what`s it for?
 

It drives the hot coolant to the heater core.

Thanks for the response. I guess it should have hoses attached, can you tell me where the other end should go? It is on my 1990 190E 2.6 Thanks again, wayne, aka- brokebutt

After the pump, there should be a fairly large tube that goes along the exhaust side of the engine bay, through the first firewall and then connects to the heater valve at the second firewall that separates the engine bay from the interior, just off the center of the windsheild glass.

most other cars get the push from the water pump......Benz needs to give it a push with an external pump....

The aux water pump works in conjunction with main engine water pump, but mainly this is a convenience feature: It does two things: on all cars it regulates flow: at idle or when stopped in gear, with low engine RPM's, it keeps full circulation so the heat stays hot. When you gun the car away from a stop, it works with a monovalve so you don't get a sudden blast of hot heat. The other thing it does it runs the "rest" function. When the engine is off, it helps circulate still-hot coolant for up to 30 minutes so you can have heat even after the car is off.
If people have problems with this, they just bypass the unit and let the main water pump do its job. One thing to note, however, is when the engine starts to overheat this extra pump can help cool the coolant quickly.

Thanks
 

Before I had ever even looked at this forum, I heard there were some great people here.Thanks to all. I`m sure I`ll have some other things pop up in the future. Until then, I`ll just come along for the ride.
Wayne aka brokebutt