Hi,

how much degrees did the engine get?

Be careful with the screws of the thermostat - it's usual that you don't get them out after 20 years or more and you may end up in drilling new holes and making new windings. Put a lot of rust remover on it and let it react long enough. And yes, in that case it would make sense to remove some more parts to get the right force to lose the screws.

Still, I'm pretty sure the radiator is your problem... but it's not that cheap at all.

Bastian

Das Buch zum Audi V8