Allion Overheating Map Thermostat Suspected

I had a similar problem with my Allion. Does the temperature gauge fluctuate a lot, or stay consistently high? Have you checked the temperature sensor? It might be worth looking into the map thermostat; a defective one can cause those exact symptoms.

The temperature gauge stays pretty high once it eventually warms up. Where is the map thermostat located, and is it easy to check or replace?

On my Allion, the map thermostat was integrated into the thermostat housing. While you could technically check its electrical connections, given your symptoms, a defective motor within the thermostat cooling circuit is highly probable. In my experience, it is usually the case. I would recommend getting it checked by a workshop to confirm and avoid potential further damage.

I took it to a workshop, and you were right it was the map thermostat. The replacement cost around 350€. Engine is running fine now. Appreciate the help!