530iT M60b30 rattles when hot

[genphreak]

It's common for the main (ie top) roller near the tensioner roller to fail, but they only start to squeak. If the belt is slipping you'll get squeal, that is contamination, wear or a faulty tensioner. It's kinda worth changing the lot in one go, and keeping the parts that are still serviceable as spares jic. That way you know it will all hang together out front for a long time.

[31Hertz]

And the answer is... timing chain lower tensioner piston assembly.
It turns out the A/C tensioner "springer thinger" bushings were worn causing the whole tensioner assembly to angle toward the block. The A/C belt was riding on only half of the pulley. I replaced all of the belts and the "springer thinger." --Then the water pump decided to piss all over the front of the engine. So that + t-stat is new too... I had already installed the metal t-stat housing. However... None of these were the source of the rattle. I pulled out the old tensioner piston, and it had half the spring force as the new unit. I put in the new ass'y and voila! all is well now. NO RATTLE!!! I will now continue to enjoy this car once again.
Thank you all for your kind assistance. Keep on Bimmin y'all!

[632 Regal]

You should systematically go through all the maintenance items. Sounds like the previous owner only replaced items that went bad. Look through the maintenance schedule and replace all belts, hoses, waterpump, bleed the brakes etc etc. Maintenance items are maintenance, not like an old chevy where you only replace broken stuff lol. I went through mine when I got it and do maint as it says, 100k and never any problems.

[genphreak]

x10 to that Jeff. Amen! Hail the Automative Lords, and Burn More Wallet!

Oh- and to the OP: thanks for sharing the final solution.

Those lower AC tensioners are painful- I turned the bolt the wrong way to loosen one before, broke the damned thing... luckily I was obeying Uncle Jeff's 'law' at the time, and I had a new one to replace it with anyhow. It wasn't quite buggered before I got to it. Amazingly, despite the PO's best (or worst) efforts, (i.e. everything (eg nothing) done preventatively by a mechanic with even less of an idea than the guy who was paying him.

I find it helps to think, in the process of buying hundreds of dollars worth of parts to replace all those around something little and cheap that broke, that all these parts ***must*** be replaced at around 'inspection' time, Eg. every 100,000km.

LMAO...