Laymans explanation of car cooling system...
Discussion
My car has just gone in for repair - 1.4l Corsa.
It started running a bit on the warm side, then started to get very hot in slow traffic and the temp was fluctuating everywhere.
The cambelt was replaced before I got it, but they didn't replace the water pump.
The garage now has it and it is being repaired under warranty, so all good there.
So out of curiosity - I need to understand how this works...
Surely if the water pump had gone, the engine would just overheat straight off, as there is no internal cooling system cooling the block down. How is it that when driving, it remains almost cool enough to be normal?
I understand that wind in motion would cool it down, but I did not think it would be enough to cool an entire block down...
Help to educate a mechanical retard please
It started running a bit on the warm side, then started to get very hot in slow traffic and the temp was fluctuating everywhere.
The cambelt was replaced before I got it, but they didn't replace the water pump.
The garage now has it and it is being repaired under warranty, so all good there.
So out of curiosity - I need to understand how this works...
Surely if the water pump had gone, the engine would just overheat straight off, as there is no internal cooling system cooling the block down. How is it that when driving, it remains almost cool enough to be normal?
I understand that wind in motion would cool it down, but I did not think it would be enough to cool an entire block down...
Help to educate a mechanical retard please
Some American vehicles have engines which are specifically designed to remain useable despite complete loss of coolant. This is achieved by reducing engine power and shutting down cylinders by rotation so that the engine remains cool enough.
My own experience has been limited to driving a small car whose cooling system had failed. I drove home gently and the car suffered no ill-effects.
Another trick I have used where there's a coolant leak is to leave off the radiator cap - this prevents the system from pressurising so the rate of leakage is massively reduced. You do need to drive gently and top up from time to time.
Having said this, some engines are VERY susceptible to rapid damage in the event of cooling system failure. IIRC these include many BMW engines.
My own experience has been limited to driving a small car whose cooling system had failed. I drove home gently and the car suffered no ill-effects.
Another trick I have used where there's a coolant leak is to leave off the radiator cap - this prevents the system from pressurising so the rate of leakage is massively reduced. You do need to drive gently and top up from time to time.
Having said this, some engines are VERY susceptible to rapid damage in the event of cooling system failure. IIRC these include many BMW engines.
The cooling effect from the wind when driving would be significant.
Another thing worth checking is that the exhaust is not clogged, ex had a 1.2 Corsa and went on holiday with tonnes of stuff. (literally)
I got the call hours later and they were only 40 miles away, 'car wouldn't go fast'.
In a bad mood, I ended up swapping cars with her, to find it wasn't the weight, (it was in my car), but the Corsa, it had no power, and was running hot.
After a nerve wracking drive back at less than 25mph, I found that the wadding in the silencer was coming loose, blocking the exhaust and chocking the engine.
Another thing worth checking is that the exhaust is not clogged, ex had a 1.2 Corsa and went on holiday with tonnes of stuff. (literally)
I got the call hours later and they were only 40 miles away, 'car wouldn't go fast'.
In a bad mood, I ended up swapping cars with her, to find it wasn't the weight, (it was in my car), but the Corsa, it had no power, and was running hot.
After a nerve wracking drive back at less than 25mph, I found that the wadding in the silencer was coming loose, blocking the exhaust and chocking the engine.
I believe that (generally speaking) all-alloy engines are more susceptible to rapid overheating damage than engines with cast iron blocks. The alloy expands more per degree of heat, so you don't have to overheat it too much before the head gasket mating surfaces part company. My car has a £4,000 bill in its service history from a water pump failure which led to the heads cracking...
Beirut Taxi said:
5 USA said:
Having said this, some engines are VERY susceptible to rapid damage in the event of cooling system failure. IIRC these include many BMW engines.
I have heard this is the case with the BMW M42 found in the E36 and E30 'is' models.the majority of bmw engines suffer this issue, the cooling system on these cars has to be well serviced
Quaint said:
I believe that (generally speaking) all-alloy engines are more susceptible to rapid overheating damage than engines with cast iron blocks. The alloy expands more per degree of heat, so you don't have to overheat it too much before the head gasket mating surfaces part company. My car has a £4,000 bill in its service history from a water pump failure which led to the heads cracking...
