I recently had my engine swapped onto a new chassis and body. (80' 240D) the new chassis has a like new radiator. i had a thermostat on the engine that i had drilled open to let it cool a little better for the old set-up. on the new set up it was staying real cold so i put a new undrilled thermo on it and it still barely breaks 80 C in still traffic and colder on the highway. my guess is that its a problem with the connection in wiring. i didn't do the engine swap so where should i look next.