Why does the OEM N54 N55 thermostat cover need replacing?

The factory plastic thermostat housing cover is prone to cracking and developing leaks as it ages, particularly given the heat cycling it experiences directly above the engine. The BMW N54 N55 thermostat cover from MMX replaces it with billet aluminum, which does not become brittle or crack the way the OEM plastic does over time.

Is this thermostat cover the same as the thermostat itself?

No. This BMW N54 N55 thermostat cover is the housing cover that bolts over the thermostat assembly, not the thermostat unit itself. It is a cosmetic and durability upgrade that replaces the failure-prone plastic cover; the thermostat that regulates coolant flow remains a separate component underneath.

Does this BMW N54 N55 thermostat cover also fit S55 engines?

Yes. While the N54 and N55 cover the majority of the fitment range, the cover is also compatible with S55-powered F80 M3 and F82/F83 M4 models, since the S55 shares the same thermostat housing design lineage as the N55.

Will the anodized finish discolor from engine bay heat?

Prolonged exposure to excessive heat can affect the appearance of any anodized aluminum finish, which is an inherent characteristic of the anodizing process rather than a defect specific to this product. Under normal operating temperatures in this location, the finish holds up well, but this is worth noting given the cover's proximity to the engine.

How difficult is installation?

The BMW N54 N55 thermostat cover is a direct, bolt-on replacement for the factory cover with no permanent modification required. Most owners complete the swap using basic hand tools in a short amount of time.

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Description

MMX Billet Oil Thermostat Housing Cover Kit for BMW N54, N55, and S55 Engines

BMW N54 N55 thermostat cover from MMX Performance is a precision-machined T6061 billet aluminum replacement for the factory plastic thermostat housing cover, also compatible with S55-powered models. The OEM plastic cover is prone to cracking and leaking as it ages, a well-known weak point that the billet aluminum construction eliminates entirely while adding a clean, motorsport-inspired finish to the engine bay. Each cover is anodized in MMX’s signature gloss black for a refined, consistent look that matches the rest of the MMX billet cap and cover range. Installation is a direct, bolt-on replacement with no permanent modification required, making it a straightforward upgrade during routine maintenance or simply for engine bay presentation.

Features

Precision-machined from solid T6061 billet aluminum
Eliminates the cracking and leaking risk of the OEM plastic cover
Anodized in MMX signature gloss black finish
Direct replacement of the factory plastic thermostat cover
Easy, bolt-on installation with no permanent modifications required

Applications

BMW 135i: E82, E88 | 2007-2013
BMW 1M Coupe: E82 | 2011-2012
BMW 335i: E90, E91, E92, E93, F30, F31, F34 | 2006-2012
BMW 435i: F32, F33, F36 | 2013-2016
BMW 535i: E60, E61, F07, F10, F11 | 2007-2017
BMW 640i: F06, F12, F13 | 2011-2018
BMW 740i: F01, F02 | 2008-2015
BMW M135i: F20, F21 | 2012-2016
BMW M2: F87 | 2016-2018
BMW M2 Competition: F87 | 2018-2021
BMW M235i: F22, F23 | 2014-2016
BMW M3: F80 | 2014-2018
BMW M3 Competition: F80 | 2016-2018
BMW M4: F82, F83 | 2014-2020
BMW M4 Competition: F82, F83 | 2016-2020
BMW X1 xDrive35i: E84 | 2013-2015
BMW X3 xDrive35i: F25 | 2011-2017
BMW X4 M40i: F26 | 2015-2018
BMW X4 xDrive35i: F26 | 2014-2016
BMW X5 sDrive35i: F15 | 2013-2018
BMW X5 xDrive35i: F15 | 2013-2018
BMW X6 sDrive35i: F16 | 2015-2019
BMW X6 xDrive35i: E71, F16 | 2008-2019

Notes

Only compatible on N54, N55, and S55 engines
If these parts are exposed to excessive heat for prolonged periods of time, it can affect the overall finish, which is unavoidable with anodized aluminum products

