Overheating in traffic

[sparrow77]

So, as the title says, my pug is getting up to around 105-110c while stopped in traffic, even for a short while. It's never gone above that but I fear someday it might... Normally the cooling fan kicks in around 95-100c and stays on for long periods of time, usually because the temperature fails to fall below 90-95c unless I get on the motorway. I've been reading about the fan having a default slow setting? I suspect my fan is off all the time, then comes on full blast when it needs to - is this the norm on non-A/C cars or should it be constantly running on the 6v slow speed?

The car is a 1998 1.8 16v, no A/C. I changed the thermostat and the coolant last autumn as it was doing it back then as well, then it was fine for most of the winter (we average about -10 degrees here in Finland most of the winter so I'm sure that helped), but now it's started again as the days have gotten much warmer.

Any advice? Relay problems? Could a leaking head gasket cause overheating issues? There's oil on the front side of the head (viewed from the front of the car) that's been there for a while and I keep finding tiny deposits of oil on and around the motor... so there's that.

[rwb]

The no low speed thing sounds plausible. Definitely check the relays, I've seen them literally disintegrate on much newer cars.
There's a wiring diagram for them somewhere on here...

[steve_earwig]

Not for a D8 with no a/c and one fan they're ain't. I'm pretty certain it means you only get one speed, with two fans the pressostat runs them in series for half-speed but no air con = no pressostat, therefore no half speed.

I doubt it means trouble with the head gasket, unless you're loosing coolant. Maybe the fan thermostat is going deaf in its old age, or as it takes a while to drop the temperature the radiator is blocked up with crud

[Doggy]

Worth making sure there's no air trapped in the cooling system to 'fool' the sensor(s)?

[steve_earwig]

Good point The sender for the gauge and the switch for the fan will be two different things so worth checking.

[Bailes1992]

My first port of call would be to make sure your fan has all it's fins! If it had then I personally would replace the temperature sensors. Make sure you are getting the right readings.

[Rolebama]

I would suspect the motor. A 15/16 year old fan motor is most likely down on power, and maybe not shifting enough air to do the job.
A secondary thought; maybe the radiator is partially clogged and the air can't pass through the fins efficiently.