I had a leaking gasket just above my block heater n the 75. Added some Bars leaks and it took care of it until I finally put a new gasket on.

Look for all the tale tells that everyone is noting i.e pressure in hoses, oil in water, water in oil etc. The thermostat is pretty easy and a cheap fix so you could do this one yourself if you wanted. Really being tested? Go to a second shop and get another opinion without telling them about the first opinion....

__________________
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique