Pulling the thermostat housing is not difficult and the only sure way to make sure the hose gets seated top and bottom. All the hoses and belts should be inspected by you ( perhaps while you are changing your oil) and these items need to be replaced as a matter of routine PREVENTATIVE MAINTENANCE .
"If it ain't broke, don't fix it" is the call of the idiot. It also keeps tow trucks and mechanic shops in business.

__________________
You can get farther with a smile and a gun than you can with just a smile.

1984 300D
1985 300CD
1980 300SD
1993 SL500