[R2D2]

Just to share with you guys some "best practices" I honed in over 38 years of driving (and riding bikes).

a) Get that cooling system checked regularly at the annual service. Just do it!
b) Some DIYs are encouraged by manufacturers related to topping off of critical fluids. The process of visual inspection of the expansion tank takes seconds. Don't be lazy!
c) Use OEM coolant preferably the premixed kind or use the approved concentrate with distilled or de-ionised water only. Use filtered drinking water in an emergency and then drain and refill with approved coolant.
d) Coolant flush every 3 years is ideal. A coolant flush, always with my car's OEM coolant is some 800-1000 bucks at the ASC with labour, a pittance compared to what I'd have to pay for engine or coolant system repairs.
e) Do you rely on your oil pressure sensor to warn you of low oil levels? No? I thought so. Similarly do NOT rely on the temp sensor to warn you of leaks or incorrect operation of the coolant system. Regular visual inspection is best. Each sensor does the job it is designed to do and will only do just that.

[NPV]

Amazing coincidence and timing of this thread - just a few days ago, we experienced something similar when on a vacation to Shillong and Cherrapunji. We had hired a Swift Dzire cab and on Day 1 of the trip we were returning from Krang shuri falls in the evening. About 20km before Shillong, we heard a whining sound and I suspected a bad wheel bearing but it went away after 2-3 bends on the hill road. The driver suddenly said "meter upar ja raha hai" and stopped the car. He meant that the temperature gauge was showing unusually high temperature. He spoke to couple of his driver friends on phone and then filled up about 6 bottles of bottled drinking water after which the temperature went down, but it would again go up beyond the half way mark while driving uphill on the ghat road, so at the next town enroute I asked him to stop at an automobile spares shop to buy coolant.

In the meantime, I had reached out to DBhpian and friend @nkrishnap and he suspected that the engine thermostat valve would have gone kaput, he advised me to get coolant filled up first and then head to the service centre. We then headed to a local garage and also bought distilled water at a petrol bunk nearby. After draining out the coolant reservoir that was filled up with drinking water earlier, we had the TVS Green coolant-distilled water mixture of about 6 litres in 1:4 ratio filled up and then he kept the engine on for several minutes before we moved on. It was fine after that and we reached our hotel after an hour.

Not wanting to take a chance, the driver headed back to Guwahati to get his car checked and fixed at a Maruti authorised service centre the next day and the cab agency sent us another driver next morning for our trip.

Next day, the cab driver called me to inform that the car was fixed by replacing the thermostat valve and the water pump.

Big shoutout to @nkrishnap for the timely remote guidance and help

[Sanjeev V S]

Hello Friends,

A few weeks back in early April 2022 while driving from Bangalore to Palakkad, Kerala just near Chandra Nagar Circle ( entrance to Palakkad from NH) my AC started blowing hot air instead of cold air and immediately my temperature gauge ( Thermometer icon) on my dashboard of my 2014 Wagon R Vxi started flashing, I knew something is wrong, switched off AC and literally crept till my hotel in less than 20 kms speed.

Reached Hotel parked, opened the bonnet, and visually saw the coolant reservoir had coolant between the 2 markings, I did not open the radiator cap as I knew it would be very hot. I called my FNG owner in Bangalore, he told me it could be a fuse, a relay or the radiator fan failure if the radiator has not leaked. There is NO leak.

The next day on Sunday morning called Indus Motors (ASC in Palakkad) they came in an hour checked the fuses, relay and said the radiator fan has to be replaced.

Again I drove to Indus Motors, they had kept a bay with parts ready, the car was raised in the ramp, coolant drained, old fan removed checked, new fan fitted, coolant filtered and refilled, coolant topped up, road tested, I drove back to Bangalore non-stop no issues. With less than 4,000 Rs including a new radiator fan, labour and Roadside assistance I drove back with no issues.

Thanks to Maruti, Indus Motors Palakkaad

Sanjeev

[GForceEnjoyer]

Originally Posted by Shreyans_Jain

Again, it has been a case of the car running out of coolant, overheating and showing no indication of any kind.

Something I've noticed on both our cars is that the coolant temperature gauge always stays in the dead centre regardless of driving style and ambient temperature. I had previously attributed this to modern cooling systems being insanely good, but what the gauge tells you isn't exactly true.

