3.5 V8 loosing water from header

All starts runs and drives fine, although can hear sond of running water inside the car though from behind dash area. After about 30-40 mins drive the header bottle warning light flickers and needs topping up. Any ideas please? Oil cap looks clean cant see any water under car either thanks in advance

Mine does that too, but I haven't tried to tackle as everything works OK (including the heater) and I am not using water.

It's air in the cooling system, but there is no specific bleeding procedure as there is on the 3.9 (via the coolant fill tower).

First, with the engine cold, remove the filler plug from the top of the radiator and check the radiator is full. Refit plug.

Half fill the overflow tank, and leave the pressure cap off.

With the heater turned on, run the engine until it reaches normal temperature, keeping the overflow tank topped up. Rev it from time to time to get the water circulating.

Top up the water again then refit the pressure cap.

Good luck.

Pete

There are a few reasons
blocked heater matrix
leaking matrix
Head gasket gone on coolant port to cylinder or a warped head
Coolant pipe split leaking
Manifold gasket
Try pressuresing the coolant system and see where the leak is

thanks, for replies gents. couldnt resist buying it yesterday parked on a driveway near my office, savannah beige with bracken interior, almost in perfect condition and everything working, few bubbles under paint here and there but you have to be looking, last guy used it every day for last 4 years, lady before that then original owner. It even has the original bill of sale from HR Owen in 1988! hoping its not too much of a dog, so far from a pre mot walk round and poke under neath all i can see is a rear bulb, blow on centre exhaust that need addressing for MOT. Sure there will be more but lets see.cheers

ok another minor isse, runs fine, was working on it yesterday and left it running for more than 45 mins no issues. Out the blue today whilst doing a few more jobs it suddenly cut out thought the engine was switched off.
wouldnt restart, had to fire some easy start into the air intake it ran fine for 20 mins and same again. I am yet to fit, leads, plugs, disti arm and cap. does this sound like more of a fuel issue though? any thoughts?