Seat Toledo Diesel Overheating

Sounds like your thermostat is gone. I had a similar problem with my Toledo. Engine was taking ages to warm up, and I noticed the temp gauge creeping up higher than usual sometimes. Check for any coolant leak around the thermostat housing, that's where mine was leaking. Is the coolant level dropping?

Cheers for the quick reply! Coolant level does seem to be dropping slowly, now that you mention it. Where exactly is the thermostat housing located? And how hard is it to check for a coolant leak there?

Coolant dropping and slow warm up pretty much confirms it. The thermostat housing is usually where the top radiator hose connects to the engine. You should be able to see some staining or wetness around it if it's leaking. Honestly, unless you're really comfortable working on cars, I'd recommend taking it to a workshop. Dealing with the cooling system can be tricky, and you don't want to mess anything up. The map thermostat is likely the culprit, it's a common issue, which means the thermostat is defective.

Got my Toledo back from the shop. You were spot on, it was the thermostat! Cost me about 350€ all in. Thanks a bunch for the help!