Could be an air lock, if you rev the car when its up to temp does the heater suddenly blow hot air?
I doubt its the pipes from hell, I've had mine done at huge expense as I was told these by a Toyota tool/fitter and it turned out to be a lose hose spotted by proper mechanics.

If you're concerned it might be the pipes then take off the under trays and check em out.

It will be easy to spot a leak with the car up to temp.

Toyota charge upwards of

£1000 for replacement pipes fitted, an independent I'm guessing will charge 5-600 but as I said its more likely to be an air lock or screwed rad, rad cap, water pump, thermostat or simply a lose hose.

All these need checking 1st.
