Timing belt tensioner
Discussion
What's the best way to determine the condition of the tensioner bearings? When the car starts cold there is a clacking sound that concerns me. It lessens as it warms up. I thought the alternator's bearings were going bad but when it was replaced it, the sound continued. The tensioner is so far forward and against the firewall I can't even see it, any suggestions on how to examine it?
91 SE thanks
91 SE thanks
Scotto97 said:
What's the best way to determine the condition of the tensioner bearings? When the car starts cold there is a clacking sound that concerns me. It lessens as it warms up. I thought the alternator's bearings were going bad but when it was replaced it, the sound continued. The tensioner is so far forward and against the firewall I can't even see it, any suggestions on how to examine it?
91 SE thanks
Scott,
Without removing the tensioner, it will be nearly impossible to gauge the condition of the bearing. Truth is, if in doubt, replace it. This is not a part you want to wait to address until it fails. While a failure may sometimes be progressive, it could totally fail at any time and so at the 1st suspicion that something's wrong, you should replace it. Difficult, moderately spendy to be sure, but only half so when compared to the consequential damage of a total failure. If addressing, don't forget the timing belt, and are you ready for valve shimming yet?
That said, given the symptoms you describe, you also need to rule out the mechanical vacuum pump mounted on the left front side of the engine. These too can make a chirping or clacking sound once it's bearing has started to go. With the engine idling, kneel or lay next to the left hand side and see if you can better locate the sound. Then try the right side, does the noise seem further away? If so, it may be the vac pump.
Happy Motoring! ...Jim'85TE
The 'clacking' sound you are describing reminds me of the 'slapping' sound I've heard/watched too many times before.
What I witnessed first hand was the timing belt oscillating just before it jumped a few teeth and killed my engine! Obviously, I was in a hurry and didn't tension the belt properly and it cost me dearly.
The tensioner bearings are sealed and it is very rare that they fail. What happens much more often is that time the belt stretches beyond the ability of the tensioner to compensate.
The belt is most loose when on a cold engine. As the engine warms up the aluminum expands slightly, and the nylon in the belt contracts, tightening everything up. A loose timing belt is hard to diagnose on a warm engine. 907's are famous for cold-start belt jumpings because they have fixed tensioners.
Make a point of checking the timing belt slack every time you check the oil (preferrably when cold). If it deflects more than ~1/2" (between the Accessory and Intake sprockets), it may need adjustment.
What I witnessed first hand was the timing belt oscillating just before it jumped a few teeth and killed my engine! Obviously, I was in a hurry and didn't tension the belt properly and it cost me dearly.
The tensioner bearings are sealed and it is very rare that they fail. What happens much more often is that time the belt stretches beyond the ability of the tensioner to compensate.
The belt is most loose when on a cold engine. As the engine warms up the aluminum expands slightly, and the nylon in the belt contracts, tightening everything up. A loose timing belt is hard to diagnose on a warm engine. 907's are famous for cold-start belt jumpings because they have fixed tensioners.
Make a point of checking the timing belt slack every time you check the oil (preferrably when cold). If it deflects more than ~1/2" (between the Accessory and Intake sprockets), it may need adjustment.
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