To test the water control valve, one doesn't need or want to disaasemble it. What are you going to do then.

To test it one needs to evaluate its performance or by=pass it so to speek. Do you need more heat, pull the thing out and place a straight pipe in. Did you get more heat?

Do you want less heat? Block it!. THe easiest way is to clamp off either the inlet or the outlet hose with a clamp (I use a visegrip with an extra piece of hose material to protect the cars hose from the vicegrip teeth).

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician