Hello Nairalanders, I come across this piece in a Pakistani forum. Read on....
PART 1
direct connection radiator fan is harmful
i want all Pak Wheelers to inform dem about serious draw backs by direct connection of radiator fan in ur ride.
Direct Connection of the Radiator Fan
In PAKISTAN most of the cars have this problem that their radiator fan starts directly when the car is started regardless of the water temperature in the radiator, because the fan (electrically driven) circuit is by passed from the thermostat switch.
Well our mechanics do this because they think that by keeping the water temperature (indicated at the control panel by temperature gauge) to the minimum possible level will help engine perform well.

Actually the normal operating temperature of the engine, referred with respect to the water temperature in the radiator is 82 ± 3 °C. It is important to note that the water in the radiator boils at 115 to 120 °C .The radiator cap keeps the water under pressure and that is why the water boils above the its normal boiling point. The calibration of the gauge starts from 50°C .So the total range on the dial of the gauge is from 50°C to 120°C. So when needle reaches the middle of the gauge, engine is actually at its NORMAL WORKING TEMPERATURE {average temp of the gauge (as averages fall in the middle) is (115+50)/2=82.5 °C}. So at the normal working temperature the needle should be somewhere in the middle of the gauge. Whereas our so-called skilled mechanics interpret this as over-heating of the engine.THIS IS TOTALLY WRONG!

PART 2
In a moment I will be listing the disadvantages of having your radiator fan direct .But first I would like to tell the readers about the cooling system of the engine in brief .

In water circuit of the engine (water circuit means the path of the water in engine) the effort is made to keep the water away from radiator till the water temperature in the water jacket reaches the 82°C mark. Simply you can say that water is not allowed to go in the radiator and is made to circulate inside the water jacket. This is done by using a device called THERMOSTAT VALVE. This thermostat valve when closed does not allow the water to circulate in the radiator. As soon as the temperature starts to go beyond 78°C the valve opens. This allows the water to be circulated in the radiator. If the heat dissipation of the radiator cannot keep the temperature at about 82°C the THERMOSTAT SWITCH completes the circuit of the electrically driven radiator fan to keep the temperature at 82°C by circulating air.

IT IS IMPORTANT TO NOTE that if temperature goes beyond 82°C it is comparatively acceptable as the most likely disadvantage is the increased potential of the engine to knock at higher gear and low engine rpm .

But if the temperature is less than the normal operating temperature then it will cause not only the deterioration of the engine performance but also shortening your engine life.

So in most of the cars the thermostat valve is removed, making the water circuit complete all the times and also bypassing the thermostat switch to keep fan running with engine regardless of engine temperature .

The problems that can arise as a result are discussed below:

Problems associated with Carburetion
Mixture Preparation 
The petrol air/mixture preparation in the carburetor is a temperature dependent function. To keep the mixture preparation efficiency maximum the water in the radiator and water jacket is fed to the outer walls (around venturi) of the carburetor to keep it warm. 

This increase of the temperature helps to mix up the petrol/air. If the temperature of the water is not at optimum, the petrol air mixture preparation in the carburetor will be effected .This will cause the engine to run on non-homogeneous mixture causing engine to misfire and vibrant engine operation is resulted.

One must have noticed the vibrant engine operation on cold starting in the morning. This is also due to the same reason as engine temperature is very low and mixture preparation is not good.

So by keeping the fan direct you are going make the engine run with vibrations and it will not deliver its full power as the mixture (petrol/air) is not homogeneous (well prepared) .

Mixture Distribution 
If the temperature of the radiator water is kept low then the carburetor temperature also keeps low as the water circulates around the carburetor venturi (the cylindrical passage down the carburetor where air/petrol gets mixed) .The optimum carburetor operation is achieved at higher temperature. So by keeping the fan direct temperature is kept around 55 to 60 °C. This not only effects the mixture preparation but also the mixture movement as well. The mixture is prepared in carburetor and burnt in the cylinder. To get to cylinder the petrol/air passes through carburetor venturi and inlet manifold. If the temperature of venturi and manifold is low then the condensation of the petrol takes place. This will also cause the engine to run on non-homogeneous mixture and the engine running results will be the same as discussed in the above case .

It is important to note that if the mixture fed to the cylinder is not homogeneous then the combustion will not produced the desired amount of power .By meaning the homogeneous mixture it is assumed that the mixture strength expressed by weight ratios is same through out the mixture volume .The combustion is so fast that in non homogeneous mixture the petrol will not burn in the areas where not enough air is not present .This results in loss of fuel and engine produces less power .So by keeping your fan direct you will actually be doing the same thing as discussed above as water temperature will be low.