The coolant temperature isn't maintained at 90°C all the time as the gauge would have you believe. In all cars with electronic sensors, it is programmed to not move as long as the temperature is within a suitable range, and only move into the red zone if it gets dangerously high. This was supposedly done to stop owners bringing their cars in to the dealership because the needle moved a touch over the centre on a hot day and/or after a hard run, and they thought something was wrong. The downside of this is that there is a lot less warning to be had in case there is genuinely something wrong.

This is the most likely cause of your cars' gauges not showing a high temperature. The consolation here would be that you clearly did a good job of keeping the temperature from reaching dangerous levels through your careful driving style and timely and frequent addition of water.

[Dhillon]

Originally Posted by sarav100

My 2012 Figo diesel did not have any temperature gauge either but it had a temperature warning light that I know worked and it also had a digital temperature display that works only in a special diagnostic mode.

The radiator fan stopped working twice in it’s 7th ownership year / ~80K kilometres. During both the instances, temperature warning light worked and I driving at a consistent speed of 60kmph in 6th gear.

I also owned a 2010 Petrol Figo. My car showed temperature warning light and I immediately noticed that there is no coolant in the car. Coolant leak was diagnosed to a very small hole in the coolant box.
OT, but I guess Figo had 5 gears

Originally Posted by sarav100

During both instances, issue was diagnosed as blown fuse. As per mechanic, apparently the radiator fan runs a bit rough and it blows the fuse due to higher load.

First gen Figo was notorious for this. Every time I switched on the AC, the fan would start at 2nd speed which was very noisy (1st one was much lower) I also faced this twice at about 90K KMs.

[sarav100]

Originally Posted by Dhillon

OT, but I guess Figo had 5 gears

You’re absolutely right. Figo has 5 forward gears. I got the gear count confused with Creta.

[itsbaman]

I faced a coolant leakage issue on Skoda Rapid back in September 2021 due to a faulty coolant elbow. It was a very minimal leakage issue, but luckily car gave the warning well in advance and I happened to be in Chandigarh. I couldn't get the coolant elbow replaced at that time due to the non-availability of the same. So I topped up the coolant and bought a 01-litre spare coolant bottle in case of an emergency as I couldn't leave the car in the workshop for 07-10 days. It drove without any further issue as I got the replacement done after 15 days. It cost me around 8200.

[COMMUTER]

My 2016 Figo 1.5 D too faced heating issue. Initially, it was used exclusively for night run alone and a few horns blocking the cooler wasnt adverse. Now, it just crossed 1.3L kms. The driving usually takes place at day and I noticed the engine bay to be noticeably hotter. I had removed all the horns obstructing airflow now and had mounted two single pipe horns away without affecting cooling.

[venkyhere]

Originally Posted by GForceEnjoyer

The coolant temperature isn't maintained at 90°C all the time as the gauge would have you believe. In all cars with electronic sensors, it is programmed to not move as long as the temperature is within a suitable range, and only move into the red zone if it gets dangerously high. This was supposedly done to stop owners bringing their cars in to the dealership because the needle moved a touch over the centre on a hot day and/or after a hard run, and they thought something was wrong. The downside of this is that there is a lot less warning to be had in case there is genuinely something wrong.

Let me humbly disagree.

For a 90C the hysterisis window is going to be +/- 1 degree or 2 degrees, so guage will sit nailed to the middle only between 88-92 or between 89-91.

Otherwise, it will faithfully move. Plus the guages are non-linear with higher sensitivity the further the temp is beyond this hysterisis window; ie, say the guage is linear from 91-94 and then be extremely non-linear beyond that (say from 94 to 97 it will sweep more of the guage than from 91 to 94) - it is designed to increase the level of "threat" to the driver progressively as the temp gets further hotter than ideal.

Hence, if there is a guage, it will be surely better than having a 'warning lamp only' (which is the feature that aligns with your statement of driver getting warned only when things have escalated too much).

In OP's case, the problem is totally different - for ECT to throw up a warning, there has to be C in the first place. No coolant, the sensor is worthless. Perhaps carmakers should consdier embedding a tiny flowmeter within one of the bigger coolant pipes and provide a "coolant less/empty" warning.

