Chain Tensioners.....

[Jase77]

Hi Pelicans,

Is there a recommended length for the pistons on the Hydraulic Chain Tensioners when they are installed?

Mine were 15mm long (installed) and then 18mm long when I had removed them. At first glance both seem to be functioning OK, although one feels a little harder to compress than the other.

Is there any difference in the recommended piston length between the mechanical and hydraulic tensioners?

Cheers,
Jason.

[tharbert]

They can be a little extended, but if tight, should be okay. The driver side idler arm can be close to the top of the chain box but there shouldn't be any sign of contact.

Can you compress the tensioner shafts by hand? They should be very stiff. How do the chain box and ramps look? If all looks good and you have no chain-in-trashcan sounds, button it up and drive.

[Jase77]

Hi Tharbert,

Thanks for your comment. Sorry for the lack of details but I was rushing between meetings.

I am in the depths of an engine rebuild and the tensioners were one of the things that I want to do a closer inspection on. This came into my mind during a very boring meeting, whilst day dreaming and gazing out of the window.

Before the strip down it did sound like a chain in a trash can kind of noise. (Great description btw). The ramps are showing signs of chips and pitting but thankfully the chain case is fine. One chain was slightly tighter than the other but the wear seems even across both chain assemblies. All of this will of course be replaced anyway.

The tensioners look good. Both are very hard to compress by hand and both of the piston lengths were the same when assembled and when removed. I guess the noises were due to the chains being stretched?

I was just wondering if there was a figure that referenced the length of the pistons when they were assembled against the idler etc? Just to use as another fail safe....

[tharbert]

There are threads here where folks have had oil fed Carrera tensioners fail. None describe the position/length of shaft as a diagnosis point.

One of the original Porsche gurus, Jerry Woods, had a web page that described putting a shim inside the Carrera tensioner to keep the tensioner from collapsing due to failure. This shim would do the same thing as those bolt-on collars for non-pressure fed tensioners. Wayne said

"There indeed is a mod that Jerry Woods showed us during his engine rebuild class. It involves taking apart the Carrera chain tensioner and placing a small stop-piece on the bottom. This limits the overall travel of the tensioner and makes it virtually impossible for it to skip a tooth."

If you've heard that sound, I would encourage you to look into something like this mod. That website is long gone. The shim was more like a bronze collar, maybe 3/8" tall, just large enough around to fit in the oil reservoir. Something to consider...

[Jase77]

Tharbert,

Good info and I will do some more research on the chain tensioner assy. If I find anything interesting I will post it up here during my rebuild.

Cheers.