Problems associated with Engine 

Four Stroke Cycle 
As the engine temperature is not measured directly but is measured with respect to water temperature in the radiator so when the temperature of the radiator water reaches somewhere around 115 to 120°C, the temp. of the engine is enough to cause serious engine damage and it can even result in ceasing the engine .

The point here which I would like to emphasize is that engine temperature is never measured directly but the water temperature is measured. So if water temperature is low so is the engine temperature.The discussion to follow will be carried taking the radiator water temperature as reference.

When engine is started the temperature at the piston top or piston temperature is very low, same as atmospheric temperature. During engine operation it reaches hundred of degrees centigrade. No metal or alloy is developed yet which has zero expansion rate. So to accommodate the expansion the piston is made oval shaped. At cold starting the piston does not completely seal the cylinder, but as temperature rises the piston expands and seals the gap. At water temperatures above 115 to 120 °C the expansion is so great that the piston gets stuck resulting in serious engine damage. Below temperatures of say 75°C the piston is loosely fit in the cylinder.

We will discuss engine condition keeping in mind that water temperature as it is less than 75°C as fan is made to operate directly preventing the engine to operate at its normal working temperature. 

Intake stroke 
When the normal operating temperature of the engine is not achieved then the piston is not complete fit in the cylinder. During intake stroke piston descends from TDC(top dead center) and reaches BDC (bottom dead center). So if the piston is not completely fit than the petrol/air will not be sucked in properly. This will result in low engine volumetric efficiency 

Compression Stroke 
During compression stroke piston reaches from BDCto TDC. If the temperature of the piston is below normal then it will not fit the cylinder. So the petrol air sucked in prior ot compression, when compressed during compression stroke will bypass the piston and piston rings into the crankcase (It will be discussed in detail later on). So full compression is not achieved and this results in lower engine output and higher fuel consumption .

Power Stroke 
During power stoke the rapidly expanding gases pushes the piston down giving power. If the piston does not fit completely then the expanding gases will by pass the piston rings thus resulting in incomplete power transfer making the engine H.P to decrease and fuel consumption to increase .

Exhaust Stroke 
During exhaust stroke if piston is not complete fit then the exhaust will not be good. The exhaust air will by pass the piston, rings and will reach the crankcase causing oil fouling (it will also be discussed in detail later on) .

Engine Oil Fouling 
(a) If the engine is made to run on low temp than optimum then the compression stroke is not fully efficient. The petrol/air mixture instead of being compressed, by passes the piston and piston rings. On its way to crankcase it passes the cylinder wall. The cylinder walls are soaked with engine oil to lubricate piton and rings. So when petrol by passes the piston rings it mixes with the oil on the cylinder walls. Petrol being excellent organic solvent dissolves and dilutes the engine oil, promoting engine wear .

(b) During power and exhaust stroke the burnt gases which are normally non metallic oxides (acidic in nature) bypass the piston rings and enter the crankcase. Here these gases mix with the water vapors. This forms acidic compounds that get mixed with engine oil resulting in altering the oil PH. It makes the engine oil acidic and corrosion always takes speeds up in the acidic medium.

For this reason the engine oils are made buffers (which can retain there PH although some amount of acid is added to them). But they can retain there PH only if a small amount of acid is added. So if engine is run consistently on low temperature then it will promote engine wear as engine oil will get acidic .

(c) The unburnt particles from the combustion chamber also by pass the piston as they are very small in size. When they enter the crankcase they get mixed with the oil. The engine oil are made detergents. That is they can accumulate small amount of these particles and hold them in suspension or you can say dissolve them. But this tendency is limited to a small amount. If prolonged use of engine at low temperature is carried out then it will cause pre mature engine wear.

As these particles do not completely dissolve in oil, they narrow down the small channels in engine lubrication circuit. This effects the engine lubrication as proper amount of oil is not fed to the moving parts resulting in engine wear.



Summarizing

PART 3
The following are the problems summarized keeping in mind that if engine is not running on its normal working temperature.

(1) It will decrease the air/petrol mixing efficiency .
(2) It will effect the distribution of petrol/air mixture to each cylinder.
(3) This will decrease the volumetric efficiency of the engine resulting in increased fuel consumption .
(4) The engine oil will get fouled prematurely resulting in more oil changes .
(5) The fouled engine oil will result in the premature engine wear shortening the engine life.
(6) Vibrant and rough idle (low speed running).
(7) Engine will never give its full power and torque .
( It will increase the fuel consumption without increasing the output of the engine .

Rear wheel Drive Cars 

In rare wheel drive cars the radiator fan is not electrically driven but it is belt driven. It starts running as soon as the engine is started. To keep the engine temperature at optimum level the water is not allowed to circulate (when cold) in the radiator as the THERMOSTAT VALVE remains closed. As soon as the temperature starts to rise the valve is opened and the belt driven fan keeps the air circulating making the water temperature stick to an optimum level.