Frequently Asked Questions

Why does the OEM N54 N55 thermostat cover need replacing? The factory plastic thermostat housing cover is prone to cracking and developing leaks as it ages, particularly given the heat cycling it experiences directly above the engine. The BMW N54 N55 thermostat cover from MMX replaces it with billet aluminum, which does not become brittle or crack the way the OEM plastic does over time.
Is this thermostat cover the same as the thermostat itself? No. This BMW N54 N55 thermostat cover is the housing cover that bolts over the thermostat assembly, not the thermostat unit itself. It is a cosmetic and durability upgrade that replaces the failure-prone plastic cover; the thermostat that regulates coolant flow remains a separate component underneath.
Does this BMW N54 N55 thermostat cover also fit S55 engines? Yes. While the N54 and N55 cover the majority of the fitment range, the cover is also compatible with S55-powered F80 M3 and F82/F83 M4 models, since the S55 shares the same thermostat housing design lineage as the N55.
Will the anodized finish discolor from engine bay heat? Prolonged exposure to excessive heat can affect the appearance of any anodized aluminum finish, which is an inherent characteristic of the anodizing process rather than a defect specific to this product. Under normal operating temperatures in this location, the finish holds up well, but this is worth noting given the cover’s proximity to the engine.
How difficult is installation? The BMW N54 N55 thermostat cover is a direct, bolt-on replacement for the factory cover with no permanent modification required. Most owners complete the swap using basic hand tools in a short amount of time.

About MMX Performance

MMX Performance is a UK-based specialist in performance parts for BMW and MINI vehicles, crafting high-quality upgrades that blend precision engineering, rigorous testing, and motorsport heritage. Driven by enthusiast culture, MMX designs its products in the UK and puts them through track validation to ensure durability, fitment accuracy, and on-road performance. Their catalog spans drivetrain components, spacers, hardware, and chassis enhancements, all tailored to elevate both the driving experience and visual appeal of BMW and MINI models.

Additional Information

The Bulletproof Automotive website contains many thousands of products purchased in multiple different currencies. All of the prices are entered manually and accurately at the time of entry. Due to the consistently fluctuating international exchange rates, at times prices may not be able to be honored at their original intended rate. We apologize for any inconvenience this may cause, unfortunately our website is unable to compensate dynamically for what can at times be volatile changes in the cost of items due to currency values fluctuating, changes in prices from suppliers, changes in shipping and import duties, and other factors. Rest assured that any order you place on line will be at zero risk to you in this area. If in the event your order cannot be fulfilled at the original intended website price we will offer you a 100% refund, no questions asked. We will continue to do our best to maintain updated prices and we will always continue to offer our price match guarantees as well to ensure our prices are always the best for you. In short, prices may change without notice. It is always advised to give us a call prior to placing your order online to confirm availability and to confirm current pricing.

Shipping Policy

Items that are in stock in the US, either at Bulletproof’s warehouse or at a supplier’s warehouse, are generally delivered within 7-10 days. Special order items from overseas take considerably longer. As a courtesy Bulletproof offers delivery estimates to our customers which take into consideration manufacturer availability and shipping schedule. These estimates represent our best guess based on previous orders from the manufacturer and do not in any way imply a guaranteed delivery window. Many manufacturers work in a “just in time” inventory system and often take 2-20+ weeks to produce an item once an order is submitted. All deliverable items are then sent to our Japanese warehouse. Bulletproof ships a minimum of one full ocean freight container every month from Japan, oftentimes more than one a month. Ocean freight takes an average of 4 weeks. Typically it breaks down to one week in Japan for paperwork and customs, two weeks by boat and one week in US customs/clearance. Due to the wide number of variables between manufacturer and shipping schedules, delivery estimates are simply just that – estimates. We attempt to estimate conservatively and we usually deliver faster than our estimates suggest. It is not Bulletproof’s policy to guarantee delivery time of any special order item, this is impossible for us to do. By ordering you acknowledge that there is no required delivery ETA and an order may not be canceled or altered due to manufacturing or shipping delays, all ETA’s are provided as a best guess only. Please review the full Terms & Conditions here.

BP Pricing Difference

We do pricing a little differently on our JDM brands and we believe in making things simple and clear. No hidden fees or surcharges. Every price you see includes the shipping cost to our office in Los Angeles, California and all the associated taxes/duties/fees for bringing the products into the US. The only shipping you ever pay is from our facility in the US to your location. Be wary of resellers that don’t include the cost of international shipping in their pricing on JDM parts. While we believe we’ll always have the lowest all-in price on JDM products, we offer a price match guarantee for all authentic parts purchased from authorized dealers as well. For many international customers, it’s much more affordable to ship from the USA than from Japan directly, as the air freight and ocean freight costs are typically much less. However, for customers looking to ship directly from Japan outside of North America, or domestically in Japan, we can provide pricing specifically for that scenario. Please do not hesitate to contact us with any pricing questions or concerns. Please email us at sales@bulletproofautomotive.com with any inquiries.

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MMX Billet Oil Thermostat Housing Cover Kit for BMW Vehicles (with N54 / N55 / S55 engines) [MMR03-0502-BL]

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MMX Billet Oil Thermostat Housing Cover Kit for BMW N54, N55, and S55 Engines

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Frequently Asked Questions

About MMX Performance

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