If an engine lost all its coolant..

[Shaoxter]

Happened in my M5, coolant level low light came on and steam came out the back. Still managed to make it to the dealer, luckily it was a cold day and a clear A road, oil temp was higher than normal but not more than compared to after a hard hoon.

[Who me ?]

Loss of power. Temp gauge ( sometimes, but not always ) moving high /low. That's my cue to check heater output. The heater will loose heat fast enough for you to stop before any damage is done. BUT, NEVER, NEVER top up coolant with engine off, if engine gets too hot. Let it cool down first, and if urgent, start car with coolant top off, and add coolant SLOWLY with engine running. Ad last, but not least- if temp guage starts to climb - open windows ad run heater as high as possible.

Edited by Who me ? on Sunday 23 November 00:22

[GavinPearson]

If there is no coolant present because of a hose rupture, generally speaking a coolant temperature sensor will not be able to show a loss of coolant - it is being heated by the hot air that now surrounds it and you are more likely to experience engine failure before the gauge shows anything.

On a lot of engines nowadays, engine metal temperature sensors are used. The great thing about these is that they don't get submerged in the coolant, if there is cooling system failure the engine can then be run in such a way that it protects itself - running at lower power and then deactivating fuel injectors so that air is pumped through the engine to protect it. It's far better to do this than rely on the driver to spot a gauge or a light that may not be seen in bright sunlight.

[anonymous-user]

I thought for a moment that the car was on fire before realising that what I at first thought was smoke was steam. The top hose had blown and it was obvious that I needed to stop straight away.

[FD3Si]

It's happened to me twice (both in Mazdas!)
On the MX5, the temperature gauge dropped to zero, due to not being submerged. Pulled over and rad was basically empty.

On the RX7 I had an aftermarket gauge that rocketed(was over 130 when I switched off).
I guess a lot of it depends on whether or not the gauge CTS is in a 'pool' that will collect water if the rest is dumped out?

GavinPearson said:

running at lower power and then deactivating fuel injectors so that air is pumped through the engine to protect it. It's far better to do this than rely on the driver to spot a gauge or a light that may not be seen in bright sunlight.

Wouldn't that make it worse?
In my very limited knowledge of 'this sort of thing' (engines, and them doing magic and stuff) I'd have thought it'd be far more effective to run the engine excessively rich and retard the ignition to reduce combustion chamber temps?
Not saying your wrong, just my take on it - I didn't think that just cycling air would have much of an effect?

[robinessex]

When the top inlet pipe to the rad on my E34 540 snaped off, the resultant explosion of water/steam all over the windscreen gave me a clue all was not well. Stopped immediately. Car transported home, new rad, all was well.

[Monty Python]

I'm pretty sure most cars have a low coolant level warning light - mine certainly does.

[TooMany2cvs]

Monty Python said:

I'm pretty sure most cars have a low coolant level warning light - mine certainly does.

No way "most". Many, yes. Especially more modern and/or high-spec. But "most"? Nope.

[jellypig]

Technically I've never actually have this happen to me.

I did once experience an engine allowing all the coolant to migrate from the cooling jacket to the silencer - so it wasn't "lost" , I knew where it was, it just wasn't where it was supposed to be. And of course the engine was very unhappy having to perform like a sheesha pipe...