So in rear wheel drive cars the Thermostat valve should NEVER BE REMOVED. As it will result in the same problems as discussed above (by removing thermostat valve and making fan direct in front wheel cars) .

The End
Source http://www.pakwheels.com/forums/engine-transmission-powertrain/76048-direct-connection-radiator-fan-harmful-3

very concise explanation..i hope all those semi ignoirant mechanics and rewire that love doing this would read this thread

Nice1

I have a mazda 6 and the car started doing over heating so i was advised to remove the thermostat and the fan got connected directly, it work fine for some time but i later noticed that the car is noisy than before and the water in the reservoir always go down after 2 days..i have been thinking of connecting back the fan in the normal way it should be but after reading this thread i have more confident of doing that..All i want to know is it necessary for me to put back the thermostat as well or i should just disconnect the fan from working directly..And what can i do about the water in the reservoir that always go down, i top it almost everyday..i dont like that..

Siena:

Put your thermostat back, and get your electric fan back the way it should be - i.e switching on when the coolant temperature rises. This has been stressed over and over and over again on Nairaland, but all advice falls on deaf ears.

Your coolant loss is not related to your thermostat missing, or your direct-drive fan. You either have an external leak, or an internal one (blown head gasket, or cracked block / head.

#JusticeforAluu4

Have the same issue. Who can do this for me? A road side mechanic?

Siena:

Put your thermostat back, and get your electric fan back the way it should be - i.e switching on when the coolant temperature rises. This has been stressed over and over and over again on Nairaland, but all advice falls on deaf ears.

Your coolant loss is not related to your thermostat missing, or your direct-drive fan. You either have an external leak, or an internal one (blown head gasket, or cracked block / head.

#JusticeforAluu4

But The Mechanic insists that the overboiling of the water in the radiator is because of the thermostat in the 99 camry.

Dear Nairalanders,
Increase the life span of your vehicle by connecting your vehicle fan to thermo swith. i.e disconnect your fan from direct connection. So harmful!

captalex:


But The Mechanic insists that the overboiling of the water in the radiator is because of the thermostat in the 99 camry.

Overboiling or overheating in ur cooling system is a symptom of a problem.Kazeems suppress the symptons by removing thermostat ,using double radiator and running your fine direct.All this method will create more problem for ur engine in the lomg run.so why dont u find a competent person to detect the source of the problem instead of taking advice from illiterates that will put holes in your pocket.
Detecting leak in your cooling system might require some tools that kazeems cannot lay his hands on .
so the easier way is to suppress the issue and tell u to bring the any amount u have .But a professional will detect the issue and fix the problem for u and charge u professional fees.
So in other words ,stop patronizing kazeem!!!

captalex:


But The Mechanic insists that the overboiling of the water in the radiator is because of the thermostat in the 99 camry.

Truely, the thermostat can do that when it is stuck closed. The ideal solution is replacement and not removal.
Also note that bad radiator pressure cap can cause it.
Always use radiator coolant solution rather than water. it has higher boiling point.
BR.

Last week Friday l had 2 coils blown out, went to the mechanic close by and he changed the bad coils, all was fine again until yesterday again with same thing happening.

Prior to this the car was idling with the AC on for about 20 minutes waiting for someone, called the mechanic again he tried everything possible with no head way.

1.He cleaned all 8 plugs.
2.He changed the bad coils but as soon as l start the car its blown again.
3.He checked the air filter which was badly clogged but he dusted it before replacing it.

His advice was to disconnect the thermostat l just laughed inwardly,change the radiator from the single cell to double cell.

My plan is to scan the car again next week, change all 8 plugs and 8 coils, the temperature gauge has always been in the same position since I bought the car, I have a feeling I need to flush the radiator.

Any ideas from the house?

Osama10:
Last week Friday l had 2 coils blown out, went to the mechanic close by and he changed the bad coils, all was fine again until yesterday again with same thing happening.
Prior to this the car was idling with the AC on for about 20 minutes waiting for someone, called the mechanic again he tried everything possible with no head way.
1.He cleaned all 8 plugs.
2.He changed the bad coils but as soon as l start the car its blown again.
3.He checked the air filter which was badly clogged but he dusted it before replacing it.
His advice was to disconnect the thermostat l just laughed inwardly,change the radiator from the single cell to double cell.
My plan is to scan the car again next week, change all 8 plugs and 8 coils, the temperature gauge has always been in the same position since I bought the car, I have a feeling I need to flush the radiator.
Any ideas from the house?

