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Old 31st March 2016, 22:01   #91
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

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Originally Posted by Ravindra M View Post
No need to keep the hood up to keep the engine cool as such. It reminds me of the bygone era - Ambassadors fitted with Matador engines - which needed it frequently.

As long as the car is being driven, the airflow ensures that the excess heat is dissipated. The engine room temperature settles around 90 deg.C. All parts in the engine room are designed for it.

But when the car is resting after a long drive, the engine room temperature continues to raise in absence of air flow. It may reach as high as 110 deg.C. Although the plastic parts and electrical parts are designed to withstand this much of temperature, I always felt to keep the hood open so that the excess heat is not trapped and plastic parts don't degenerate. This I do it for my modern classic car Mercedes W124, just for the peace of mind. I don't do it for other cars which are more modern.

If you travel long distances very frequently with heavy load and in summer and you have an older car, it is a good idea to do it. But also be aware of other factors like safety and convenience which are more important.

This defies the laws of heat transfer. If the engine temp has been maintained at 90deg till the end of the drive, it does not matter how long the engine has been running. If the engine temperature has to rise to 110 deg or whatever after shutting down, it would rise to the same irrespective of the duration of the run.
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Old 1st April 2016, 19:33   #92
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

Hood-up procedure is most apt for the ghat climb sections. Engine temperature goes up because (my guess) of low gear + high RPM + low airflow during the continuous steep climb. I see lot of cars (petrol/diesel) with their hood up on the Peermade – Vandiperiyar – Thekkady/Kumily (NH220) section. Don’t think it is needed for flat out NH7 kind of runs.
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Old 2nd April 2016, 14:25   #93
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

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Originally Posted by phynix123 View Post
Yes sir, As already mentioned in the previous post, I am pretty sure that the fan continues to run even after turning off the engine (even removing of the keys). However, it runs only for a few seconds until heat dissipates.
The car i am mentioning here is chevrolet spark.
I wonder why many manufacturers still dont have this feature. I have owned SX4, Figo, Liva and my extended family has Verna, Santro and i did not notice this feature in any. However, during my initial years when i had a M800, the fan would usually start when i reach the destination and i had to keep the engine running for about 30 seconds before this fan would stop.

I personally feel that this feature is a brilliant one considering the hot condition we drive in and a cool down just before switching the engine off would always help.
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Old 2nd April 2016, 15:36   #94
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

In my Alto I have heard the fan running only when the ignition key is in the "on" position, even if the engine is not running. If you turn the key completely off, the fan does not run.
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Old 2nd April 2016, 19:47   #95
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

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Originally Posted by Gansan View Post
In my Alto I have heard the fan running only when the ignition key is in the "on" position, even if the engine is not running. If you turn the key completely off, the fan does not run.
Sure, on some cars this happens, on others the fan might still run

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Old 2nd April 2016, 22:17   #96
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

Just FYI, the Classic that we have has a fan that runs after she has been shut off, in the most extreme of cases. This is happened only once in our ownership period. We were back from a road trip and she had run over 600kms that day over varied conditions. After returning, I made sure that the engine stays on for a couple of minutes. Even so, after I shut off the engine, the fan kept running for about three minutes. I didn't interrupt. After the fan went off, I unlocked her, and checked the secret menu for temperature. It showed a perfectly normal 93 degree Celsius. I went to sleep peacefully.

Generally, after these long drives, I always makes sure to check the secret menu for temperature. Until now, it has never crossed 105. Once she does, I think the logical step would be to open up the hood?

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Old 14th June 2016, 00:50   #97
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Talking Re: Do we need to keep the hood up to cool the engine after a long drive?

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Originally Posted by Lobogris View Post
Why did you keep your engine idling for 4 hours during breaks? Was it for ac use for some passengers left in the vehicle? It is a good idea to get out and stretch for at least 10 minutes after a long drive and the engine can be switched off for a break during that time as well. If nothing else, you reduce pollution and save fuel.
Yes, I take more breaks than my spouse or anyone on this forum would appreciate. Every 150km or 2 hours whichever is earliest. We were traveling with our faithful family member in the backseat. Who enjoys drives while her crate is strapped using a seatbelt.



She does not venture out everytime we take breaks. Engine idling during the break is a necessity, especially when you cannot find trees to park under OR a large parking area away from road to enjoy nature. Gone are the days. NHAI has done away with planting trees; painting them red & white and using them to install reflective markers!
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Old 14th June 2016, 10:25   #98
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Thinking again.

