Cheap & Easy Fix
Yep.Seen a similar problem on my kid bro's car (Kidbenz 1990 190e 1.8).
Damage due to overtightened bolts by dumb tech.
Bought the thermostat cover (plastic) for 8 bucks and took abt 5 minutes.
Loosen big and small hose attached to cover via clamps (one each).Expect some coolant to flow out from the pipes so be prepared.Loosen the 3 retaining bolts on the cover and remove the cover.May take some shaking before it comes out.Replace cover and reverse process.
Top-up coolant as required.
In our case, we swapped out the thermostat as well coz it only cost us another 9 bucks for the part, so what the heck.
Babybenz 1991 190e 1.8