Overheating

[4WDrifter]

The last few times I've had the S2 in a city centre in heavy traffic the temperature, which normally hovers at 90 has climbed up and it starts to overheat. I don't expect that this is normal. Any ideas?

[AndyP]

Is the fan cutting in?

[rynaqui]

How are your coolant levels?

[4WDrifter]

I can hear the fan and levels okay

[rynaqui]

What colour is your coolant, is coolant flowing through all the pipes, any freezing cold weather recently? Radiator condition, is it properly bled? Any noises from the water pump? Just a couple of thoughts

Hope you get it sorted

[macspring]

Two speed fan, working on the second speed ?

Replace the fan switch at the bottom of the rad, relatively inexpensive compared to overheating your engine.

Then thermostat, and then maybe the water pump, if your timing belt is due a change ?

[rynaqui]

Yep, easy to check the switch, undertray off and is visible

[4WDrifter]

Thanks lads I'll get these thing all checked this week.

[quattro-nick]

first I would run the engine warm and check the thermostat
then wait until the cooling fan turns
It is also possible that you have a leaking cylinder head gasket,but then you have to much pressure on your cooling system,the tubes are feeling hard when you squeezes in it
You can perform a leak test on each cylinder
Finally, it may be that your wheel of the water pump has come loose,this must be checking manuel.
good luck

[s2driveruk]

have you changed the coolant recently? Could be as simple as an airlock as they can really drive the temperature. Check the above too and you should find your culprit

[jade]

I have had a problem with my car running hot, I am putting it down to the rad which I have flushed but has not helped, Top of rad is very hot, bottom cooler and not triggering the cooling fan for longer enough it cools lower half fan switches off but top still hot near boiling and lower hose is cool compared to top, In my case I think its the rad as thermostat and circulation seems fine

[chezz]

Citizens beware! the thermostat can be fitted the wrong way around...

[4WDrifter]

If I thought I had air in the system how do you bleed it?

[Rusty]

Cunningly located as a sticky in the engine section

http://www.s2forum.com/forum/showthread.php?t=46952&highlight=bleeding+coolant

There's also the heater matrix, which can be bled when the header tank is lifted up, by loosening off the screw and letting bubble come out until there are none.

The needle normally goes a bit high if there is indeed air in the system or if the system has a leak, which prevents correct pressurisation, e.g. a header tank cap that doesn't seal properly due to the seal getting kinked

[Ross]

How old is the radiator? Any possibility of it mixing different coolant types?

You can empty the rad and see how long it takes a few litres of water to drain through form the top. I had to replace mine as it was blocked when i tested it (after testing the thermostat and water pump was OK). It took about 1min to drain 1l through it rather than about 10s to drain 2-3l through the new one.

Try bleeding it first to ensure no airlocks though; get it up to temp and open the brass bolt on the top of the radiator until it starts to let coolant dribble out. If there's air then it will be bubbling out - wait till its dribbling rather than bubbling and then tighten. Do not over tighten!

If the first fan stage is coming on/off (or staying on if it's overheating) then don't bother replacing the switch, it's working. In this climate stage 1 for about 10s every couple of mins should keep it around 90. Since flushing my system and replacing the rad, it sits at 88/89 without the fan at all. I have to take it for a quick thrash then pull up for a minute to get it to kick in. If the rad is blocked, you'll notice the rad is cooler at the bottom too which may make fan control a bit erratic.