I have a 1994 toyota camry v6 and it has a fluid driven cooling fan not electric.why is my hydraulic driven fan spinning so slow while idling . Over heats when sitting in traffic. I took it to a shop and they block tested the radiator , added 1 gallon of coolant and told me the fan is not spinning . They could grab onto the fan while engine was running . They said it doesn't have a blown head gasket . They test drove and said it ran fine . When I was driving home from the shop it started to overheat again . Help

It's run off the power steering system. Never liked it. But first thing I'd check, see if the small electrical connector is connected to the power steering pump.
Common this is left off after timing belt or valve cover gasket jobs.
The fan won't speed up without it connected.