Brown sludge in coolant tank

[ronstakieran]

Heard a pop from the engine and noticed the hose outlet hose from the thermostat had come of managed to get it back on but also noticed a lot of brown sludge in the coolant tank. Next day the car cut out and smoke was coming from the passenger side of the engine. Flushed the radiator and cleaned all the brown sludge from the tank and hoses. When the engine runs the radiator isn't getting warm and the passenger side has a water leak from underneath and its hitting some thing causing it to spit up out of the bonnet. oil in the engine is ok was a bit low but within limits no discolour.
Been told its head gasket by one garage and told by another its thermostat and water pump.
Any advice greatly received..

 

[fixedgear]

If it's the latter it's probably caused the former.

Without a crystal ball it's impossible to say Bert.