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-   -   Serpentine belt - am I crazy? (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/113469-serpentine-belt-am-i-crazy.html)

Russianblue 07-14-2021 12:19 PM

Serpentine belt - am I crazy?
 
When i cranked the 2003 M54 for the first time after the head gasket change, i was greeted with a screeching noise of epic proportions. I thought it was coolant or something on the brand new serp belt and figured it would go away.

It DOES go away after the car warms up. But if it cools down for a minute, it's back. and it's entirely too loud for the neighborhood. Anyway, i took off the serp belt and cranked it this morning and ran the car for 20 seconds. No screech.

Conclusion, it's either the water pump, the alternator or the PS pump.

Strangely, all three pulleys spun like new. I was expecting to feel some shaft play at least. But this thread is not about that problem yet.

It's about this: I went to put the belt back on and it will NOT go on. Spent 2 hours trying different techniques. For most of the effort, I even went back to the OLD serp belt because it's stretched nearly an inch longer.

I have no idea what to think. I MUST be missing something simple.

Good question. Glad you asked. Here is how i have it routed. I would LOVE for this to be a routing issue.


Routing:
https://i.postimg.cc/c1pWZdrH/2021-07-14-11-55-22.png

and HERE is my install technique.

https://youtu.be/V2DcOH068wE


the only way that loop is getting around that tensioner is if i PRY something in there and i don't even think THAT will work. I honestly think i need another full INCH or two of slack.

I have unbolted and reseated the idler pulley and checked to make sure everything is lined up properly.

I remember this being a little difficult to install initially. nothing like the videos online where they just slip it over the tensioner. i had the radiator out and had room to shove it onto the pulley with the heel of my hand. then i started thinking...is it possible that the tensioner being SO tight (at the end of it's range) contributed to the screeching noise? several problems going on here. feel free to address them as you will. What am I missing?

crystalworks 07-14-2021 12:46 PM

What's the part number on the belt? Your routing is fine.

Edit: I remember it being possible to install the tensioner in an incorrect orientation. That might be a possibility.

andrewwynn 07-14-2021 01:26 PM

Serpentine belt - am I crazy?
 
How are you removing tension from the tensioner? There should be a 17mm? Hex in the arm but often people use the T50 in the axle of the pulley.

I recalled my new belt being quite snug but also I don't think an old belt will stretch more than about 1/3" so I think you have an incorrect part. Either the wrong part number or labeled wrong at the factory.

The reason I think this is it happened to somebody else on xo within a year. Serp belt was about an inch too short. Brought it back to the store and sure enough the correct part was an inch longer.

oldskewel 07-14-2021 02:49 PM

Your routing looks right, but just in case, here is a video with a clear view:
https://www.youtube.com/watch?v=CV9spXG7xqw

I think your technique is better - the last step is to slip the belt over the tensioner pulley (smooth outer edge) vs. he does it over the PS pulley which is tougher.

The belt I used was Continental Elite / Goodyear 4060604
The number in there indicates the length as 60.4 inches. I also measured my old and new ones with a belt measuring tool, and confirmed that. Old belt was 60.5". I forget details but there is some spec about how to measure to account for the inner surface vs. outer surface (my tool takes care of that for me).

But since your belt is new, I'd try to measure it. Is the old belt already in the landfill?

That idler that is held by one of the alternator bolts has a little boss on the back of it to hold it in a particular orientation. As @AndrewWynn mentions, that is an easy one to miss.

More info, from my notes that I sent you earlier:

Alternator 2x 16mm M10 bolts (one through idler pulley) do not show a torque spec, so I did 40 Nm, guided by the Bentley M10 8.8 max spec of 47 Nm.

Both the drive belt tensioner and the AC belt tensioner have a 16mm hex boss so a 16mm hex socket can be used to loosen them. Both turn clockwise to loosen.

For the Drive Belt tensioner, the belt rides under the idler pulley (at 10 o'clock to the alternator pulley), and to the right of the tensioner pulley (so the belt goes around the water pump pulley, around the tensioner pulley, then around the crankshaft pulley, then PS pump, then alternator, then idler).

X5chemist 07-14-2021 03:50 PM

The starting noise is probably the secondary injection pump. I just replaced mine. Sounded like a jet engine starting up.
https://xoutpost.com/bmw-sav-forums/...urchase-3.html

The hydraulic tensioner can be hard to compress. Use a serpentine belt tool or super long ratchet.

oldskewel 07-14-2021 06:34 PM

https://blog.fcpeuro.com/m52tu-m54-s...elts-explained

^^^ that's actually a nice resource there, clearly showing the belt path, etc.

They used both mechanical (spring) and hydraulic tensioners on these M54 engines. Can be replaced interchangeably.

My 2001 has a mechanical one (and came with one). From @Russianblue's video, it seems to be moving as my mechanical one would. I don't know if they switched over at some model year (2002?), but even if I did, the fact that they can be replaced with either one means it's probably unknown.

And here's the idler pulley.
https://www.fcpeuro.com/products/bmw...ey-11287841228

That little nub sticking out on the back side is supposed to fit in a hole to keep it aligned. That's the thing that is pretty easy to get wrong.

guntherrex 07-15-2021 07:03 AM

no clutch fan on this motor?

Russianblue 07-15-2021 10:41 AM

I am an embarrassment to this forum and all its fine patrons and apologize for wasting your time!!

First off, I have both belts. Old and new. The old one has been on the car three years. I couldn't get either one re-installed yesterday. I HAD gottten one of them on on Monday though. No idea how i did that. anyway, both have the same part number and came from FCP. The old one has stretched about maybe 1/2 inch. Not as much as I previously estimated.

As I often do with something like this, i take everything apart and put it back together. I drained the PS Fluid, coolant, removed the radiator, removed the t-stat, removed the idler and tensioner.

All looked good, until it was revealed to me that when SOMEONE installed the alternator (me), the lower mount (with the interference fit and the bushing) was not bolted to the Oil Filter housing. It was just resting on top with the bolt tightened through the little bushing in the back. :banghead:

in other words, when I loosened the upper alternator bolt a hair, i could swing the alternator up and down.

I am here humbly to admit my mistake and let everyone know that when you are buttoning up a head gasket install, many hours into the day, you should probably slow down your pace with the IPAs, less'n you make a bonehead mistake like that which (if the belt slipped off or broke...still shocked i got it installed at all) could ruin a number of accessories by having too much tension, not to mention kill your water pump etc.

Thanks for all your input and help though. I just have to laugh at how ridiculous this is, but i suppose stuff happens!

andrewwynn 07-15-2021 10:44 AM

Wow that's a fun mistake. I was just telling the story of when I replaced my alternator I broke my thermostat in half. Best part: caught on video with my taking in what the hell just happened with a subtle "fuck me" when I see the coolant splashing on the ground.

crystalworks 07-15-2021 10:59 AM

:thumbup: We've all been there. I also have stories like Andrew mentioned. Thanks for the recount of what happened though. I'm sure you aren't the first, or last, to have done this.


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