AFAIK, walang goma ang solenoid.

It is primarily a a loop of wire, often wrapped around a metallic core, which produces a magnetic field (hehe, galing wikipedia yang definition na yan).

Nagloloko pa VTEC mo? VTEC kasi won't engage when the oil pressure is low, among other factors. Baka yung leak is galing sa engine mismo, tumatapon lang sa solenoid. Gawa ka ng VTEC light to find out! Pero mararamdaman mo din naman kung nag-eengage ang VTEC by the rumble of the engine (for SOHC VTEC-E engines, 2.2k rpm ang engagement point)