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Uh, no Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Sat, 11 Feb 2006 18:09:46 In Reply to: timing chain, Per Soderlind, Sat, 11 Feb 2006 15:01:06 Members do not see ads below this line. - Help Keep This Site Online - Signup |
There is no recommended replacement interval for the timing chain. It is only replaced 'on condition' - that is, if it wears out. However, when you change the oil regularly at a reasonable interval - 3-5K miles, it should last forever. I've run a few Saab 4-cylinder engines into the upper 100K range, and the timing chains were doing just fine.
The timing chain itself can be replaced for a few hundred dollars. There is a method called 'rolling in' where the valve cover is removed, a chain link removed, and the engine turned. As the new chain rolls in, the old chain rolls out.
However, I'm not a big fan of this method. Chains don't wear out by themselves. They run on gears, and have chain guides. To replace all the parts - chain, gears, and guides, requires removing of the timing chain cover, which is a lot of work. Assume on the order of $1200. But as said before, this is a very unusual condition.
OK, how do you know the chain needs replacement? "It sounds bad" is a very, very bad method. Saab engines tend to be rattly. Yes, if the engine sounds like a tin can of silverware rolling down stairs, the chain may have an issue. But if one is worried, simply remove the valve cover. Seeing as the valve cover gasket usually starts leaking after a few years, the valve cover comes off. You can visually inspect the chain for wear. You can also turn the engine so cylinder #1 is at TDC, and you can see how the marks on the cam sprockets line up with marks on the head. If they look OK, the chain is OK.
Another method is to see how far extended the chain tensioner is extended. Saab even states this is the accepted method. If the tensioner is too far extended, it implies the chain has worn. I'm not a big fan of this method, either. I think Saab uses it because it's pretty simple. If I'm thinking I may have to invest over a grand for the timing chain, I'll spend the $25 for a new valve cover gasket and inspect the chain.
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