XSeries-forum

Hi all - grateful as ever for some thoughts on the following:

My car is an E53, N62 4.8. The main auxiliary/serpentine belt was squeaking when I bought the car, so I replaced the idler pulley and (sort of) the tensioner as well (I say sort of, because I didn't notice the locking pin in the new tensioner, installed by BMW at the factory, and shattered the housing when I tried to de-tension it! (yes - I am a dck...) So I swapped over the new pulley from the new tensioner onto the old tensioner....). I also swapped the AC belt and serpentine belt.

This was fine for a few thousand miles, but then started to squeal on start up - and now, there is a rattle. It goes away when the car has warmed up - and I'm pretty sure it's not a vanos-type noise or other form of engine knock - but I think it sounds like bearing rumble... I haven't been able to remove the belts to check as I don't have the correct socket at my London address (all my major tools are at my folk's place....) - but wondered on the likelihood of it being water pump or alternator bearings - and how to test for sure? Would a water pump make a rumble - or simply leak...?

I have to replace the thermostat as it's stuck open - so was going to do the Bimmerfix coolant pipe install as preventative maintenance while I was in there, and was considering changing the water pump as well - as the car now has 105,000 on.

Any thoughts on the rumbling noise, and how best to check whether it's the water pump or alternator? The other option is potentially to also replace the tensioner (again, but a bit more carefully this time...) - as I have installed a new pulley on the worn arm of the old tensioner - so in theory that could have prematurely damaged the pulley on the tensioner?

Many thanks!

If you are thinking of changing the pump then i would do that well worth doing while you are in there as said.
Also i would change the pulley then after all is done your only left with the alternator.
First tho i would run it up with the belt off and i bet you have no noise.

That’s a good idea actually (running without the belt....) - will give that a go - and think it’s probably a good idea to change the water pump at this mileage.

I recently had a similar issue started with vibration when accelerating around 3000 rpm then a squeal on startup that went after it warmed still the vibration though. My thoughts were AC pump or Water pump/Alternator for the vibration. Squeal rapidly worsened so decided time to fix it.
I ordered both tension units and both belts and stripped out the bits in the way (engine fan cowl and under trays) Both belts were showing signs of wear when removed so in the bin they went both tension units looked OK but as I had new I was going to replace them. I started the engine with no belts, quiet and smooth stopped the engine and checked the water pump pulley free and smooth no sign of leaks alternator the same as was the AC pump started the engine again and noticed the crankshaft pulley seemed to have a slight wobble.

I have read about the rubber insert in the crank pulley breaking down so got under the car to get a better look. What I found was I could move the crank pulley by hand !!! Got a suitable socket and found I could undo the Jesus bolt by hand (gulp) took out the bolt and removed the pulley, the pulley being loose had allowed it to rotate shearing the woodruff key in the crankshaft and wearing the pulley boss that was the vibration and squeal.
I had to order a new crankshaft boss and key from BMW all back together and new Jesus bolt torqued correctly and I have a smooth running car again.

So check the crankshaft pulley and Jesus bolt while your in there

Many thanks for this - had half wondered about it actually as there may be a slight wobble.... so to check - remove fan shroud (for access) - and belts - and then check for play in the crank pulley? If I remove the pulley, I assume there’s no seal which will fall out/engine oil will come pouring out?(!).

How did you re-torque the crank pulley nut without turning the engine over - impact gun?

Thanks again!

Sounds like somebody had re-used the " Jesus bolt " without putting any lock-tight/thread-lock on it.
They say to use new but over the years i have re-used them with no problems.

...so just to check - do  you mean the vibration dampener (which I think is the main drive pulley off of the crank)?:

http://www.realoem.com/bmw/enUS/showpar ... Id=11_3260

That's the one.
They do fail in time the one on my sisters 320d fell off but she does neglect her car's.

Thanks for this - I’ll take a look - assume should be obvious if it’s loose!

It's bonded together with rubber i think.
Get a camera down/up there for a closeup look.

Morning
My engine was rebuilt 30k ago I can only assume that the bolt wasn't torqued correctly (or at all) at that time.
The main crank pulley/vibration damper and pulley boss are separate parts, my crank pulley was fine it was the boss which had become damaged. It should be a tight slide fit, mine was really worn and loose from rotating (the squeal) fortunately the crankshaft was not damaged so after removing the damaged woodruff key the key was replaced and the new boss fitted. I made up a tool to hold the boss and set about tightening it up, it's tightened first to 100 ft/lbs then using a degree gauge in 3 stages 60deg 60deg then 30, final toque is somewhere around 350 ft/lbs and yes I used  threadloc.

I would rate the job as simple to carry out just take your time, hopefully yours isn't as extreme as mine. Mine was the result of sloppy workmanship (someone not finishing a task before moving to the next) then not checking. Good luck I hope yours is a simple fix.

Thanks for this. Will investigate at the weekend as will head to my folks where I can remove the fan shroud and belts. The main serpentine belt seems to travel/oscillate about 3mm or so on the water pump pulley - but I can’t detect any wobble/ movement of the pulleys themselves by eye.

Assume it should be obvious with belts off when I turn the main crank pulley bolt with a ratchet. If it’s tight then assume it’s OK?! So no need to remove it to check parts (ie it’ll be obvious if there’s play/slop?).

Much appreciated re the detailed replies above - I suspect it’s alternator bearing or water pump - hopefully the water pump, as I’d planned to replace that already.

Thanks again all.

If you can undo the main crank bolt with a normal ratchet then you have the same issue I did. I needed a 6ft bit of scaffold pipe to tighten it correctly so if you can undo it with a standard ratchet ???
If it is loose then take it off and check the woodruff key it only locates in the first 5mm of the boss key way under normal circumstances this would be enough to locate the boss correctly then the Jesus bolt add's a massive clamping force. When your belts are off if you turn each ancillary pulley by hand you will soon feel the worn one it will feel rough/notchy.
As the jesus bolt was not tight on mine I can see that when the load comes on Alternator, water pump, power steering pump and AC pump gradually it twisted and then sheared the woodruff key the boss was then free to turn on the crankshaft. Result squeal, vibration and rapid belt wear.

Sounds as though your weekend activities are taken care of good luck fingers crossed all goes to plan.

Yep. Gunna be busy! Thanks again for the detailed info. Really helpful.