Fits those chassis models from 1981 to 1991 that have a coolant reservoir tank ( see details below )
Replace your old worn and weak expansion tank cap to eliminate minor coolant loss problems. Watch the video below as Kent will explain the difference in caps and why you want to make sure you purchase the correct one.
R107 W123 W126 Coolant Reservoir Tank Cap 120 degrees
$10.50
SKU:
GEG-COMRETC 
Product Details
Related Products:
$10.75
Special Radiator Cap Only for Older Models with Cap on Radiator
Fits most models from 1973 to 1983 with cap neck located on the top of the radiator.
If you are experiencing minor coolant loss on your older model that has the cap on the radiator, it may because you do not have the correct cap. Not all caps are created equal as Kent will point out in the video below:
This is the type of radiator that will require this cap.