I will soon be owning a 1985 300sd. My Mom has done her best to take care of it but I suspect some things have been neglected. I know she has had the oil change regularly and has gotten things fixed as needed. It has 177,000 miles. What are some things I should check when I get this car? How much is a valve adjustment job and when is it needed? How do you know if you need a valve adjustment? I live in Va if that matters. Thank-you.

 

As far as I know those cars are hard to neglect.
Have heard about those engines turning more, than 1/2 milion miles without valve adjustments and even on original injectors.
If the engine never had them done, it would be consideration.
I would do performance testing. Confirm the speedometer with GPS, or road marks and do the acceleration testing. From what I remember, your model suppose to do 0-60 in 17 seconds. If it does and it doesn't burn too much fuel, I wouldn't worry too much about spending money on it.

 

Thanks for the tips. It seems to run fine and causes no problems. A little groan in the front driver;s wheel but that will be getting some attention soon.

 

I think you've got the best. The engine is still having cast head and by 85 MB fixed some glitches with tachometers, cruise control and transmissions.
Enjoy and don't let the car go down. With some rubber and plastic part replacement your children might be happy to inherit it.