Discussion
Neither my Chim nor my S3 had a fan overide switch so that after killing the engine the fan stayed on. All my other non TVR's have this, why is that? If you were to remove the keys after killing the engine and not let the fans finish, could you damage the engine? I always stand by the car and let them finish but if the engine is off it is only going to cool down anyway... 
Well when you stop the engine the water pump stops churning water around the engine too. So the fans would only create a breeze in the engine bay and slightly help cool some components if it stayed on anyway.
On some new cars (such as our TT) there is an electric water pump which pumps water around after shutdown (not sure if it's just around the turbo or the whole engine). But not on a RV8 TVR.
On some new cars (such as our TT) there is an electric water pump which pumps water around after shutdown (not sure if it's just around the turbo or the whole engine). But not on a RV8 TVR.
Trefor said:That's why when I fitted my two-stage fan kit, I declined to opt for wiring it so the fans stayed on....couldn't quite see the point if the coolant wasn't circulating through the rad.
Well when you stop the engine the water pump stops churning water around the engine too. So the fans would only create a breeze in the engine bay and slightly help cool some components if it stayed on anyway.
Trefor said:
Well when you stop the engine the water pump stops churning water around the engine too. So the fans would only create a breeze in the engine bay and slightly help cool some components if it stayed on anyway.
On some new cars (such as our TT) there is an electric water pump which pumps water around after shutdown (not sure if it's just around the turbo or the whole engine). But not on a RV8 TVR.
err, I don't think it's a water pump, more likely an oil pump to cool the turbo m8. Otherwise oil 'cooks' onto the turbo and causes damage. I'm sure some people remember the old Renault 5 Turbo, that used to run-on for what seemed like hgours after you turned it off.
Tim
TT Tim said:
Well when you stop the engine the water pump stops churning water around the engine too. So the fans would only create a breeze in the engine bay and slightly help cool some components if it stayed on anyway.
On some new cars (such as our TT) there is an electric water pump which pumps water around after shutdown (not sure if it's just around the turbo or the whole engine). But not on a RV8 TVR.
err, I don't think it's a water pump, more likely an oil pump to cool the turbo m8. Otherwise oil 'cooks' onto the turbo and causes damage. I'm sure some people remember the old Renault 5 Turbo, that used to run-on for what seemed like hgours after you turned it off.
Tim
'spose it could be, and what you say makes sense - but I think it's water - I'll ask some people who know.
I remember from somewhere that water can continue to circulate through the engine/rad for a while after switching off simply due to inertia (though I find it hard to belive this would happen for more than a few seconds). That said, the cooling system can 'gurgle' for some while after being switched off, and the cooling effect of fans on rad may induce some sort of flow due to the coolant cooling and moving due to convection (like air above a radiator).
On the one hand: Can it hurt for the fans to stay on until the otter switch switches off?
On the other: Is anything going to get any hotter with the engine off? (I guess it may due to heat soak, but I don't know).
On the one hand: Can it hurt for the fans to stay on until the otter switch switches off?
On the other: Is anything going to get any hotter with the engine off? (I guess it may due to heat soak, but I don't know).
shnozz said:
but if the engine is off it is only going to cool down anyway...
I'd agree but... if I've been driving in cool conditions and stop (say to fill up with fuel) when I start the car up again it has usually got hotter by about 10 degrees. What's that all about? Usually this is from about 70deg to 80deg and it then maintains 80deg
GarryM said:
but if the engine is off it is only going to cool down anyway...
I'd agree but... if I've been driving in cool conditions and stop (say to fill up with fuel) when I start the car up again it has usually got hotter by about 10 degrees. What's that all about? Usually this is from about 70deg to 80deg and it then maintains 80deg
Heat soak I assume..
I like my fans to continue for the one cycle. I do have an AGA that manages to do the hot water and run a couple of rads without a pump, (in the house of course). I can not think of anything under the bonnet that would like to see more heat when you turn off the ignition though.I would put a bet that most people after a serious hot run would turn their ignition back on for the fans to come on.
Hi Phil
Just my 2 penny`th worth, if the fans are on when i come to the end of a journey i will always wait until they turn off, (leave to idle) this will help to reduce the amount of heat soak in the engine, hence the increase in temp when you come to restart after say 10 mins, very hot water which is not recirculating around the engine can in extreme circumstances blow the cylinder head gasket due to the build up in pressure i`ve let both the Chim and Tuscan idle down in these situations
Tony
Just my 2 penny`th worth, if the fans are on when i come to the end of a journey i will always wait until they turn off, (leave to idle) this will help to reduce the amount of heat soak in the engine, hence the increase in temp when you come to restart after say 10 mins, very hot water which is not recirculating around the engine can in extreme circumstances blow the cylinder head gasket due to the build up in pressure i`ve let both the Chim and Tuscan idle down in these situations
Tony
Agree with T88CAN with this one. Parts of the engine block and head are well above 200 deg C at key-off, and at these points you can get localised boiling of the coolant. This leads to a pressure rise in the coolant which puts stress on the head gasket, coolant hoses and seals.
A trick I use (similar to T88CAN) is if the fans come on key-off I leave it to idle, but I also switch on the heater fan to full and heater control to hot while I wait for the fans to go off. This extra cooling is useful on a hot day. Looks a bit wierd standing outside your car whilst its rumbling away but never mind!
A trick I use (similar to T88CAN) is if the fans come on key-off I leave it to idle, but I also switch on the heater fan to full and heater control to hot while I wait for the fans to go off. This extra cooling is useful on a hot day. Looks a bit wierd standing outside your car whilst its rumbling away but never mind!
GarryM said:
I'd agree but... if I've been driving in cool conditions and stop (say to fill up with fuel) when I start the car up again it has usually got hotter by about 10 degrees. What's that all about? Usually this is from about 70deg to 80deg and it then maintains 80deg
When you're at a reasonable speed the efficiency of the radiator improves enormously ... BUT the efficiency of the heat transfer to the coolant inside the engine block doesn't change so much. Thus the average temperature of the coolant drops even though the engine block temp is quite high because it can shed heat to the atmosphere very quickly. The oil temp on my Chim gets to its highest sitting in traffic on a hot day, but hacking down a motorway will raise it to pretty similar temperatures. The differential btwn oil temp and coolant temp is at its greatest when you are cruising at high speed.
The ideal solution on any car would be for the electric fans to keep going without the ignition on, it soaks the heat away from the engine via the rad. A few manufacturers do this but it does bring with it reliability issues, fan relays sticking, flat batteries, even under bonnet fires and in the early days alarm problems too. Leaving a car idling may well keep the coolant moving but it also generates more heat, this is why the fans come on in the first place, no airflow. If I have been driving slowly or in traffic I turn the ignition back on after engine off, if the fans come on I leave it on until the fans stop.
Car with Turbos is a different story, you let them idle to allow the Turbo to slow down after a good thrash. Failing to do so means the turbo bearings run with low oil pressure and the oil cooks on them due to the intense heat, hence water cooled turbos.
Ivan
Car with Turbos is a different story, you let them idle to allow the Turbo to slow down after a good thrash. Failing to do so means the turbo bearings run with low oil pressure and the oil cooks on them due to the intense heat, hence water cooled turbos.
Ivan
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