[CommitTran]

Originally Posted by NPV

In the meantime, I had reached out to DBhpian and friend @nkrishnap and he suspected that the engine thermostat valve would have gone kaput, he advised me to get coolant filled up first and then head to the service centre. We then headed to a local garage and also bought distilled water at a petrol bunk nearby. After draining out the coolant reservoir that was filled up with drinking water earlier, we had the TVS Green coolant-distilled water mixture of about 6 litres in 1:4 ratio filled up and then he kept the engine on for several minutes before we moved on. It was fine after that and we reached our hotel after an hour.

Not wanting to take a chance, the driver headed back to Guwahati to get his car checked and fixed at a Maruti authorised service centre the next day and the cab agency sent us another driver next morning for our trip.

I faced same issue in my 1.3 Lakh kilometer used Ertiga diesel. As mentioned in the starting post of this thread I got no prior warning or anything suspicious happened. Car was happily munching miles and all of a sudden the AC stopped cooling which made me check my temperature gauge which was at high. Luckily I was in a service lane and not on Highway so I immediately turned off my car and waited for 20 mins or so. After that I filled it up with water and took it to the nearest Maruti garage which was 7 mins away. This time around the temperature stayed normal as drive was short.
Thermostat valve was the main culprit along with slight leakage of coolent which is still to be identified. Leakage is so slight that if I keep my car stationed at same place for 48 hours I may get 3-4 drops of coolant. I'll be taking it to an expert soon. Till then I am enjoying the habit of checking coolant levels every other day and topping it up if needed.

[Swapnil4585]

The temperature needle on the dashboard isn't the only thing one must rely on.

I have developed a habit, in addition to inspecting the engine bay periodically, and that is to connect Torque Pro while driving and keep checking the temperature after some time.

An hour or more of high-speed drive with AC on, the app shows 86 degrees. Similarly in the blistering hot bumper to bumper traffic, it stays in the 92-96 degrees range.

At times I go overboard by inspecting the engine bay in the middle of a highway trip if I had to drive on a patch of under construction / potholed / gravel filled road.

[GForceEnjoyer]

Originally Posted by venkyhere

In OP's case, the problem is totally different - for ECT to throw up a warning, there has to be C in the first place. No coolant, the sensor is worthless.

Thanks for clarifying that, I stand corrected.

This is a little off-topic but I've seen a different reading on the gauge vs the menu that can be accessed by long pressing the odometer stock while simultaneously turning the key (2006 Ford Fiesta). You can find a post on Team-BHP about the same here. https://www.team-bhp.com/forum/long-...ml#post3930507 (My 2015 Ford Classic 1.6 Titanium) You can see the needle sitting at 90°C whereas the display shows 102°C (this is with coolant present in the reservoir). Perhaps this is peculiar to this model?

[JP_800]

I too came across such an incident here in the UAE. My friend's Figo sedan overheated and blew the head gasket. He was driving with family and noticed low cooling of A/C. BTW, Figo doesn't have a temperature guage and he didn't attribute the A/C cooling issue to the engine overheating. The warning light did not come on untill then. He kept driving ON , without A/C . After a km or so the engine overheat warning came on. He immediatley stopped the vehicle and opened the hood to see the coolant reservoir empty. The car was towed to the
independent workshop. They diagnosed the complaint to a faulty thermostat leading to overheat. But the head gasket too has failed consequentially.

Fortunately my friend had bought the car used from CARS24 and was covered under warranty. He had driven barely 600 kms ( the car had 91,000 kms on the od when he bought it). Intially CARS24 rejected warranty, but later agreed when my friend raised a complaint with the Economic department. So zero costs of repair for him, but downtime of 2weeks.

Had there been a temperature gauge, he could have guessed that the A/C low cooling was due to the compressor cutting of because of engine overheat.

Another thing, Aluminum engines are so sensitive to overheat compared to cast iron engines. I've seen lot of examples, especially Chinese engines (SAIC NLE2.0) failing head gaskets due to minor overheat issues.

[SS-Traveller]

Originally Posted by Shreyans_Jain

It was standard practice to stop to let the engine cool down after a few hours on the road, top up the water and then drive on. Fortunately, modern cars have become a lot more reliable and tolerant to heat.
...
Observations over the past week

• The engine overheat warning lamp has never lit up.
• The AC has been functioning normally. Cooling is proper, even when idling for 5-10 minutes while waiting. It has never tripped.
• Car has shown no sign or indication of overheating whatsoever. It has felt, smelt and driven just like at any other time.

Again, it has been a case of the car running out of coolant, overheating and showing no indication of any kind.

