BMW X4 M40i Serpentine Belt
Factory serpentine belt specifications for the BMW X4 M40i.
Last updated: 2026-11-01 • Reading time: 8 min • By AllOEMManuals Editorial Team
Quick Answer
2019-2024 BMW X4 M40i: REPLACING DRIVE BELT FOR ALTERNATOR (X4 xDrive30i 2019-2021) REPLACING DRIVE BELT FOR ALTERNATOR (X4 xDrive30i 2022-) REPLACING DRIVE BELT FOR ALTERNATOR (X4 M40i 2019-2021) REPLACING DRIVE BELT FOR ALTERNATOR (X4 M40i 2022-).
| Generation | Years | Top spec |
|---|---|---|
| 2019-2024 | 2019-2024 | REPLACING DRIVE BELT FOR ALTERNATOR (X4 xDrive30i 2019-2021) REPLACING DRIVE BELT FOR ALTERNATOR (X4 xDrive30i 2022-) REPLACING DRIVE BELT FOR ALTERNATOR (X4 M40i 2019-2021) REPLACING DRIVE BELT FOR ALTERNATOR (X4 M40i 2022-) |
| 2016-2018 | 2016-2018 | N20 engine: REPLACING DRIVE BELT FOR ALTERNATOR N55 engine: REPLACING DRIVE BELT FOR ALTERNATOR |
This vehicle's factory manual
BMW X4 M40i: choose your year, then confirm the engine, trim, or drivetrain to open the available repair and diagnosis sections.
BMW X4 M40i maintenance schedule
Know the exact serpentine belt job for your BMW X4 M40i
2019-2024 BMW X4 M40i: REPLACING DRIVE BELT FOR ALTERNATOR (X4 xDrive30i 2019-2021) REPLACING DRIVE BELT FOR ALTERNATOR (X4 xDrive30i 2022-) REPLACING DRIVE BELT FOR ALTERNATOR (X4 M40i 2019-2021) REPLACING DRIVE BELT FOR ALTERNATOR (X4 M40i 2022-).
Belt routing and length change with engine code, accessory package, and tensioner layout. Do not order parts off a generic diagram. Once the spec is confirmed, use the supplies and purchase links below to build the full one-trip shopping list before you start the repair.
Exact Vehicle Check
The button opens the factory book for this vehicle. Use the engine picker only when your trim is not the one this page already matched.
2019-2024
2016-2018
Parts and supplies
These links search for related products. Check your year, engine, specification, and fitment with the seller before ordering.
BMW X4 M40i Serpentine Belt
Confirm the specification and fitment for your exact vehicle before ordering.
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Serpentine Belt — Manual's Parts List
Belt, tensioner, and the tool to do it right.
- 1Serpentine BeltShop →
Exact length and rib count for your engine
- 2Belt TensionerShop →
Inspect and replace if the service procedure calls for it
- 3Idler PulleyShop →
If it wobbles or squeaks, replace it while you are in there
- 4Breaker Bar (1/2")Shop →
Use the tool specified in the service procedure
- 5Belt Routing DiagramShop →
Take a photo before you remove the old belt
Get everything at once
Search results vary; confirm each item and its fitment before buying.
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One-Trip Shopping List
Recommended supplies and tools for this job, grouped so you can buy everything before the repair starts.
Exact Serpentine Belt
Match engine-specific length and rib count for the cleanest fit.
Belt Tensioner
Replace weak spring-loaded tensioners that cause squeal and slip.
Idler Pulley
Quiet bearing support when the belt is off anyway.
Pulley Puller Set
Useful for stubborn idler and tensioner pulley swaps.
Breaker Bar
Makes tensioner release easier in tight engine bays.
Shop Towels
Keep the accessory drive and your hands clean during inspection.
Project Essentials
Basic tool sets, gloves, and cleaning supplies for your BMW X4 M40i so the job is ready when the parts arrive.
Frequently Asked Questions
- What serpentine belt does a BMW X4 M40i use?
- 2019-2024 BMW X4 M40i: REPLACING DRIVE BELT FOR ALTERNATOR (X4 xDrive30i 2019-2021) REPLACING DRIVE BELT FOR ALTERNATOR (X4 xDrive30i 2022-) REPLACING DRIVE BELT FOR ALTERNATOR (X4 M40i 2019-2021) REPLACING DRIVE BELT FOR ALTERNATOR (X4 M40i 2022-).
- How do I know if my BMW X4 M40i serpentine belt is bad?
- Common signs include squealing on startup (especially when cold), visible cracks or fraying on the ribbed side, power steering or A/C failure, and battery warning lights. The factory manual includes inspection criteria and replacement intervals.
Find your service manual
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Author & Review
Published by AllOEMManuals, founded by Lyndon Bedford, an automotive technician with 20 years of experience. He owned and operated a mechanic shop in Hurst, Texas from 2014 to 2022 and continues hands-on repair work.
Content may combine manual references, general repair templates, and AI-assisted drafting. Confirm the source, vehicle configuration, and applicability before working. Report corrections through our contact page.
Last updated: 2026-11-01