Could be a failing water pump (hopefully). My E46 always had a rattle, which I thought was the usual VANOS rattle, but it turns out it was the water pump.


It could also be the AC pulley bearing. Search around. There's a good thread that discusses it, and a great youtube video walking through the replacement.


Edit: Here's the youtube video https://www.youtube.com/watch?v=5qd0e-vVxQA

Unfortunately couldn't poke around much yesterday. Got home late and working late today and tomorrow. I ordered the parts hoping my gut feeling is right. And again coolant system work is likely due anyways.

When I tear into it I'll be able to diagnose if it's another pulley or anything and proceed from there.

Doing WP, thermostat, belts, #1, #2, and #5 hose, and return pipe.

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I think that's a good approach. Also, you may know this, but the crank dampener pulley has to come off to replace the water pump. It's held on by (I believe) 8 torx-head bolts.

Apologies, but if it hasn't been said already and it hasn't already been done, it's inexpensive enough to replace the tensioner and idler pulleys while you're in there also. And yes as Entropy mentioned, the crank pulley has to come off and it is torx bolts - I would suggest soaking them in liquid wrench and letting them sit for a bit before wrenching on them, they're easy enough to get to with the fan out but man I'd hate to break one if you had one stick... and be sure to line up the little guide "pin" when you're putting the crank pulley back or it won't sit flush and will give you fits [emoji106]


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Update: my rattle was indeed the water pump. Axial play (= rattle) in the pump bearing. On order.

Everything else was good - idler, tensioner, alternator, PS pump, belt, etc.

Also, rather than remove the crank pulley, I just removed the tensioner to get access to the water pump bolt hidden behind the crank pulley. Seemed a lot easier than messing with the A/C belt if I didn't have to.

You lucky dog! I tried that with mine but the bolt was too long to come out, it was captured between the water pump and crank pulley with a handful of turns left forcing me to pull my crank pulley to get it removed...

My solution was to buy and ac belt that was a 1/2" longer than factory and REALLY fight with it to get it installed- which I finally did and thankfully it has been working fine since.


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Oh that is good to hear. Unfortunately I didn't have time to work on the car this weekend, so it's still down. New house projects got in the way.

In my case the bottom bolt when fully released was up against the crank pulley. All I had to do was pry the water pump straight forward a bit, then tilt the top of the water pump forward so that the bottom would clear the pulley. Might be a bit of a challenge to install the new water pump in reverse, but I'll give it a try. I plan to tape the bottom bolt in place prior to positioning the pump.

The AC belt is a pain. I slotted the end of the AC belt tensioner bolt so I could adjust it from above with a big flat-head. It's near impossible from below with the large AdaptiveDrive sway bar.

Made it to the WP. There's definitely some play and a rattle when I shake it. AC belt is loose, that adjustment screw is a huge pain, but at least after 30 min of contortionism, I finally found the right way and get the bit in and on it pretty quickly.

I see no easy way of accessing where I think the drain plug is for the coolant. Think I'll just drain the radiator and call it good...

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