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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 02-05-2016, 02:19 PM   #1
NLM Hollywood
Registered User
Join Date: Oct 2014
Location: MN
Posts: 9
My Ride: 2001 330xi
A proper write up on tensioner and pulley replacement

Did a search on tensioner, idler and pulley replacement (including torque specs) and the info available was weak to say the least. Figured since it was fresh (did it yesterday) I'd do a proper thread.

Tools used
3/8 drive breaker bar (Snap On FHBB12)
3/8 drive flex head ratchet (SO FHF80)
3/8 drive torque wrench (SO TECH2R100)
16mm 6 point (SO FSM161)
13mm 6 point (SO FSM131)
10 mm 6 point (SO FSM101)
3/8 drive 3" knurled extension (SO FXK3). A wobble or universal (SO FU8A) could be helpful in reaching the upper 13mm bolt on the lower AC tensioner.
3/8 drive T50 Torx (SO FTXB50E, but recommend trying the stubby FTX50SE for added safety)
3/8 drive 8mm Allen (SO FAM8E, but recommend trying the stubby FAMXS8E for added safety)
1/4 hex shank bit T25 Torx bit (SDMT25D. Also part of SO SDM400A bit kit)
Pliers (SO95BCP)
Small flat blade screwdriver or pick (I used SO SDD2040)

My 01 330xi is a manual (wouldn't own it otherwise), so I have an electric puller fan that's easy to get out without the need for the 32mm fan clutch tools.

I started by removing the 3x plastic rivets holding the air intake manifold down using pliers. Then wiggle the manifold apart from the intake tube and remove both. Then remove the 2x 10mm bolts securing the airbox. Also disconnect the hose clamp securing the airbox to the rubber boot and disconnect the wire assembly connected to the MAF. Once this is all removed I started on the fan.

My car has 1x plastic rivet and 1x T25 Torx bolt securing it. Remove both, disconnect the two fan wire assemblies on the left hand side and pull the fan up and out. With the airbox and fan out of the way there's plenty of room. I've seen a few vids where the upper rad hose was disconnected from the T stat housing and I found this completely unnecessary.

Start by removing both belts (AC belt removal not necessary unless you plan to replace the AC tensioner or replace the main accessory belt). First remove the plastic covers over the main accessory tensioner and idler pulley. As I replaced both tensioners and the idler pulley, I started with the AC belt. My AC tensioner required a T50 Torx to detension. Once the belts off I moved on to the main belt. Here's where I found the first bit of incorrect info about this. In a couple places I read this was also a T50 Torx bit, so that's what I used to detension and it worked fine. Only after removing the hydraulic tensioner and looking at the pulley did I see the correct tool is an 8mm Allen and NOT a T50 Torx. The T50 Torx bit fits inside and works, but damages the threads in the process. Since this tension/detension action takes a decent amount of force, I highly recommend using the correct tool unless you look forward to stripping the bolt.

Once the main belt is released I removed the idler pulley using a 16mm socket. Pay attention to the backside washer and its orientation. Next remove the 3x 13mm bolts securing the hydraulic tensioner to the block. The 3" extension comes in handy here and the knurled version makes using your hand to spin them out easy. Keep track of which bolt comes out of which hole if you plan to reuse them as I did. ROEM could be helpful if you bought new ones or loose track.

Next I removed the 2x 13mm bolts securing the mechanical AC tensioner. The upper bolt was a tad off axis and a wobble or universal could be helpful. I was able to get it off fairly easy without. The lower bolt was much was easier to get at from underneath the car (I hate plastic undertrays and leave them off, making this possible).

Next I installed the new main hydraulic tensioner and torqued all 3x bolts to 24Nm. The lower left both is nearly impossible to see, so you need to guess. The pics I've included should help with the guesswork. Then I installed the new pulley (tensioner needs to be mounted to the car first) and torqued to aprox 45Nm (30Ft/Lbs). This was also pretty close to the full detension position of the pulley, so a torque wrench isn't really necessary.

Then I installed the new idler pulley, making sure to reuse the original washer on the back in the correct position. Torque was 45Nm or 33Ft/Lbs.

Lastly the new AC tensioner went on. The original part had the pulley as a separate item secured with a bolt. The new part was one piece, with the pulley a permanent part of the assembly.

With all 3 new items installed, I put both belts back on, detensioning the main hydrualic tensioner with the 8mm Allen and T50 Torx for the AC mechanical tensioner (try the stubbys if you have them) . Make sure both belts are fully seated on all pulleys.

After double checking, reinstall the fan, airbox and plastic air inlet manifold. Don't forget to tighten the hose clamp securing the airbox to the rubber boot and reconnect the MAF wire. Double check belt routing before starting.

Give it a test and check with a flashlight to make sure everything is moving freely.
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Last edited by NLM Hollywood; 02-09-2016 at 03:07 PM.
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Old 02-08-2016, 10:39 AM   #2
John in VA
Registered User
Join Date: Oct 2007
Location: Leesburg, VA
Posts: 742
My Ride: 328i/325xi/328iX
Nice work! The large block of text makes my eyes water, but it's easy enough to copy/paste & edit. Could you supply a new parts list/part numbers?
John in VA
'13 328iX
'03 530i
'02 325xi
'00 328i
'86 535i
'85 535i
'85 325e - RIP
'74 2002tii

Last edited by John in VA; 02-08-2016 at 10:39 AM.
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Old 02-09-2016, 03:18 PM   #3
NLM Hollywood
Registered User
Join Date: Oct 2014
Location: MN
Posts: 9
My Ride: 2001 330xi
Part #'s

I used INA replacement parts purchased from Bav Auto. These are the Bav Auto part #'s. Original BMW part #'s included below.

Part #: Item: Price:
532 0001 100 BELT TENSIONER PULLEY - INA $14.95
534 0104 100 TENSIONER FOR AC BELT - INA $49.95



21 Complete hydraulic belt tensioner 11287838797 $69.64
06 ADJUSTING PULLEY 11281748131 $45.97
15 Deflection pulley 11287841228 $46.81
02 ADJUSTING PULLEY 11281433571 $114.67
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Old 02-10-2016, 08:33 AM   #4
Zero. Leaks.
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Join Date: May 2008
Location: NYC
Posts: 29,536
My Ride: '02 330i 6MT
Thanks for the write up.

Moved from the xi section to the diy section.
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Old 02-11-2016, 08:16 AM   #5
Registered User
Join Date: Jul 2008
Location: USA
Posts: 4,619
My Ride: 2001 330Ci
I replaced the tensioner pulley yesterday. The belt was impossible to get back on until I used this trick:
- loosen the idler pulley bolt until the idler pulley bolt can rotate
- put the belt around the pulleys ensuring proper routing
- using a ratchet and torx in the tensioner pulley bolt compress the tensioner
- make sure the belt is fully aligned with all pulleys
- release the tensioner
- rest (hey, I'm an old guy!)
- have someone (strong) recompress the tensioner
- rotate the idler pulley bolt until the locator "bar" on its rear aligns with the slot
- tighten the idler pulley bolt.
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