In the days of the Ambassador and Fiat, the coolant system was usually not pressurized (the rubber gasket of the radiator cap was invariably removed), did not use coolant (just tap water sufficed, though some of us used distilled water), and did not use a thermostat valve to control the circulation (there used to be a valve, which was removed at the first opportunity by most mechanics). This meant that the circulating coolant fluid (plain water) would run in an open system, and would boil if part of the water leaked out or the engine was overheating for some reason, and the conversion from liquid to steam would carry some of the heat (latent heat) away - until all the water boiled off, and the temperature gauge would rise to the red zone. Before that could happen, it was standard practice to stop the car and add some more water to top up the radiator.

The temperature gauge was (and is) placed into the bottom tank of the radiator - the coolest part of the system. When the water boiled, there was a slight rise of the temperature gauge needle, until all the water evaporated, when the needle would suddenly shoot all the way to the 'H' end of the gauge.

Then came pressurized cooling systems, with the coolant not being allowed to boil & evaporate. At roughly 15 psi (which is the pressure that the pressure cap of the radiator holds), the boiling point of the coolant rises to ~125 degrees C. Any little evaporation that happens, is allowed to be redirected to the expansion tank, where it can condense back to coolant. In any case, coolant at atmospheric pressure boils at over 106 degrees C.

So, if this closed loop cooling system is intact (no loss of coolant or pressure), the temperature can well rise far enough to be detectable on the temperature gauge, such as in case of a failed cooling fan (the commonest occurrence) or a broken V-belt (water pump not running = no circulation of coolant = no heat exchange) or a thermostat valve that is jammed close. One may notice that the coolant level in the expansion tank has risen more than the 'High' mark, or even overflowed a bit.

However, if the coolant is leaking out (e.g. broken hose, punctured radiator), the coolant pump will continue to circulate the remaining coolant, until there is too little of it to circulate (level below the radiator bottom hose, so the coolant pump cannot suck it up). There is no more coolant to remove the heat from the engine block, while the bottom tank has residual coolant that cools down due to the airflow below the car - ergo, the temperature gauge remains in the normal zone, or even shows a drop in temperature. However, the engine continues to overheat until it blows a gasket (or worse).

As the engine overheats due to loss of coolant, the electronics kick in. In old cars, the usual giveaway of an overheating engine was the knocking (pre-ignition) sound on accelerating - modern fuel injected ECM-equipped engines have knock sensors that dynamically alter the ignition timing and / or the fuel injection timing and quantity, effectively countering the pre-ignition, so the driver fails to realize there is something wrong. This is until the overheating protection system turns the AC compressor off (intermittently at first, then completely), and then tries to reduce power to the engine, which is when the driver senses something is wrong.

Therefore, the best indicator to immediately check for coolant loss due to leakage is when the AC is suddenly not cooling optimally, and the car seems to have lost some power / acceleration. Opening the bonnet might or might not show where the leak is, but the smell of coolant vapour is often present (either releasing as steam from the leak point, or evaporating after coming in contact with the hot engine block). The temperature gauge is not going to tell you anything until it is too late.

Edit:

We were parked in Devprayag having lunch when I detected a little whiff of the smell of coolant from the car. I checked but nothing was apparantly amiss.

This can be explained by the phenomenon of heat soak. Once the hot engine is stopped (hotter than normal because of low coolant), it tends to boil the coolant present in the cooling gallery around the block (remember, the system is not fully pressurized any more because of the leak, so coolant will now boil at a lower temperature, and come out as steam through the leak). The coolant vapour has a typical odour, which is what you must have smelt - but saw no trace of coolant on the ground.

[rrs1951]

Reminds me of my Premier Padmini which I used to drive back in the nineties. Failure of radiator hoses was a frequent phenomenon, and I used to carry a full set of radiator hoses and hose clips in the boot. I had become pretty good at replacing those, too!

I always expected the temperature gauge needle to move upward in case of a leak in the radiator hose. However, that never happened; on the contrary, the needle would move down, indicating a lower than normal temperature. Later, I discovered why. Normally, the thermocouple would be in contact with the water in the radiator, and would show the correct temperature. But when the hose ruptured, water would come out of the ruptured hose, and there would be no water flow over the thermocouple. The problem was the location of the thermocouple.

As has been rightly pointed out, the indicators will come on only if they are able to sense the temperature - in other words, there is a coolant flow (or water flow, in the case of my Padmini) over the thermocouple.