Somewhere over the last six months or so I've lost about three pounds max boost. The last couple left after having a new JCW belt and new factory tensioner put in. After seeing a few mentions of slipping belts here, I thought that might be an issue. The car is at the dealer right now for a couple other things, but I asked about the belt tension/tensioner - if the tensioner could be adjusted or out of adjustment. I was told that the newer tensioners are self adjusting, so it should be a "no worry" kind of deal. Could the belt be slipping if the tensioner is working properly?

 

They do adjust the tension via the spring. You shouldn't have to replace the tensioner itself unless it fails though.

See This for checking if you belt/tensioner is within spec

 

Hmmm. The old tensioner was bad, which is why the new one is in there. The guys at the dealer said there was no adjustment on the current ones, though.

 

I was just looking for that pic that CmdrVimes posted in that link. With his help, I can see the entire hole on that tab now.

Do you still have the stock damper pulley on the crankshaft? If so, have the dealer check that as well. We had one in the shop where the crank hub was spinning inside the outer pulley ring. It was driving the techs crazy until they had one guy watch it while another guy revved the engine.
The early dampers are known for having issues.

 

I believe when the Cmdr said "they" he meant the tensioner itself, not the guys in the shop. The tensioner applies constant tension to the belt, so as the belt stretches it instantly takes up the slack and "adjusts" to the belt length.(self-adjusting)
There are no provisions on the tensioner for someone to actually make any adjustment, like CmdrVimes posted, it's done through the spring.

 

oh.


Ah. Gotcha.

 

Now, THAT'S an odd one. I do still have the original stock damper/pulley. I'll ask about that. Thanks.

 

Yeah, that is what I meant.