Cooler engine is prone to wear. Why? All engine components are sized to work best at optimal engine temperature. So the rings, pistons, valve stems, valve seats etc. Would have expansion margins to suit working at optimum temperature.

So if we are on continued journey cycle why cool the engine more than needed when it has to heat up again to optimum temperature?

Have I stirred a hornets nest? Guru's opine please.
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Old 14th June 2016, 10:50   #99
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

^^
Actually there is no need to open the hood except if one wants to check for any inadvertent damage etc.

To cite and example,I haven't ever seen a bus driver leave the hood open after a long drive.

If the engine and coolant system are in good health, the temperature gauge would never cross 50% of range in normal driving conditions.
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Old 14th June 2016, 11:05   #100
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

The cooling system is designed to liberate as much heat as is generated while allowing the engine to maintain a specific temperature. Now, a high speed run means higher heat generation due to continuous high RPMs. At the same time, it also means better cooling due to high speed air flow for efficient heat exchange. This compensates for the higher temperature. For the city runs, we don't have good air flow but then, in such cases, we have space for high speed runs too.

Overall, I feel, prolonged use in heavy city traffic and AC, is more damaging than a high speed highway run. I haven't checked the engine temperature but the bonnet of my car feels hotter in the former case, signalling poor heat dissipation.
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Old 14th June 2016, 11:19   #101
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

In my Clelerio VXi, there is no temperature gauge. So is the case of new Alto,I think. There is only a warning signal,which never glows,even after I have an 800 Km road trip. Current engines are efficiently designed to get better mileage and longevity.
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Old 14th June 2016, 11:27   #102
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Over time as components reliability improves the need for constant monitoring goes down.

Example in days of Ambassador not only temperature but also oil pressure guage was a must.

With better technology of components and oil quality these disappeared from dash boards.
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Old 11th October 2016, 13:15   #103
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

The radiator does duty for reducing temperature of radiator water/coolant mix and also the a/c condenser coil, so with this understanding in mind, i would like to know whether a engine will experience better heat dissipation when run the car in summers with A/c as radiator fan spins all the time trying to keep both cooling mechanisms in check.

I own a Grande Punto MJD and most of times during window rolled down driving scenario (A/c not running) in summers, i still witness radiator fan not running at all, Then i turn on my AC and let the fan run in full speed for 3-4 mins before turning of the engine, i do this after i arrive at my destination

So does this imply turning the A/c not only cools the cabin but also proactively cools the radiator water before even the threshold limit has reached for the fan to start when A/c is not functioning ?

In the interest of better engine heat dissipation in summers, should i use the A/c all the time ?

Last edited by sriramr9 : 11th October 2016 at 13:18.
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Old 16th October 2016, 19:37   #104
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Default Re: Do we need to keep the hood up to cool the engine after a long drive?

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Originally Posted by sriramr9 View Post
The radiator does duty for reducing temperature of radiator water/coolant mix and also the a/c condenser coil, so with this understanding in mind, i would like to know whether a engine will experience better heat dissipation when run the car in summers with A/c as radiator fan spins all the time trying to keep both cooling mechanisms in check.

I own a Grande Punto MJD and most of times during window rolled down driving scenario (A/c not running) in summers, i still witness radiator fan not running at all, Then i turn on my AC and let the fan run in full speed for 3-4 mins before turning of the engine, i do this after i arrive at my destination

So does this imply turning the A/c not only cools the cabin but also proactively cools the radiator water before even the threshold limit has reached for the fan to start when A/c is not functioning ?

In the interest of better engine heat dissipation in summers, should i use the A/c all the time ?
Hi Sriram,

As you mentioned A/C fan is used to cool the air coming in to the cabin via a/c cooler matrix. Also when A/C is switched on (thereby switching ON the A/C compressor) an amount of load is exerted to the engine. So an extra engine heating is expected. Still, if the engine temperature goes above the fan trigger limit, it will activate the normal cooling fan.

So for new Gen cars, you don't have to do anything like you are doing. IF you are running a/c at engine idle, you are putting more load to the engine and the cooling system does not get any air to cool either. Remember even though an electric fan blows air to the cooler, it indirectly puts load on engine (via alternator charging the battery).

So as a good practice, drive the car under low load (light pedal and no A/C) for the last leg of your journey, so that the cooling system gets a chance to cool the engine normally and stop at your destination.. Again it is not a mandatory practice.

Hope it helps.


Kannan.
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Old 16th October 2016, 20:23   #105
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Putting on the heater will cool an overheating car, though. Tried and tested.
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