BMW N54 335i Billet Water Hose Fitting | MTC Motorsport | OEM Replacement 11537541992 11537544638
Upgrade your BMW coolant system with the MTC Motorsport billet aluminium water hose fitting, a precision CNC-machined direct replacement for BMW part numbers 11537541992 and 11537544638. This high-strength 6061 alloy fitting replaces the fragile plastic connector on the thermostat housing side, helping to prevent the cracks, leaks and breakdowns that are common with the factory plastic part on N54, N53 and N52 engines.
Perfect for BMW N54 335i and 135i owners looking for a reliable, permanent solution, this billet water hose fitting delivers improved durability, leak resistance and long-term peace of mind while retaining a factory fit with no modifications. Designed to accept the standard 25 mm hose.
Key features
- Direct OEM replacement for 11537541992 and 11537544638
- CNC machined from billet 6061 aluminium for strength and longevity
- Replaces the known weak plastic thermostat housing fitting that commonly cracks and leaks
- Factory-style fitment with the standard 25 mm coolant hose
- No modification required to the coolant system
- Engineered to resist wear, cracking and heat cycling
- Supplied in bare aluminium finish
Engine and model compatibility
Fits the following BMW petrol engines and models as per the original part application:
- N54 3.0L twin-turbo: 335i, 335xi, 135i
- N53 3.0L non-turbo 2006 to 2010: 325i, 330i, 525i, 525xi, 528i, 528xi, 530i, 530xi
- N52: X3
- N20 2.0L turbo: Z4 2013
- Also fits N55 engines when using a slightly thinner O-ring
Why upgrade this fitting
The stock plastic connector between the coolant thermostat housing and the front of the cylinder head is a well-known failure point that can crack and leak with age and heat cycles. Swapping to this MTC Motorsport billet aluminium fitting provides a robust, long-term solution that maintains OEM hose routing and connection while dramatically improving reliability.
Installation
Installation is straightforward: remove the hose from the original plastic fitting, remove the plastic fitting from the head, install the billet aluminium fitting in its place, then slide the hose and clamp back on. Ensure you use an appropriate O-ring for your engine variant, especially on N55 which requires a slightly thinner O-ring.
Prefer professional fitting? Nforcd in Warwickshire can help. Request a fitting quote at Sales@nforcd.com.
What we think
We have used this MTC Motorsport billet water hose fitting on our own cars and customer vehicles and the results have been excellent. Customers consistently report a perfect fit, no leaks and the confidence that comes with eliminating a common plastic weak point.
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