Polo running cold

[Bristol Boy]

I recently bought a 1997 Polo 1.4 (AEX engine), and the temperature gauge takes forever to even reach 70. But today, after a fast 20-mile run (with gauge eventually showing 70 after the first 10 miles) I left it to idle for a couple of minutes - and the gauge rose to the middle of the scale (around 90?), where I'd normally expect to see it ALL the time (after 2 or 3 miles to warm up)!

Top and bottom radiator hoses are fairly hot, but not too hot to hold for half a minute (ie not scalding). In-car heating seems to work fine - nice and hot.

There is also mayo in the oil filler cap, but no oil in the coolant. So I'm hoping the mayo is caused by the "cold" engine not evaporating-off the condensation in the engine - not a blown head gasket (pleeeease!!!).

I'm thinking it must be the thermostat sticking open. But why would the gauge rise to 90 when idling? It surely can't be down to the very cold weather we've got at the moment keeping the engine cold whilst driving, then letting it warm up once the air movement stops, can it?

Has anyone got any ideas?

[dragon_green]

In the winter, mine used to show the needle under the halfway point when on the motorway. Can't remember if it rose when idling though.

[bstardchild]

I'm thinking it must be the thermostat sticking open. But why would the gauge rise to 90 when idling? It surely can't be down to the very cold weather we've got at the moment keeping the engine cold whilst driving, then letting it warm up once the air movement stops, can it?

Has anyone got any ideas?

No air flow thro rad at idle when stationary - engine gets hotter

Loads of air flowing thro rad when driving depressed temp is thermostat is fugged

[Bristol Boy]

Thanks guys. I'll swap the thermostat and see if that improves things.