Saab Central - Technical Help
Classic Saab 900: Checking wear on the timing chain
Article by P.Whiter, 1990 900i 16v
The symptoms of a worn timing chain can vary, but in my experience the early symptoms include a rattling noise upon starting the engine from cold which gradually recedes as the engine reaches operating temperature. It is fairly straightforward to check the wear on the chain so if you suspect your timing chain is nearing the end of its life then read on.....
You can see from the picture on the left where the timing chain tensioner is located, NB this article only covers the later type chain tensioner, it is easy to identify which type of tensioner you have.(See below)
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| New Type Tensioner | Old Type Tensioner |
Presuming you have the new type tensioner you need to remove the 12mm bolt on the top of the tensioner body, (this releases the pressure on the tensioner) as you remove the bolt be careful not to drop the spring and small plastic insert that will come out with the bolt. Also do not lose the rubber O-ring that seals the centre bolt to the body, it is probably a good idea to use a new O-ring here if possible.
Now you need to remove the tensioner body itself, I can't remember the socket size but it is approx. 24mm, be careful not to press the pushrod back into the Tensioner body, as the next step is to measure the extension of the pushrod from the tensioner body.
As you can see from the picture on the right you need to measure from the end of the T/body to the inside of the lip on the pushrod. Under no circumstances should this measurement exceed 11mm. If it does you need to replace the timing chain, (The tensioner does not need to be replaced)
To refit the tensioner the first thing to do is reset the pushrod by pushing down on the ratchet and at the same time pushing the pushrod back into the Tensioner body (picture right). Then fit a new seal before refitting the Tensioner body, This should be torqued to 63Nm (47 ft. lb.) Place the plastic insert and spring in the hole in the Tensioner body and after refitting the O-ring refit the 12mm centre bolt. This should be torqued to 22Nm (16 ft. lb.). As the plug is being tightened the spring pushes the pushrod and re-tensions the timing chain.
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Classic Saab 900
