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timing belt tension

I have a pretty standard timing belt setup; two gears, a water pump, and a tensioner/idler. I was talking to someone and timing belts came up. I mentioned that after replacing my timing belt, if I stood near the belt and had someone hit the gas, I could hear a faint "whorling" from under the timing cover that I didn't recognize from before. I have an idea what a too-tight timing belt sounds like, and thought that I may have gotten it on a little tight, but nothing too serious because of the low volume of the noise. Well, this fellow disagreed and said that any noise coming from that area was the bearings under stress, and thus a timing belt that is on even a little too tight is going to shorten the life of the camshaft and water pump bearings as well as the timing belt.

Is he right? Are the bearings the source of the "whorling" noise?

Does any noise at all from the timing belt area imply a shortened belt life? What about bearings?

Is the (presumed) shortened bearing life due to heat from excess friction, or due to the shafts spinning slightly out of round from the belt pulling on them?

To be more precise with setting the belt tension, is it safe, as this fellow says, to apply tension to the belt with the engine running and idling? That way the noise would be immediately detectable. I did the best I could measuring the belt deflection with the engine off. Honestly though, I was guessing at the force to check the belt deflection since I knew of no way to precisely create the force quoted in the shop manual. I just pressed on a floor scale to obtain the number and then tried to press exactly that hard on the belt.

When tensioning it my overall strategy was to try to get it to the point where the tension was minimized but where there was no back and forth play in the belt as I turned the crank, and I believe I succeeded there.

Or maybe new belts make noise as they break in. I've never done one on my car before so I wouldn't know. It is a Gates belt. I do have a new tensioner.

Reply to
Ryan Underwood
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Doesn't your car have an automatic tensioner?

Reply to
« Paul »

I don't think engines have "automatic" tensioners for cog type timing belts. I've had cars that used a spring to set the initial tension, but after manually turning the engine over a couple of time to eliminate the slack, you lock down the tensioned with a bolt. The problem with these is that the proper tension for a new belt is different from the proper tension for a used belt. A spring loaded tensioner like the type used with the multi-vee accessory drive belts can't be a good idea. Too much chance of the belt jumping timing. I have also seen procedures that called for the use of a special tension gage for setting the tension. But on most of the cars I have owned that had belts just specified a certain deflection under thumb pressure (or in some cases a specified pressure) at a specified point. Timing belts do stretch slightly after installation, so even if it whines initially, this may stop after a few miles. However, in general, I think a whine is a bad sign. Excessive tension may overload the tensioner bearing and lead to early failure of the tensioner. The load on the main and cam bearings is not likely to be a problem (at least to the load on the tensioner).

Ed

Reply to
C. E. White

on mine, both idler bearings made a noise when turned by hand, so I replaced with new mine has a spring on the tensioner pulley, then a lock down bolt, I pulled upward with a large hook tool, smoothly but with a lot of force (enough to move the whole engine) to tension the belt (or you could use a pry bar at the tensioner), then let the spring hold it in position while tightening the bolt. I also have a Burroughs belt tension gauge (easy to be 20, 30 or even

40 pounds off without a gauge if a belt takes 100 lbs.), plus you can probably find an inexpensive "click type" small belt tension gauge at NAPA good for smaller belts up to 100 lbs.
Reply to
nospampls2002

No, it's a manual tensioner. Were it an automatic or a pressure-driven tensioner, would there be any question? :)

Reply to
Ryan Underwood

Oh, that's a good idea. Thanks.

Reply to
Ryan Underwood

True. What engine are you working on? I am familiar with GM and some imports but not much else.

Reply to
« Paul »

They are used. Toyota and Mitsubishi come to mind, but there are other instances. Automatic tensioners are constructed of a steel or aluminum cylinder with a spring loaded, hydraulically damped piston which applies pressure on the tensioner pulley frame - which itself is mounted on a pivot. There are usually a series of pinholes in the housing and the piston so that, when compressed, the tensioner can be pinned in position to make installation easier. The pin is removed once all of the timing components are in place; then the piston expands quickly to apply pressure to the tensioner pulley.

Toyota MDT in MO

Reply to
Comboverfish

If your belt uses a manual tensioner or no tensioner, try the method recommended by VW: pinch the belt midway its longest span and twist it. When the tension is right for a timing belt you should be able to twist it almost exactly 90 degrees. I don't know if this method works with automatic tensioners.

Reply to
do_not_spam_me

How does this account for people with different hand strength?

--------------- Alex

Reply to
Alex Rodriguez

Probably anyone that can r&r a timing belt has pretty good hand strength.

Reply to
« Paul »

Isuzu 4XE1 SOHC.

Reply to
Ryan Underwood
[snip>

Aahh! Do you by chance have the service documentation for the Isuzu 4BE1 engine? Until I haven't been able to find that one, although I 'desperately' need it.

shakiro

Reply to
shakiro

Ok. Thanks. I am not familiar with it at all.

Reply to
« Paul »

No, sorry. But you can ask on

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- the people there aregenerally rather helpful.

Reply to
Ryan Underwood

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