I'm trying to disconnect a heater hose from the quick-release coolant stub located at the right rear inlet manifold corner. The purpose is to access the engine coolant temperature sensor located beneath the coolant stub. I have tried using pliers to depress the two plastic tabs on the stub connection but to no avail. Thanks.

Had the same issue. Trick is to squeeze the inner rather than the outer (white bit instead og black bit) whilst keeping tension on the hose to release it. Hope that makes sense.