Follow the hose from sap out...it goes to the valve...silver thing on exhaust side of engine, with vac hose leaving out the back...assuming, in the UK, you have this pump. The clue, so you know, is that you said the sound disappeared after two minutes...that's how long the SAP runs on cold start, plus or minus a bit.
dmax on the radio--answering all your car questions as best I can!
watsonnwatson.com every Wednesday at 9 p.m. Call in! (661) 449-9340 Click "Watch and Chat"
Please 'friend' me!