Abstract: A liquid pressure tensioner for a driving gear mechanism and comprising a liquid pressure unit received within an open cavity of a tubular projecting member that slides along a tubular frame body and has an end portion which engages an endless member of the gear mechanism, the liquid pressure unit including two tubular members slidable relative to each other of which tubular members one member defines a reservoir for storing operating fluid received in a hollow space of the tubular frame body, a high pressure chamber formed between the two tubular members, a conduit for communicating fluid from the reservoir to the high pressure chamber, and a check valve in the conduit for preventing flow of the fluid from the high pressure chamber back to the reservoir.