Dear Osama10,
Kindly post your issues on a new tread, by doing so, it would attract expert opinions. Thank you

Thermostat and relay, are they the same?

abidemidare:
Thermostat and relay, are they the same?

not at all,a thermostat is purely a mechanic device while relay is electromechanic .

Thanks for this post.

I have a problem with my Honda Accord V6 2010 model. I recently replaced the thermostat as the old one was stuck in the open position (found during routine scanning of the car). Prior to changing the thermostat and even now after changing it, I've noticed that the coolant level drops low some mornings, meaning that I have to top it up with more coolant. I noticed this because I have a habit of checking my coolant level every morning, being scared of an unexpected overheating (Its a long time habit from previous cars)

I saw something concerning an internal leak (I have not noticed any obvious external leakage). Is this the possible reason for the low coolant level sometimes? How can an internal leak of this vehicle be discovered and what is the possible remedy?

The car is fine and does not overheat. The fan comes on intermittently.

I would appreciate some kind suggestions.

[quote author=drdanny post=31491063]Thanks for this post.

I have a problem with my Honda Accord V6 2010 model. I recently replaced the thermostat as the old one was stuck in the open position (found during routine scanning of the car). Prior to changing the thermostat and even now after changing it, I've noticed that the coolant level drops low some mornings, meaning that I have to top it up with more coolant. I noticed this because I have a habit of checking my coolant level every morning, being scared of an unexpected overheating (Its a long time habit from previous cars)

I saw something concerning an internal leak (I have not noticed any obvious external leakage). Is this the possible reason for the low coolant level sometimes? How can an internal leak of this vehicle be discovered and what is the possible remedy?

The car is fine and does not overheat. The fan comes on intermittently.

I would appreciate some kind suggestions.[/quotppe]

Since u are always opening ur radiator cap , u might have ruin it by damaging the seals.A bad cap will not be able to hold pressure and coolant will be leaking past the radiator into the reserviour.
Change the cap first before u start checking for leaks in the system.

[quote author=honmusa post=31511353][/quote]

Thanks for your comment.

I forgot to add that the reservoir is also dry. even if i put coolant in the reservoir, it dries up too.

I am going to change the cap but I might also think this might be more serious.

drdanny:


Thanks for your comment.

I forgot to add that the reservoir is also dry. even if i put coolant in the reservoir, it dries up too.

I am going to change the cap but I might also think this might be more serious.

What kinda liquid are u using as coolant? Ordinary water maybe or coolant liquid/ditilled water?

drdanny:


Thanks for your comment.

I forgot to add that the reservoir is also dry. even if i put coolant in the reservoir, it dries up too.

I am going to change the cap but I might also think this might be more serious.

japanese cars reservior are always vented to allow outflow of air in the cooling system.so coolant escaping through ur defective radiator cap can still flow out of ur reservior vent cos it is under pressure.so still go ahead and change ur cap.

uwemjack:


What kinda liquid are u using as coolant? Ordinary water maybe or coolant liquid/ditilled water?

I use proper coolant not water.I've bought almost 6 liters in 3months

my vehicle also had the same overheating issue as a result of faulty thermostat, and my mechanic replaced it with something they called "relay", which makes the fan turn on when the vehicle is started. Is this the same thing you guys are warning against pls.

Thanks

valarinz:
my vehicle also had the same overheating issue as a result of faulty thermostat, and my mechanic replaced it with something they called "relay", which makes the fan turn on when the vehicle is started. Is this the same thing you guys are warning against pls.

Thanks

.
exactly , why cant ur mechanic just replace faulty thermostat instead of runing fan directly ,he is indirectly creating holes in ur pocket by doing that and u run the risk of replacing ur engine soon.
.

As these particles do not completely dissolve in oil, they narrow down the small channels in engine lubrication circuit. This effects the engine lubrication as proper amount of oil is not fed to the moving parts resulting in engine wear.
http://www.gari.pk/used-cars/suzuki/wagon-r/islamabad-c/

I’m impressed, I must say. Really rarely do I encounter a blog that’s both educative and let me tell you, you have hit the nail on the head. The issue is something that not enough people are speaking intelligently about. I am very happy that I stumbled across this in my search for something relating to Car Rental Singapore.

Wow! So educatiive . I am impressed with this. Kudos guys

Awesome thread

Hi, Please tell me about Suzuki's swift price in Pakistan. It has good features, Bluetooth, power steering, etc. Some people are speaking for it and some are against it. I just want to know from people who have bought it or planning to do so. I am sharing a blog that I found very useful:
https://rentole.pk/blog/suzuki-swift-price-in-pakistan

Please how to correct this if already don in car. I would be glad if I get solution. Thanks 08143321347