Aluminum timing belt idler pulley??

[Dogger37]

Just purchased a 2005 aveo and with 77,000 miles and it is in need of the timing belt change. I was researching the issues others have had and was wondering if anyone ever found a company that makes an aluminum timing belt idler pulley and water pump pulley to replace the plastic one that seems to fail? Did a search on the forum but didn't find anything.

[SpiffWilkie]

Sorry, nothing to add except for make sure you get that belt changed ASAP. Mine went out about 78,000 or so (the teeth stripped). On the bright side, I have a new head...

[Dogger37]

Thanks for the heads up. I don't plan on driving it until I change the belt, pulleys, and water pump. Plan on changing the thermostat housing as well.

[SpiffWilkie]

Thanks for the heads up. I don't plan on driving it until I change the belt, pulleys, and water pump. Plan on changing the thermostat housing as well.

Good thinking. My thermostat housing split at the seam not long after I replaced the head. It scared me to death seeing all that steam pour out from under the hood. The factory one is a plastic piece of crap and there's a lot of pressure pulling on it.

[zchandran]

I realize that this is an old thread, but the same questions about plastic vs metal pulleys are still coming up regularly.

I first changed my timing belt at 50K miles with a Contitech kit which is on the pricey side. After that, I procrastinated on doing the next change, and finally did it a couple of weeks ago at 130K miles (yeah, yeah... I know). These are the parts with 80K miles of wear on them.

The timing belt looked almost pristine. There was not a single rib with rubber missing, or any cracks, and I would have been comfortable going another 20K miles on it:



Here are the pulley surfaces:




None of these parts have been cleaned. This is exactly how they came out of the car.

As you can see, the surfaces are near perfect and very smooth. I hope this will allay concerns people are having about plastic parts. The bearings are what are critical, and they had zero play after 80K miles. I don't have any paid relationship with Contitech, but I would rather trust one of their kits for 100K miles than a metal pulley set from a small unknown manufacturer.

[northguest47]

zchandran, thats good to hear, i got the same kit on my '06 now (third one)

[petrified.rabbit]

the thing is, zchandran just eluded to it. You want to take the parts off while the still "appear" new. Once they start to look like old, worn parts they can fail. Using broken math, someone who likes math can run the actual figures, If you think of it, the timing belt goes around @ the 1/4 speed as the engine, if you drive at 3000 rpm for an hour, that means the belt rotated 45,000 times. If you drive 20 hours a week, that is 900,000 rotations. In a year that is 46,800,000. In the 5 year recommended time schedule. That is 234,000,000 rotations of the belt. Thats not figures mileage, or any other factors, just run time at an set RPM. So you could almost say since many of us also idle our cars, drive over 3000rpm, and such that belt will have rotated at least 250,000,000 times (for ease of my mental math. The idler and tensioner pulleys are smaller (I'll say about 2/3) then the crank pulley. So they rotates over a billion times before you replace it. 3/2 size x 3000rpm x 60minutes x 20 hours X 52 weeks in a year x 5 years= 1,404,000,000 (calculator says 1.404e9).

Someone who enjoys math can take the gear ratio, and tire size, and add that to my my to *suggest how far you could have travelled in that time. But my math could be if you were just sitting in the driveway running the engine. It does not even include load factors.

With all that in mind, the failure of a plastic pulley is almost never the plastic. It is either the bearing, or heat from the bearing. I have seen the plastic fail on impellers for water pumps, from the chemicals of the coolant eating them away. I have seen melted plastic pulleys, which failed again from heat. Most of the times the plastic buys you time. If the bearing starts to slow down from wear, you should hear it, the belt should slip, thus making the plastic look bad, but an aluminum pulley will just cut the belt.

It all has positives and negatives. Just change the belts at the recommended times. They were engineered with calculations that determine when it should be done. Mileage is still just a guess of rotations, you could have a pulley/timing set with 20k miles have the same number of rations as a car that has travelled 80k miles.