For the last few weeks I've been getting an erratic rustling sound. It sounds like it's under the bonnet to the right and forward of the driver's position. (I'm in the UK, right-hand drive). It starts well after the temp gauge has settled on its usual 85deg. When I stop driving to have a look, sod's law, the noise stops. The engine is very hot but dry. It DOES sound like a spluttering/"rustling leaves" sound. It's a bit variable, but I think I can sometimes get the noise to stop by turning up my interior fan and heating very high. Previous to a few weeks ago, the jubilee clip that holds the radiator hose on had been thrown off 3 or 4 times on the open road, resulting in an empty radiator. I now have a very tight clip that has stayed put. I've checked water level as per the manual, so it just covers the visible surface of the expansion chamber when cold. But the day after the funny noises, when I open the radiator filler cap, there's a loud escape of air, and sometimes some coolant bubbles up and out of the neck too. Don't know if these symptoms are relevant to the noises, but I suspect so. I wouldn't say it's losing much water/coolant, maybe just a very little. Any suggestions or help would be much appreciated. If using technical terms, please also use noddy terms, so I can follow you. (There might be a short delay while I find someone who can help me test any ideas.)Many thanks in advance.