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BMW Engine Coolant Outlet Hose Fitting may FAIL,

BMW engine coolant outlet fitting (BMW Part: 11537541992) may break or crack while the engine is running causing coolant loss (and engine overheating if ignored).

If you notice coolant leak from the thermostat to cylinder head coolant hose this is often the culprit.

The original outlet is made of plastic and is prone to failure. The part is found on many BMW models including the popular BMW 335i.

This part is found on N54, N53, N52 and N51 3.0-litre motors.

bmw coolant hose leak

The best solution is to replace the plastic fitting with a metal part that will not leak and crack like the original.

Continue reading to learn how to replace BMW water hose fitting yourself with the upgraded part.

This is a recommended upgrade if you race your BMW or live in a city that frequently sees high temperatures. 

TIP! Note that BMW dealer may recommend that the thermostat hose needs to be replaced in order to fix this problem.
When purchased from the dealer the broken part may come as one part with the hose. We could not verify if BMW sells only the outlet fitting.  This problem can be fixed by replacing the defective fitting and it is not necessary to replace the coolant. The hose should be replaced if it is leaking or damaged. 

What you will need

  • BMW PN 11537541992 or 11537544638
    • Interchangeable parts. 
    • Fit the N54, N53, N52 and N51 3.0-litre motors

We would recommend that you replace this part with the new aluminum design so that it will not fail like the original fitting did.

The other advantage of the aluminum design over the OEM part is that the aluminum fitting has a larger diameter which improves the coolant flow. 


The fitting is mounted with two bolts and has a 1-inch diameter.

The hose connects the coolant thermostat housing hose at the front of the engine. 

  1. Park your BMW and allow the engine to cool down. Set the parking brakes. 
  2. Pull the hood release under the dashboard on the driver's side. 
  3. Open the hood and locate the coolant fitting near the front to the engine. bmw cracked coolant hose outlet


  4. Remove two 10mm bolts. BMW 335i 11537541992 11537544638 OEM WATER HOSE FITTING REPLACEMENT ALUMINUM6061


  5. Remove the old fitting from the engine block.BMW 335i 11537541992 11537544638 OEM WATER HOSE FITTING REPLACEMENT ALUMINUM6061The O ring needs to be removed as well as it may get stuck inside. 1pc Water Hose Fitting BMW 335i Aluminum6061 OEM# 11537541992 11537544638


  6. Clean the outlet on the engine block. Remove any remaining pieces from the coolant hose. BMW N54 335i 335xi Water Hose Fitting Replacement


  7. Install the new fitting. Lubricate the seal O ring before installation. Tighten the two 10 mm bolts. OEM 11537541992 11537544638 BMW N54 Water Hose Fitting Replacement Aluminum6061


  8. Slide the coolant hose on the outlet port.bmw coolant leak


  9. Tighten the clamp. bmw coolant leak hose


  10. Add engine coolant. It is recommended to only use BMW engine coolant


This guide applies to the following vehicles: 

  • N54 3.0L twin-turbo motors in 335i, 335xi, 135i 
  • N53 (3.0-litre non-turbo) in 2006 - 2010 325i, 330i, 525i, 525xi, 528i, 528xi, 530i, 530xi 
  • N20 (2.0-litre turbo) Z4 2013 and newer
  • N52 X3
  • N55 motors 


Cesar, 2019-03-16

The metal piece of mine is semi broken. I am concerned if that piece may have fallen down through the tube into who knows what? Any advice ?

Visitor, 2019-03-21

On what part of the coolant outlet? Is this the original manufactures' outlet? If so, most original ones are made with a composite plastic resin with two small metal eyelets where the 10mm bolts go to mount the fitting, so it tends to brake down into an almost wood like substance when exposed to extremely high temps over time. In this situation I don't believe the engine or transmission would be a major concern if a piece broke off, other than the possibility of a coolant leak and overheating. But if your fitting does happen to be metal then I would say an immediate flush of the system would need to be performed. Hope this offers any useful information to you. Best of luck and Happy Trails!

Visitor, 2019-03-24

Do you have to drain your coolant before changing this fitting

Jared, 2019-05-15

No you don't have to-- I just did mine during my lunch break. the hose will have coolant so I put a paper coffee cup underneath and emptied enough out of the hose to put it in place again. top up coolant and bleed w/ water pump procedure after.

Eddy, 2019-05-28

Where can I buy this fitting and hose assembly because for my 328i this area was the source of the leak. I opened this hose and the fitting was damaged. So it needs to be replaced.


Kosta, 2019-06-29

Did anyone had white vapor come from the radiator at first.?
Cuz the coolant was sprayed there?

Dina, 2019-07-15

Where can you purchase the medal connector from? No auto stores I’ve been to don’t seem to have it 😢

By YOUCANIC on May 12, 2019


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