[Shreyans_Jain]

There was once a time when going on a road trip meant topping up fluids the morning of the drive and always carrying a spare bottle of water for the trip, perhaps even a fan belt. 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. Cooling systems have evolved to the point where you can be stuck in bumper to bumper traffic in 50 degree summer heat and your car's performance or it's AC's cooling will not skip a beat. Most modern cars have in fact done away with the temperature gauge. All we get is a little warning light that is supposed to light up the off chance something goes wrong. But what happens when things actually do go wrong?

2022 has been the hottest summer on record. This year I have had two incidents of cooling systems failing, and the observations have been startling.

Tata Hexa, March 2022

This has been touched upon in my thread https://www.team-bhp.com/forum/techn...y-expired.html

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. There were many tempos, taxis and buses in vicinty, so I attributed the smell to any one of them. We loaded up and drove down towards Kaudiyala for our rafting session. At the meeting point, the rafting person who was waiting for us was the first to notice green liquid dripping from the car. Within moments, we had the automotive equivalent of a crime scene.

While the rest of the family went rafting, I tried to figure out a fix. Filled in jugs of water from a nearby dhaba. The radiator was totally empty, 5 jugs of water went in. I started the engine. Immediately, the point of failure became visible: green water and steam were gushing out of a hose. The hose was pretty deep inside the engine bay, visible but not accesible to hand. The only option was to top up the car every few km and drive on, hoping for the best.

Temperatures were still above 40 degrees. Those familiar with Rishikesh know how bad the traffic jam gets, in Shivpuri and in the bypass in the evening. Heat + bumper to bumper traffic + fully loaded car + no coolant, what could go wrong? Apparantly, very little! We stopped at Shivpuri for tea and snacks, so the car got a break to cool down. The water I had filled before was long gone, it took in another 5 liters. The leak was such that it would empty out in a few minutes. We stopped to refill just before Rishikesh, then once on the bypass, then after the bypass and then finally at our hotel in Haridwar. More or less at intervals of 30 minutes. Every time, the radiator would be totally empty and the car would take in 5-6 liters of water, while throwing out large amounts of steam as the water was poured in.

Critical point: When filling in water into the radiator of an overheated engine, always do so with the engine running.

The next morining, the car was taken to TASS Haridwar, which performed emergency repairs with MSeal. The damaged hose for later replaced at TASS Faridabad.

Observations from the day

• The temperature gauge stayed normal at all times during the ordeal. No error or warning of any kind popped up. Nothing.
• The car's behaviour remained perfectly normal. No sign of straining, nothing sounding different, no obvious steam coming out from anywhere while driving. Only when we stopped, opened the cap and added in water.
• I cant stand smoke, which was there in plenty in the traffic jam in Rishikesh. Hence, the AC was kept running thorughout. The cooling was totally fine. At no point did the AC trip.

Basically, the car gave no indication of overheating whatsoever. Had we not stopped in time and seen the coolant dripping before it had totally run dry, we would have simply remained oblivious. We were lucky, if it were too late, I would have been staring at a siezed engine.

Honda City, May 2022

My City (diesel) is in its 8th year and has done 175k km. It has exhibited perfect mechanical reliability thorughout with no out of the blue failures whatsoever.

Last week, me and my father went to Murthal for some work, and took the City. On our way back home, I took the Eastern Peripheral Expressway route. Cruise control was engaged at 100kmph all the way and the AC was on at full blast. My father had noticed that the engine sounded a bit loud. I had replied that he felt so because he was traveling in this car after a long time. Told him the drive also feels a little strained and it has been that way for some weeks now. My theory was that the engine is ageing and is past its prime. Basically, it was normal behaviour overall. It was raining off and on, and I had exhausted the windsheild washer fluid by the time we reached home.

Next morning, I popped up the hood to fill in water. I noticed a bit of green residue near the washer reservior's cap. As I looked more closely, I was horrified to see splattering of green all over the engine bay.

I checked the coolant reservior, it was empty. I opened the radiator's cap, it again was empty. I filled it up with water, and it took in more than 3 liters. The car's coolant circulation system had sprung up a leak somewhere and had totally emptied out. The car had been going about with no coolant since god knows when.

I rushed to my local Honda dealer, and they diagnosed it to a leaking hose. The damaged part wasn't in stock and I was told it would take a week to procure it. The car is our daily beater, and is being put through its everyday grind as always. In bumper to bumper local traffic in the current 45-47 degree heat. We just fill her up with water every morning and drive off. Every day, we find the radiator totally empty and the car takes in 3 to 4 liters of water. I will be taking the car to the dealer tomorrow for the hose replacement.

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 both cases, it was alertness, timely intervention on my part and sheer good luck that catastrophic damage to the engine was avoided. Why did any warning not show up? Even the ACs did not trip. That is usually the first and obvious sign of an overheating engine. Both Tata and Honda SAs had no answer.