Yep my old Monaro with LS2 went the same way (all alloy IIRC), water pump failure caused warped heads.-Z- said:
Quaint said:
I believe that (generally speaking) all-alloy engines are more susceptible to rapid overheating damage than engines with cast iron blocks. The alloy expands more per degree of heat, so you don't have to overheat it too much before the head gasket mating surfaces part company. My car has a £4,000 bill in its service history from a water pump failure which led to the heads cracking...
Yep my old Monaro with LS2 went the same way (all alloy IIRC), water pump failure caused warped heads.DrTre said:
munroman said:
The cooling effect from the wind when driving would be significant.
Really? I'd not have thought so, what with the block being behind the rad etc? I'm intrigued...I want to experiment...(Which is why fans are temperature controlled, it is easy to overcool an engine, especially modern turbodiesels, which can cool down just by going downhill) As we live in a relatively cool part of the world, usually cooling systems are over specced for our conditons.
As the air is a fluid, it will go from a high to a low pressure area, i.e, from the radiator it will likely flow under the car, taking the waste heat with it.
If the radiator is not getting a supply of coolant due to a failed waterpump, it will be cool, therefore the incoming air will be cooler when it hits the engine block, hence the cooling effect is even greater.
Manufacturers spend a fortune getting cooling and intake systems optimised for airflow and drag reduction, then some of them mess it up by using inferior parts as 'cost cutting'.
Or, as a simple reminder, stick your hand out of the window at speed and see how long before it starts to feel a bit cold!
TheCarpetCleaner said:
-Z- said:
Quaint said:
I believe that (generally speaking) all-alloy engines are more susceptible to rapid overheating damage than engines with cast iron blocks. The alloy expands more per degree of heat, so you don't have to overheat it too much before the head gasket mating surfaces part company. My car has a £4,000 bill in its service history from a water pump failure which led to the heads cracking...
Yep my old Monaro with LS2 went the same way (all alloy IIRC), water pump failure caused warped heads.Took 2.5 months for Vauxhall to find a water pump so they could fix it, but thats Vauxhall for you.
early engines like the old morris side valves had no water pump and they relied on convection currents to cool the block.
Depends on the 1.4 motor but a lot use the water pump as a tensioner and if I ever do one I replace it as the parts only cheap and your there any way.
It has been known for them to seize in like a b
d though.
Depends on the 1.4 motor but a lot use the water pump as a tensioner and if I ever do one I replace it as the parts only cheap and your there any way.
It has been known for them to seize in like a b
d though.The water in the block is heated by the engine and circulated by the water pump.
The cooling system is kept under pressure by the radiator cap. The pressure raises the boiling point so your coolant doesn't boil like a kettle.
When it gets hot enough, it melts the wax in the thermostat which then opens and adds the radiator into the coolant "loop" - the water then flows through the radiator where the throughflow of air cools it and the water pump keeps the water loop circulating.
There is an additional "loop" which allows the hot water to pass into a heater matrix and a fan blows air through it to create hot air. this also cools the coolant although negligibly.
The causes of overheating are:
(1) a defective water pump - this can result from wear or breakage of the vanes of the pump
(2) constriction of the water passages through rust or sedimentation
(3) faulty thermostat not opening
However, in most cases, the overheating arises through a loss of pressure which allows the coolant to boil. This can be the failure of the pump itself which often has a seal which leaks (allowing air in and water out), spattering coolant all over the engine bay. it can be holed or split hoses, a faulty radiator cap or a holed/leaking radiator. Often the best thing to do is to pressure test the system first before blaming anything else.
The cooling system is kept under pressure by the radiator cap. The pressure raises the boiling point so your coolant doesn't boil like a kettle.
