Idler wheel Cat C9 replacement milage

[Bryan Beamon]

Is there a milage consideration for replacing the idler wheel? On our privious Patriot C7 we had to replace the idler wheel at about 130k. The engine belt configuration is different between the two engines and we now have 140k on our C9 should we consider changing out the idler wheel?

[Gerald Farris]

Bryan,
There is no way to tell when the bearings are going to fail on an serpentine belt idler pulley. On my C 12, I had the bearings fail at 120,000 miles in one of the two idler pulleys, but the other idler pulley and the tensioner pulley are still running at 165,000 miles. I have seen new idler pulleys fail at 40,000 miles. So would I have been better to change both idlers and the tensioner when the first one failed? Who knows, but it is not practical to replace everything on a coach because something might fail. You just have to chose what you are comfortable with, and go with that.

Gerald

[Edward Buker]

Bryan,

Remove the belt and rotate the idler feeling for any lack of smooth rotation caused by bearing wear. It should be silent, a smooth rotation without a change in resistance, and no play. The older they get the more often you should do this check to see if wear is evident.

Cat may be able to give you the useful expected life but it is a function of the build quality, the use conditions, and the age and quality of the grease used. Hard to really predict. They are not overly expensive if you chose to change them preventatively. To reinforce what Gerald is saying I had one show some signs of bearing wear at about 45K miles and the rest have continued on.

Later Ed

[Dave Atherton]

Bryan, Tim sent answer to your question on Ask Dave about add on grease zerk that
will correct problem. This has been a on going problem with on road engines and off road
heavy equipment. Being able to grease hub bearings will prevent failure ahead with
idler pulley. Dave Atherton Retired Cat Mechanic