It is my sincere advice to everyone whose cars have done more than 1lakh km or are more than 5 years old: Please get your radiator, water pump and all hoses inspected thoroughly every year. And do lift up the hood and take a good look at the engine bay every now and then. I have been fortunate. You never know when your luck runs out.

[Aditya]

Thread moved out from the Assembly Line. Thanks for sharing!

[vigsom]

Lucky escapes on both cars, Shreyas_Jain. I completely agree with you on the inspection part. In fact, such inspection should be performed when the car is tendered in for service. There will be a check point on inspection of the engine cooling system; however, who performs these checks diligently these days? The objective is just to bill, and handover a nicely polished car after service - that's all.

From what you've described, this looks like a failure of the radiator bottom hose on the Hexa; Honda City - looks to be the same.

Originally Posted by Shreyans_Jain

- 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.

As long as there is coolant circulating, and the ECT (Engine Coolant temperature) sensor measures the temperature to be normal, it will not trigger the overheat lamp OR trip the aircon.

1. Even if the radiator is, say, half full, the water pump would be provided adequate suction, and the coolant would circulate. The exchanger (radiator) is efficient, and with the fan in operation will continue to cool the coolant. The volume of coolant will gradually pick up more heat, and after a certain saturation, when the mix begins to boil, the temperature will begin to rise, and the gauge (if available) will show a rise in temperature. If the radiator runs dry, there will be no flow of coolant and the temperature sensor will not detect high temperature (have never experienced this situation in a car, but have seen enough of this in a manufacturing unit).
2. The only case when the temperature begins to go up rather rapidly is when there is a leak of combustion gases eg. head gasket leak
3. On a 2007 Honda Accord, I've seen that the engine shut down when the temperature went beyond a certain value (90% of range IIRC). This is the ultimate protection system for the engine, but not sure how many cars have this built in interlock
4. I would have allowed the car to cool for at least 30 minutes before adding water

Failure of hoses can be attributed to

a) ageing,
b) quality issues in the hoses,
c) quality of coolant,
d) malfunctioning pressure cap

I have a practice of opening the bonnet at least every week and checking

1. condition of both hoses on the radiator,
2. heater core hoses at the firewall,
3. coolant level in the expansion tank,
4. engine oil level,
5. power steering fluid level, and
6. after a drive, open the bonnet again and inspect the hoses for bulges, leaks.

[Shreyans_Jain]

Originally Posted by vigsom

As long as there is coolant circulating, and the ECT (Engine Coolant temperature) sensor measures the temperature to be normal, it will not trigger the overheat lamp OR trip the aircon.

Hexa’s total coolant capacity is 6 or 7 liters. City’s is 4.5. The amount of water each car took in tells me the all the coolant had leaked out in both cases. Both radiators had run dry. The cars were being driven in demanding conditions in summer heat.

I don’t see any reason for them to not show the overheating indication.

[Doge]

What really sucks is that a lot of cars don’t have a temperature gauge. I feel a temp gauge and an oil pressure gauge is a must on vehicles sold here. A warning lamp tells you when it’s too late, a gauge can warn you much before. I remember years ago I was driving a WagonR and noticed the gauge shooting up and eventually the car dying and then not starting. I waited for the gauge to cool down and then made the trip by pulling over whenever it got too hot and made it back.

[R2D2]

Originally Posted by Shreyans_Jain

The temperature gauge stayed normal at all times during the ordeal. No error or warning of any kind popped up. Nothing.

Those were close calls. You're lucky the leaks were discovered before damage was done.

The temp sensor needs to be immersed in coolant for it to read the temperature and transmit it to the dash. It's a fallacy to assume the dash warning light or temp gauge will function or provide a warning beep without coolant being present in the system.

As you rightly advised, checking the coolant system regularly is a must and more so during the summer.

PS - Call me old fashioned but I still follow the same age old routine of checking fluids i.e. coolant and brake fluid and sometimes engine oil before I drive and always before a long distance trip. Also, checking under the bonnet is a routine as cats and their kittens like to make a home under the hood. I really don't want to see a hurt or dead animal. They are so attached to my car that one kitten, some 6 months old, even lay down in there to breathe its last. Yeah, not kidding. It probably thought of the engine bay as the safest place and a refuge. Poor creature.

[sagarpadaki]

Now that you have corrected the cause of leak, do a radiator flush with liquimoly or whatever you like. The tap water you have used will definitely corrode the engine internals.

Also, after doing the flush and filling new coolant and using for a few hundred kms, replace the coolant once again. This will be a small price to pay for the long term peace of mind.

[Shreyans_Jain]

Originally Posted by R2D2

The temp sensor needs to be immersed in coolant for it to read the temperature and transmit it to the dash. It's a fallacy to assume the dash warning light or temp gauge will function or provide a warning beep without coolant being present in the system.

