1985 Bmw318i

My 1985 BMW318I is overheating , I tested the thermostat and looks fine. any other checks?
Also the car does no accelerate more then 40 MPH, what could be this cause?

Thank you

They may be some kind of clog of old oil or something in the motor. You might want to try and change the oil, and check the radiator. Maybe it just needs a tune up.

I used to have a 1985 318i a while back. I had it from 180k miles to 215k miles. Anyway, it overheated every now and then also. But it was because my radiator had a leak. I fixed it eventually and the car stopped overheating. I'm sure you checked that though.

Good luck!