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Re: Timing Chain at 91,000 Miles? Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 25 Mar 2002 13:29:55
In Reply to: Timing Chain at 91,000 Miles?, Nate, Sun, 24 Mar 2002 15:32:14 Members do not see ads below this line. - Help Keep This Site Online - Signup |
There is no maintenance interval for a timing chain. With regular oil changes, and except for a few cases, a timing chain should last the life of the car, well over 200K miles. The few cases are where a chain may have been weak to start with from the factory. But 91K sounds early.
The next point - and I'll get on my soapbox for this one - is that no reputable mechanic should EVER diagnose a timing chain by sound alone. There are occasions where you know there is a timing chain problem by sound - imagine a coffee can filled with silverware rolling down stairs. I'll bet your engine is more of a fast tapping, not a china closet collapsing.
There are a lot of things that make tapping noises at idle, and the timing chain is only one of them. Fuel injectors, worn fuel damper, or a lazy lifter all tap with engine speed, and are noticeable at idle.
Try a few things first. Do an oil change. Sometimes that quiets things down. Next, manually turn the engine BACKWARDS a couple of turns. If your car is a manual, put it in 5th gear on a flat piece of ground and push the car backwardsa dozen feet or so. Or, pull the spark plugs and throw a wrench on the main pulley bolt and turn the engine backwards. You pull the plugs to eliminate any resistance from engine compression. This can reset the chain tensioner. The tensioner is a ratcheting mechanism, and you might be on the hairy edge before it ratchets out a little more tensioning. Turning the engine backwards can do the trick.
Lastly, if you're really worried, inspect the chain. I would NEVER replace a chain without inspecting it first. For the price of a chain job, the inspection is cheap. All you do is pull the valve cover and visually inspect the chain. Does it look worn? Do the cam sprockets look worn? Next, turn the engine over to TDC for cylinder #1, and check the alignment marks on the cam against the marks on the head. If they line up, the chain hasn't 'stretched'. If they don't line up, then suspect a worn chain. Chains don't stretch, but over time and without proper lubrication, there is wear between the pins in the chain and the holes they go through in the links. A few thousands of an inch of metal wear from the pins and the holes. Add that up over all the pins and holes in the chain, and the chain gets a little longer. That is a 'stretched' chain. The extra length isn't a problem, but if there is wear at the pins and holes, then the chances of breakage increase.
If the chain looks good and the marks line up, the chain is probably just fine. Spend $25 and replace the chain guide mounted in the top of the valve cover, because it's so accessable. Add $20 or so bucks for the cost of a valve cover gasket, and you've invested less than $50 and an hour's worth of work to KNOW if your chain needs work. And I'll bet your valve cover gasket is already weeping a little oil onto the exhaust manifold.
I've had numerous dealerships tell me the timing chain in my older 9000 - a '88 - is ready to pop. I've heard that story for over 5 years and 60K miles now. The last time I inspected the chain - a little over a year ago - it looked just fine. Yes, the engine rattles when cold, and is rattly at idle. But the chain shows no appreciable wear at 140K.
Good luck!
posted by 140.157....
, Mon, 25 Mar 2002 13:29:55 <-- Viewing This Message
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