Home Repair and Service Manual Auxiliary Coolant Pump Replacement – BMW B46/B48 Turbo 4 Cyl. Engine

Auxiliary Coolant Pump Replacement – BMW B46/B48 Turbo 4 Cyl. Engine

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Auxiliary Coolant Pump Replacement – BMW B46/B48 Turbo 4 Cyl. Engine

There can be several different auxiliary coolant pumps in BMW engines, but this article deals specifically with the one that cools the turbocharger unit in B46/B48 4-cylinder engines. The turbocharger in your BMW is subjected to brutal heat conditions - the temperature of exhaust gases leaving the unit can be in excess of 1000 degrees F. If not cooled properly, the turbocharger will fail. The auxiliary turbocharger coolant pump helps keep the temperature within acceptable operating limits and should be replaced immediately upon any signs of malfunction. This article gives detailed step-by-step instructions on replacing the auxiliary turbocharger coolant pump in BMW B46/B46 engines.
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Possible Symptoms: Turbocharger overheating, severe decrease in performance, turbocharger failure
This repair can be used on the following BMW models:
Intermediate level repair.

Step 1 - Purchase Parts

You will need the following parts and supplies to perform this repair.

Auxiliary Coolant Pump

The turbochargers in your BMW get hot...we mean seriously hot. These brutal conditions take their toll on the turbochargers internal parts, especially the bearing seats. Without proper cooling, the turbochargers lifecycle is seriously shortened meaning an expensive trip to the repair shop. This Genuine BMW auxiliary turbocharger cooling pump is the same factory pump installed at the dealership. Don't be fooled by cheap aftermarket pumps sold on Amazon and Ebay...they do not last and can end up damaging your engine.

Step 2 - Repair Procedure

Unless otherwise noted, all vehicle repair step images in this article are copyrighted, and used courtesy of BMW of North America, Inc. .
The high temperature coolant system must be drained before starting this repair.

For detailed instructions on how to drain and refill the high temperature coolant system, please see our article Coolant Flush and Replacement - BMW B46/B48 Turbo 4 Cylinder Engine.

1. Replacing the turbocharger auxiliary coolant pump
Remove the acoustic cover from the engine
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- Remove the acoustic engine cover by pulling it up until it releases from its rubber grommets.

View part diagram for this step
remove the radiator cover
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- Remove the radiator cover (1) by pulling it up until it releases from its rubber grommets.

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remove the intake muffler
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- Disconnect the hot-film air mass meter (1) from the intake muffler (4).

- Loosen the hose clamp (2) connecting the intake silencer to the clean air pipe (3)

- Grasp the intake muffler and pull it loose from its rubber grommets and remove from vehicle.

View part diagram for this step
remove the clean air pipe
Click to enlarge image

- Next, remove the clean air pipe (4) by first disconnecting the vent pipes (1) and (2).

- Unlock the spring clip (3) and pull the clean air pipe free from the turbocharger.

View part diagram for this step
remove the charge air line
Click to enlarge image

- Unplug the charge air pressure sensor (1) and the temperature sensor (3).

- Remove the three torx screws anchoring the charge air line to the throttle body.

- Release the locking clamp (4) and pull the charge air line free from the turbocharger.

- Remove the charge air line from the engine compartment.

View part diagram for this step
cut the front acoustical panel where it is perforated
Click to enlarge image

- Locate the front acoustical cover mounted to the lower front of the engine.

- Using a razor knife, cut the small tabs shown in the image.

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remove the plastic rivets anchoring the front acoustical cover
Click to enlarge image

- Remove the plastic rivets anchoring the acoustic cover to the engine. Remove the cover from the engine compartment.

View part diagram for this step
disconnect the coolant lines from the auxiliary coolant pump and unplug
Click to enlarge image

- Locate the auxiliary coolant pump on the front of the engine.

- Disconnect the coolant hoses and unplug the electrical connector (2).

View part diagram for this step
remove the two torx bolts anchoring the auxiliary coolant pump to engine
Click to enlarge image

- Remove the two torx bolts (1) anchoring the auxiliary coolant pump to the engine block. Remove the coolant pump from the engine.

View part diagram for this step
2. Final installation notes and torque values

- Torque coolant pump to engine block mounting bolts to 8 Nm (6 ft-lb).

- Make sure when reinstalling the coolant lines you hear them firmly snap into place.

- Follow the instructions in our article Coolant Flush and Replacement - BMW B46/B48 Turbo 4 Cylinder Engine on refilling and bleeding the coolant system.

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