This is news to me. In our older cars, WagonR F10D and Scorpio 2.6DI, the temperature gauge used to always throw a fit at the slightest loss of coolant or overheating. And there were quite a few such instances over the 13 and 15 year ownerships of the cars respectively. We lost a few radiators due to dog hits during the Delhi-Mumbai night runs we used to do back then. The temperature gauges always did their job.

Going by your reasoning, normal temperature is the temperature of the coolant on a fully warmed up engine, which is about 90 degrees celsius. Now if the coolant empties out suddenly due to any reason, the temperature sensor will be exposed only to the ambient air, which will be cooler: 60 degrees or 70 or whatever. In that case, shouldn’t the displayed temperature actually drop?

It is beyond me that cars today have all kinds of sensors but there is none for loss of coolant. If we can have a warning light for low oil pressure, we can very well have one for coolant as well.

Originally Posted by sagarpadaki

Now that you have corrected the cause of leak, do a radiator flush with liquimoly or whatever you like. The tap water you have used will definitely corrode the engine internals.

Tap water was put in Hexa in Rishikesh. Outstation emergency situation, so yes, obviously. With the City, since we were home when the problem was discovered, only RO water was used to fill the radiator and reservoir.

Radiators were flushed and coolant was replaced after the repairs were carried out. It is standard practice to flush the radiator whenever coolant is changed. Even the SAs will proactively suggest the same. Of course, their motivation is selling you the extra service!

[sandeepmohan]

Originally Posted by Shreyans_Jain

And do lift up the hood and take a good look at the engine bay every now and then. I have been fortunate. You never know when your luck runs out.

You can't say this enough.

The thing is, we have gotten used to the dependability of a modern vehicle, hence, less of a need to think about such things. We talk about this here as automobile enthusiasts. We care for our cars. The regular joe out there ain't bothered. The vehicle goes in for a yearly inspection or service and the expectation is that anything that does need attention is seen to at this point. We may play the "cheap" card when the car goes for service. Something that needs replacement may be put away (for next time) due to their cost. I never delay anything around the engine cooling system that needs replacement. Its annoying cause they play on the back of your mind, if you ignore it.

I've come to understand that even if you do end up with a steaming engine, as long as you stop immediately, you're all good. However; not knowing the state of your engine temperature is really bad. With regard to weak or worn rubber hoses, an inspection is the only way.

I've seen another iteration of poor design. This was on the first generation Wagon R sold in India. When there is no water in the cooling system, the temperature read out drops to C. If you don't notice this nor you know how the system works, you'll end up with steam in no time. Just like you experienced, the car will continue to run till a point comes where the engine can't take it anymore.

I owned a Ford Ikon 1.6l. This car had a pretty good warning system. Two tell tale signs that all isn't well. In true Ford service fashion, the technicians forgot to connect the radiator fan back after refitting the stock air box. I picked up the car drove home and all was okay. Stepped out later in the day and the aircon started cutting out. Turned off the aircon and dropped the windows down. Noticed the temperature gauge was a little over its normal position. As we drove, it started creeping up. A little steam was noticed from the edge of the windscreen when the gauge had reached the 80% mark. That is the location of the expansion tank too. I stopped immediately and let the engine cool down. Restarted and drove to Ford. Cut the engine out at traffic lights so it does not build up heat while idling. This allowed us to reach without any more steaming. That temperature gauge was a engine saver for sure.

[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 was able to check and adjust driving using diagnostic mode temperature display. Since this happened on highway in both instances, had to drive ~50 kilometres distance in both instances with windows rolled down, heater running to dissipate engine heat(in summer season of June ), driving at a consistent speed of 60kmph in 6th gear, ensuring car operators just below the turbo spooling RPM. 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.

[R2D2]

Originally Posted by Shreyans_Jain

This is news to me. In our older cars, WagonR F10D and Scorpio 2.6DI, the temperature gauge used to always throw a fit at the slightest loss of coolant or overheating. And there were quite a few such instances over the 13 and 15 year ownerships of the cars respectively. We lost a few radiators due to dog hits during the Delhi-Mumbai night runs we used to do back then. The temperature gauges always did their job.

Well, whether the gauge or sensor works or not depends on where it is placed in the engine block and how much coolant has leaked out. A leak doesn't necessarily mean that the sensor remains immersed in coolant or not. It all depends on the manufacturer's design among other things.

Going by your reasoning, normal temperature is the temperature of the coolant on a fully warmed up engine, which is about 90 degrees celsius. Now if the coolant empties out suddenly due to any reason, the temperature sensor will be exposed only to the ambient air, which will be cooler: 60 degrees or 70 or whatever. In that case, shouldn’t the displayed temperature actually drop?

