brother about it, his reply was its like that only. He has bought Indigo in resale 5 years back. No problem faced till date. My brother is person who don't spend anything unless its obsolutely needed or its stalling the car

[parth.jain]

I have always believed that one of the functions of the thermostat is to switch on the radiator fan. Usually, cars with single radiator fan has a 'double' speed fan. When the car gets heated up the fan runs on normal speed and when the ac is turned on, it runs on a higher speed.
You can check if the radiator fan starts as soon as the car is started but air con is switched off, if yes, then something is definitely wrong!

I hope I am not wrong.

[Jeroen]

Originally Posted by parth.jain

I have always believed that one of the functions of the thermostat is to switch on the radiator fan. Usually, cars with single radiator fan has a 'double' speed fan. When the car gets heated up the fan runs on normal speed and when the ac is turned on, it runs on a higher speed.
You can check if the radiator fan starts as soon as the car is started but air con is switched off, if yes, then something is definitely wrong!

I hope I am not wrong.

Couple of thoughts. In the context of this discussion thermostat has been used as meaning the thermostatic valve in the cooling liquid. I.e. A mechanical three way valve that opens and closes based on temperature.

What you mention is a thermostatic electrical switch that switches, based on temperature, the fan. Sometimes you might find that the fan uses a special kind of coupling which responds to the air temperature blowing through the radiator. So it's not electrically controlled but thermostatically. You will find these on some older Mercedes. And some cars/engines have the fan permanently driven, so in that case the thermostatic valve does all the work so to speak.
Jeroen

[Jeroen]

To add, on my Alfa Romeo Spider the normal cooling fan is permanently driven via a V-belt from the pully on the crank. So its the thermostatic valve in the cooling circuit that controls the temperature ( and by the way is a weak spot as I have replaced it numerous times). But it also has an additional, second, electrically driven fan, in case you switch on the AC. This second fan is electrically driven and also has an thermostatic electrical switch. So there are quite a few different set ups of thermostats (mechnical, electrical), fans and system lay outs about.

Jeroen

[jfxavier]

Normally a thermostatic valve is bypassing the coolant and as the temp. increases the sealed cartridge expands and moves the valve spindle against the spring (which keeps it in the bypass position) and lets the coolant go through the cooler/ radiator. If you find that the valve is stuck in the "open to cooler" position, it might be possible that it is stuck due to some solids coming in between the moving parts and it just needs cleaning up. Maybe you can check the coolant quality and flush/ replace the coolant if you find that the coolant is contaminated/ dirty. In that case, you might want to check for the source of contamination as well.
Normally the valves get stuck in the "bypass" position. Very rare to see the valve stuck in the "open" position as there is a spring trying to close it. It might be possible that the spring is broken, but very rare as I said.

[IPathan]

Originally Posted by Abhi_abarth

Reading all the posts, I have started feeling scared as my palio S10's temp gauge always stays within the 1/4 mark

While driving a friends Palio 1.6 (1st owner of the vehicle) I noticed the temp was at 1/4 mark (engine was running for more than 1 hour), it seems it was this way from the day he took the delivery and he never had issues

[SreeT]

I agree with other bhpians that the coolant valve probably is at fault here. And in our Zen, the cooling fan runs continuously when the AC compressor is running, else it runs intermittently - almost only when the car is stationary. Maybe this is the reason why you are seeing lower temps when the AC is running.
I hope it's not a serious issue and is easily fixed!