I hate those spring clamps!  Great for saving assembly time in the
factory, but a PITA for the mechanic.  I have had the best success with
channel lock type pliers, also known as plumbing pliers.  The jaws are
angled and there are several slots available for setting the bite gap to
grab the tabs on the spring clamp without slipping off.
Here is a picture of some:
http://www.mscdirect.com/bestbuys/00928564.htm

Throw away the spring clamps when you replace the valve and use screw
type hose clamps.  Once you get the spring clamps slid up off the valve
run a small screwdriver under the hose to loosen it and pull off the old
valve and insert the new one.  You shouldn't lose enough coolant to
require bleeding the system, just check the overflow tank every day for
a week and top it up as it goes down, the system purged the small bubble
introduced in this process itself in my case.

--
Stuart MacMillan
Manager, Case Program
800-909-8244 ext. 8208
Fax: 206-269-6360

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