There is a low-budget fix that you can try to revive your WUR.

Remove the large line from the top of the WUR. Use a pick to "fish" the metal mesh filter out of the opening in the WUR. Be sure to get all four layers. Use brake or carb cleaner to blast out any crud or debris in the filter. When you are sure that it's clean, carefully replace it in the WUR and reconnect the line.

If this filter is crudded up, it will keep the control pressure too high, which will make it hard to keep the car running until it warms up. In extreme conditions, where the control pressure approaches system pressure, it can prevent starting.

If this doesn't work, you should probably go for a rebuilt unit unless you can measure control pressure and know how to adjust it. Try Phil at Fastlane or germanstar.net. They are very easy to install.

When is the car overheating? At idle? Does the temp come down when you drive off? All the time? How high does the temp gauge go?

The first line of defense is usually a new thermostat, being sure to "burp" the cooling system when you refill with coolant. You will find several posts on this if you do a Search.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe