Holden Rodeo Ute 98 TF2.6 L Petrol 4ZE1 when I start the engine I hear water swishing gurgling whistling threw heater fan pipes. It stabilizes, but when i accelerate it comes back under high revs, I changed the water pump and now if worse not as bad, but when the coolant is hot temperature 1/4 on gauge. It doesn't overheat but under revs it still there. Gurgles, swishing noise it drives me Mad ?

Answer: The noise you are describing is air in the cooling system. That is why it is gurgling. The most likely cause is a blown head gasket. When that happens, combustion gases are forced into the coolant and cause air pockets. You may also notice there is no or poor heat coming from the heater.

The reason the gauge does not go up as far as it should is also because of the air pockets. Air around the coolant temperature sensor will not give a true reading the coolants temperature. You need to do a system pressure test to confirm, remove the spark plugs and look for one burning antifreeze, or use a combustion gas detecting dye kit from you local parts store.