Lexus RX Hybrid Belt Tensioner Failure

A defective belt tensioner on a Lexus RX hybrid, eh? I had a similar issue on my previous car, though it was a different make. Back then, the engine started making this awful screeching noise, and I noticed a decline in engine performance. I eventually traced it back to a faulty idler pulley. Before you jump to conclusions about the belt handover, have you thoroughly checked the tensioner pulley for any signs of wear or damage? Also, is there any unusual engine noise when the car is running? Keep in mind that without proper tension, the belt can slip, and this could be perceived as a 'handover' problem. If you can rule those things out, then we can consider a defective belt handover itself.

I haven't noticed any unusual engine noises, but I'll double-check the tensioner pulley. What specific signs of wear should I be looking for?

Okay, no unusual engine noises are a positive sign. When inspecting the tensioner pulley, look for wobbling, cracks, or any play in the bearing. Also, observe the belt itself. Is it properly aligned? Is there any visible damage, such as fraying or cracking? Excessive belt dust around the pulleys is also a telltale sign of a problem. If everything appears normal upon visual inspection, it's entirely possible that the belt handover mechanism is indeed the culprit. Given the complexity of a hybrid system, and your description, I would strongly recommend taking it to a reputable workshop. They'll have the diagnostic tools and expertise to pinpoint the exact issue and recommend the appropriate repair. The price in the end was around 455€. It’s better to be cautious.

Thanks for the detailed advice. I appreciate you sharing your past experience. I'll take it to a workshop as suggested. It turned out the belt tensioner was indeed defective, as suspected.