When it gets hot enough, it melts the wax in the thermostat which then opens and adds the radiator into the coolant "loop" - the water then flows through the radiator where the throughflow of air cools it and the water pump keeps the water loop circulating.
There is an additional "loop" which allows the hot water to pass into a heater matrix and a fan blows air through it to create hot air. this also cools the coolant although negligibly.
The causes of overheating are:
(1) a defective water pump - this can result from wear or breakage of the vanes of the pump
(2) constriction of the water passages through rust or sedimentation
(3) faulty thermostat not opening
However, in most cases, the overheating arises through a loss of pressure which allows the coolant to boil. This can be the failure of the pump itself which often has a seal which leaks (allowing air in and water out), spattering coolant all over the engine bay. it can be holed or split hoses, a faulty radiator cap or a holed/leaking radiator. Often the best thing to do is to pressure test the system first before blaming anything else.
LuS1fer said:
The water in the block is heated by the engine and circulated by the water pump.
The cooling system is kept under pressure by the radiator cap. The pressure raises the boiling point so your coolant doesn't boil like a kettle.
When it gets hot enough, it melts the wax in the thermostat which then opens and adds the radiator into the coolant "loop" - the water then flows through the radiator where the throughflow of air cools it and the water pump keeps the water loop circulating.
There is an additional "loop" which allows the hot water to pass into a heater matrix and a fan blows air through it to create hot air. this also cools the coolant although negligibly.
The causes of overheating are:
(1) a defective water pump - this can result from wear or breakage of the vanes of the pump
(2) constriction of the water passages through rust or sedimentation
(3) faulty thermostat not opening
However, in most cases, the overheating arises through a loss of pressure which allows the coolant to boil. This can be the failure of the pump itself which often has a seal which leaks (allowing air in and water out), spattering coolant all over the engine bay. it can be holed or split hoses, a faulty radiator cap or a holed/leaking radiator. Often the best thing to do is to pressure test the system first before blaming anything else.
As its overheating in traffic, its possible the fan isn't working. motor, wiring or sensor. Put the heater on full blast and see if it cools down.The cooling system is kept under pressure by the radiator cap. The pressure raises the boiling point so your coolant doesn't boil like a kettle.
When it gets hot enough, it melts the wax in the thermostat which then opens and adds the radiator into the coolant "loop" - the water then flows through the radiator where the throughflow of air cools it and the water pump keeps the water loop circulating.
There is an additional "loop" which allows the hot water to pass into a heater matrix and a fan blows air through it to create hot air. this also cools the coolant although negligibly.
The causes of overheating are:
(1) a defective water pump - this can result from wear or breakage of the vanes of the pump
(2) constriction of the water passages through rust or sedimentation
(3) faulty thermostat not opening
However, in most cases, the overheating arises through a loss of pressure which allows the coolant to boil. This can be the failure of the pump itself which often has a seal which leaks (allowing air in and water out), spattering coolant all over the engine bay. it can be holed or split hoses, a faulty radiator cap or a holed/leaking radiator. Often the best thing to do is to pressure test the system first before blaming anything else.
munroman said:
DrTre said:
munroman said:
The cooling effect from the wind when driving would be significant.
Really? I'd not have thought so, what with the block being behind the rad etc? I'm intrigued...I want to experiment...(Which is why fans are temperature controlled, it is easy to overcool an engine, especially modern turbodiesels, which can cool down just by going downhill) As we live in a relatively cool part of the world, usually cooling systems are over specced for our conditons.
As the air is a fluid, it will go from a high to a low pressure area, i.e, from the radiator it will likely flow under the car, taking the waste heat with it.
If the radiator is not getting a supply of coolant due to a failed waterpump, it will be cool, therefore the incoming air will be cooler when it hits the engine block, hence the cooling effect is even greater.
Manufacturers spend a fortune getting cooling and intake systems optimised for airflow and drag reduction, then some of them mess it up by using inferior parts as 'cost cutting'.
Or, as a simple reminder, stick your hand out of the window at speed and see how long before it starts to feel a bit cold!
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