Overheating in traffic. At what point do I switch off?

Archeron

I've got my car booked in to get an overheating-while-stopped-in-traffic issue sorted this saturday, but in the meantime, I need the car for work. I pray i dont hit a tailback, but of course this morning I did.
Normally, the temperature guage sits just under half way between cold and hot. Now though, as I am stopped, it begins to creep ever closer to the H end of the scale. As soon as I start moving again, the cold air intake cools it back down.
What I'm wondering is, at what point should I just pull in somewhere safe and switch the engine off to let it cool down? Would it be safe to continue driving if it reaces 3/4 of the way up, or even more? Unfortunately, there is nothing other than just C and H to give an idea of how hot it actually is, so its hard to know what temperature its reached, but as soon as I see it pass the half way mark, I just start getting paranoid. Its a 1991 car as well, if that has any affect on how hot it can get.
thanks.

Ice_Box

Try turning the heater and the fans up to the last and open the windows. Used to work in my old vectra. The temp would drop after 30 seconds.

Archeron

Ice_Box wrote: »

Try turning the heater and the fans up to the last and open the windows. Used to work in my old vectra. The temp would drop after 30 seconds.

Yeah, thanks Ice Box. I have been doing this and it does work when stopped at lights or the like, but tailbacks on motorways seem to heat it up regardless.
I had a lovely boiled red face when I got into work this morning

Rovi

Ballpark guesstimate: don't let it go past around 1/4 of the gauge above normal.
Does that make sense?
What I mean is, if the needle normally sits at half way up the gauge, don't let it go above three quarters
If the gauge is reasonably well matched to the engine, this should give some leeway before the temperature gets so high as to do damage.

Obviously, try to use a route that results in the least amount of time sitting stationary, and turn the cabin heater on full to add more cooling to the system.

thewools

Ice_Box wrote: »

Try turning the heater and the fans up to the last and open the windows. Used to work in my old vectra. The temp would drop after 30 seconds.

See above - will help...

Engine coolant? just have a check and top up if required...

if this not the problem your radiator could be knackered...

Archeron

Thanks for replies all.
I think my fan sensor switch is fecked as the fans dont seem to switch on. Though I have also had bothers with a leak in the rad, a leak in the tank and leaky hoses, so I'm going to let the mechanic have a good nose around in there on Saturday.
Thankfully 90% of the journey is deserted back roads, its just the approach into Dublin that worries me.

Avns1s

Can you bypass the switch so that your fan is running all the time until your mechanic has a look??

Better to have a bit of energy wastage (miniscule) than have an overheated engine.

BrianD3

On the motorway drive fairly slowly in top gear (eg 50 mph) and keep the heater on full blast and windows open at all times. Also turn the heater on full blast immediately when you start the car from cold, you may finish your journey before the car even reaches operating temp.

People often think that the faster you drive the better the cooling, this is true to an extent but if you have say a blocked radiator or dodgy water pump or some other problem affecting coolant flow, the air rushing over the rad at high speed will be "wasted". And at the same time the engine will be producing a lot of heat due to the high revs at high speed.

edit: I know your car is overheating in traffic but if you can keep it as cool as possible while driving along then it will be cooler when you do hit traffic which will buy you some extra time.

alias no.9

Some cars use a thermocouple, located in the thermostat, to send a signal to the fan to switch on / off. If you unplug the connector at the thermostat, it causes the fan to stay permanently on. You can check this very quickly if you're clued in under the bonnet. The same thermocouple can often be used to send the signal to the temperature gauge, so when it's unplugged the temperature will read off the scale. If you're confident the reason it's overheating is simply the fact the fan isn't cutting in, and you can switch the fan on by unplugging this, leave it unpluged to keep the fan permanently on. If you suspect there may be another underlying cause, leaving it unplugged is too big a risk since without the temperature gauge, you've got no warning when it's overheating.

testicle

thewools wrote: »

if this not the problem your radiator could be knackered...

Or the water pump...