Hi all,
Seems like as with many others, I have an engine that over heats at random times, and the cause is unknown. I have had it looked over by two mechanics and neither know the problem. So I have just come to live with it and have spare coolant in the trunk at all times.
My question is, how long can I drive for once the temperature needle hits high and I get a warning that the engine is over heated? Obviously I know I should stop asap but this isn't always possible. One time I was about 1km from home and was wondering if I could just slowly drive home with an over heated engine? Or would the engine blow up?
Also, how long should I usually wait until it's safe to open the coolant cap?
My two cents worth? The ability to drive the car when it’s overheating depends a lot on what the cause is and where you are driving (city or highway). Generally speaking if the car has lost a bit of coolant or the thermostat has stuck shut you can somewhat get around this by turning on the heater if your on the highway with low load and plenty of airflow (speed).
If your accessories belt has snapped and the water pump doesn’t work at all forget about it and get it towed. If your in the city with stop start traffic forget about it and get it towed. If your in a mountainous area where you will be on the throttle a lot forget about it and get it towed.
The heater core is normally further down in the cooling system and will be full of coolant even if the top of the radiator is empty so provided the pump still has some ability to pump coolant around turning on the heater might reduce the temperature sufficiently to make it home.
I‘ve personally done this myself with three different cars. First one was a Subaru Tribeca that cracked the radiator end tank, the second one was my SV6 when the inlet o rings went and I didn’t realise until the the temp started going up (presumably because the pump couldn’t pump sufficient volume anymore as it was partly in air) and the third was with my SSV when the thermostat failed shut. None of them suffered any long term damage.
The important thing is that the temp must go down sufficiently to be kept below the red zone. If the temp keeps climbing or stays in the red zone get it towed.
I know everyone here is going to bang on about blowing head gaskets and hot spots in the head but in my experience this doesn’t happen (at least with my three cars anyway) and I don’t see how it will happen if your gentle with throttle inputs as the available overhead in the cooling system and oil galleries (and thermal transfer in the heads) are made to cope with the cars maximum power output.
For example my SV6 makes 200kw at the flywheel and you only use around 20kw to drive the car at a steady 100kph on the highway so the cooling system capacity required is only 10% on a relatively flat highway. My SV6 was also probably running for a few weeks with hardly any coolant in the top end of the cylinder heads as the o rings would have been leaking for a while and the heads didn’t disintegrate from it (I don’t flog my cars for the most part and rarely go over 3000rpm so this probably has something to do with it).
Again I would like to reiterate that this is just my two cents and my personal opinion and you need to make the judgment call yourself on if your willing to take the risk of doing cylinder head damage from lack of coolant in the cylinder heads vs paying for a tow truck as cylinder head damage is definitely a possibility.