Belt dust itself, would have little effect on T-belt. Road dust or silt from river water, is sand. Sand acts as abrasive, which can damage T-belt.
The timing belts covers do a decent job at sealing out dust. But they're certainly not air or water tight. So where driven and how a well covers assembly last time someone did a T-belt service, matters!
I very often find opening from missing bracket for wire hangers. Number one missing, is hanger for cam sensor wire. Shops in a hurry, just rip them out, busting them. They do not take the time to replace and install. This one and others missing, leave opens into belt area.
The timing belts covers do a decent job at sealing out dust. But they're certainly not air or water tight. So where driven and how a well covers assembly last time someone did a T-belt service, matters!
I very often find opening from missing bracket for wire hangers. Number one missing, is hanger for cam sensor wire. Shops in a hurry, just rip them out, busting them. They do not take the time to replace and install. This one and others missing, leave opens into belt area.