I am not sure I can answer what all temp sensors will show with any level of surety as I have not done a methodical survey to ascertain how each sensor in each engine will behave if not immersed. But the sensor works only when immersed in fluid, it also heats up due to the heat of the operating engine block itself but the main reading is from the fluid temperature. Similarly a coolant system valve operates the same way, i.e. immersion in fluid of a certain trigger temperature value is required for it to open and allow circulation. In other words no fluid present results in either no or incorrect operation. Which is why I say do not depend on the temp gauge to reliably tell you of some crisis occuring in the coolant system. Visual inspection and of course the smell of burnt coolant (as you experienced) are the best indicators of a coolant leak.

It is beyond me that cars today have all kinds of sensors but there is none for loss of coolant. If we can have a warning light for low oil pressure, we can very well have one for coolant as well.

Absolutely! These systems work under pressure and at a certain temperature given the operating condition of the engine i.e. RPM, road speed, air flow across the heat exchanger, pump speed among other parameters. I am sure teh engineers can work on a sub system that monitors these values and more to warn the driver. Thing is, it costs them money and I am not sure auto companies' bean counters will be particularly enthusiastic about these features.

[Raghu M]

I will share my experience. I used to drive a 96 Maruti 800 (bought second hand in 2008). The car was well built and ran around 65K when I bought it. I was driving to Kurnool along with my friend. We were doing speeds of around 80 kmph. I noticed some green splash on the bottom of the windshield. I mentioned about it to my friend but he said it's nothing. I also assumed it could be from some lorry that was passing by. We drove on. The temperature gauge was sleeping all the while (meter model).

We hit Kurnool entry toll and while I was paying money (in 2009), there was a huge sound from the engine. It was just like a T-Rex roar. It just took my breath away. There were 2 employees on that toll box who just jumped out and began to run away. I was clueless. Immediately I could see huge smoke emanate from the bonnet. It was just confusing. We jumped out of the car and waited for a few mins. The entire toll plaza turned chaotic and people were just peeping to take a look at what happened. Then one guy (mechanical background) came to me and asked me if the coolant is fine. I said, I had no idea, he opened the bonnet and to our utter shock, the entire coolant can was dry and green liquid was splashed all over. He said you are very lucky that nothing happened, or else the engine would have torn apart. We slowly moved the car away, I called my local mechanic in Hyd. He asked me to fill in coolant and water. I did and we waited for 30 mins, the car cranked and we took it to a mechanic. He opened the bonnet and mentioned that the head gasket had given up and would need a replacement. The heat gauge meters wire had snapped (surprising) and he re-attached it.

I was not confident about the mechanics work, so called my guy in Hyd. He gave some instructions to the mechanic (fan direct - meaning as soon as you put the key in the ignition, the fan will start running without the engine being switched on). This was done to ensure the radiator stays cool. We drove back to Hyd slowly and the total repair cost was around 3K.

Always check the below while going on long trips.

1. All lubes (ensure the caps are tight, this is generally taken for granted)
2. Always try to park in the shade (all the cars that are left to bask in the sun everyday needs regular checking)
3. While driving and taking a break, just inspect the bonnet once in a while, check for lube splashes around and also check the place under the bonnet after parking
4. Always good to carry 1 litre of coolant and water (never let the level go below the mid mark)
5. Do not open the radiator cap if the engine is hot
6. While pouring the water (after engine has cooled down), try to start the engine and then pour water. If you see foam in the water, visit the nearest workshop ASAP. It's most likely that the gasket has gone kapoot.

[Piyush Kanthak]

Well let me share my experience too, also I need an explanation.
My SX4 has completed 14 years and had gone for it's regular service, coolant was changed, but this time the coolant was in yellowish colour, I didn't have time to think about it as there was a wedding at my home, my car ran about 2,000 km in just 3 months. All this time the A/C was on with temperatures around 25-34C.
Later I went on for a regular inspection of the engine bay as I was free after all the wedding was done.
I was shocked to see that the coolant was empty, not even a single drop. The car gave no Indications, temperatures we all within range. I checked all hoses thoroughly, but couldn't find any leaks.
Took her to a FNG, he just added distilled water and told that the radiator had coolant in it. Moreover the color of the coolant was now green. How is this possible?

[viXit]

Hi shreyans_jain,

Could you pls share the invoice or the part number for the hexa's damaged hose.

I had a coolant leak and replaced a hose or two last week. You can find the invoice on the storme thread , it's my previous post.

Curious since we have the same drivetrain, i think we might have a common point of failure that would be a good thing to look at as preventive maintenance for other varicor owners

And the city diesel too

I have a 2016 IDTEC and an curious as to what exactly failed in your car.

Much thanks!

[arjithin]

OT: Two of your car developing similar issues in a span of 2 months. Is that a pure coincidence or something else??

Are these cars parked closer? Did you check the nature of the hose damage?