Since nakabili na siya, I think he's now aware of the pitfalls of running without a cap. As an additional advice, I'd suggest he buy a GOOD cap. Kasi yung generic/poor quality caps, bukod sa madali kalawangin ay madali din lumutong yung rubber seal sa neck nung cap. At medyo mahirap po mag-trace ng leak lalo kung nag uumpisa pa lang. Salamat.