You can also use the old style monovalve and loop the coolant line. My mechanic did it when I installed a veggie tank in trunk.

The old type is much cheaper and not prone to cracking. You will have some minor flutuations in coolant temperature but in the three years I've been running with one, have never had a problem.

__________________
-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991