Series 3 Timing Chain Tensioner

[Moritz]

Hello. My recently rebuilt Series 3 engine had some bad clattering at idle, I narrowed it down with a stethoscope to the timing chain area and at this point things are opened up and I have been fiddling with the tensioner. First, the idler gears are not sufficiently extended to put any pressure on the chain (encouraging). Second, with the ratchet moved up/out of the way, I could not move the mechanism in or out against the spring (confusing). It felt locked in place for some reason. So I removed the ratchet mechanism, and pulled the fixings for the tensioner. As I pulled it away from the block there was a squeaking sound (some sort of pressure release) and voila...I could move the mechanism up and down against the spring.

So, questions. 1) What does the no-return valve on the "piston" do? Presume I may have an obstruction in the port to the block the mechanism is bolted against. My next step would likely be cleaning everything in gasoline and blowing some carb cleaner into said port, removing the no-return valve ball and spring and cleaning that. 2) Am I missing something? Been following the green book so far, but it seems silent on this bit of confusion.

UPDATE/CLARIFICATION: Once the pressure (or vacuum) was released, the tensioner extends enough to put the chain under tension (with the spring). It was like there was a vacuum in the "piston" strong enough to prevent the spring from pushing the idler gears out, yet enough pressure to keep me from moving the assembly against the spring with my finger.

Weird

Thanks

Richard M.
'74 Series III