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Re: Timing chain tensioner Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 8 Jun 2007 09:54:17
In Reply to: Timing chain tensioner, saturn, Fri, 8 Jun 2007 09:54:16 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The tensioner is a ratcheting arm with a spring. A little foot sticks out of the tensioner and presses on a guide in the engine that presses on (and tensions) the chain.
The foot is spring loaded to push out, and has a little ratchet mechanism to keep it from being pushed back in. When installed, the foot is pushed pretty close to the body. It exends and presses on the guide, and the tension of the chain stops the tensioner from moving any more. As the chain and guides wear, the chain gets a little longer and looser. Eventually the little arm on the tensioner can push out a little more, and the ratchet keeps it from going back in. This tightens up the chain.
Chains don't stretch, but they do get longer. Each pin and link hole wears just a little, creating some slop. Add that up over each link and pin, and the chain gets longer as it wears.
That's how it works. Now, as to your question-
One sign of a worn chain is that the tensioner is near fully extended. So if the foot is MORE than 11 mm, the chain is loose. If it is LESS than 11mm, the tensioner has more to go, and the chain isn't too long.
There is a very nice set of pictures at http://www.thesaabsite, and look for info on the chain tensioner.
You have to be careful removing the tensioner - mess it up, and it'll extend out and you won't know where it should be. And you can always reset it and stick it back in (and run the engine).
If the tensioner is extended past 11 mm, it isn't a tensioner issue - it's a chain/guide issue.
I don't completely agree with doing a chain replacement based on tensioner extension. Replacing a chain ain't cheap. IF the tensioner was overly extended, I would do more investigation. I would pull the valve cover and actually inspect the chain for wear. You can also turn the engine to TDC for cylinder #1, and see how the marks on the cams line up with the marks on the cam bearing blocks. This is a cheap inspection - about an hour's work, and $25 for a new gasket (less mail order). And chances are your valve cover gasket is leaking oil onto the exhaust manifold anyway.
posted by 192.249....
, Fri, 8 Jun 2007 11:38:04, Fri, 8 Jun 2007 09:54:17 <-- Viewing This Message
, Sun, 10 Jun 2007 08:22:30, Sun, 10 Jun 2007 09:01:19
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