Water Pump should be checked
My 87 300E (103 motor) made a squeeking sraping noise as my water pump was going out.
To check WP, grasp the WP pulley firmly with both hands and with about 20-30 lbs force push and pull up and down. If there is any slack felt (more than a very few thousands) or any noise with the slack you probably have a WP bearing going out. The other symptom mine had was occasional water leakage overnight. A small 4-6 inch puddle of water on the garage floor. Soon both the noise increased and the water leaked more.
If yours is replaced; you should also check the serp. belt, the belt tensioner, the tensioner shock and the bushing in the shock. There are a lot of posts on DIY , use a search if you plan to do it yourself. If there is any slack in the tens. shock or the bushing in the shock it will soon break your belt tensioner, (read $$$), so that would create a re-do of most of the labor cost in the WP replacement. Better to do it right than twice, $$$$
Partsshop here has the parts right priced..
but check with your shop to see if they will install your parts purchased here.
Go DIY if you can............Its a little difficult but do-able ........and you have to have some flex sockets and extensions. Read the posts here. Good luck, DanielW