BMW FORUM

Diagnosing and Replacing the Water Pump on a BMW E39 535i

In this article, we’ll discuss the diagnosis and replacement of a suspected water pump failure on a BMW E39 535i. Our initial inspection revealed signs of coolant leakage and abnormal behaviour from the water pump, leading us to take a closer look.

Identifying the Problem

Upon examining the engine, we observed coolant splashed around and noted that the water pump pulley was wobbling significantly. This is an indication that something is amiss, as the pulley should not exhibit such movement. Additionally, a squeaking noise was present, further pointing to the water pump as the likely culprit.

We noticed the cooling fan was also covered in coolant, and there were warning lights indicating low coolant levels and elevated engine temperature. While it was challenging to pinpoint the exact source of the leak due to the coolant splashing, we could see evidence of leakage at the water pump.

Preliminary Steps

To proceed with the repair, the first task was to drain the coolant from the radiator. For this, we needed to remove the fan shroud. The shroud was primarily secured by two rivets, which we carefully popped out. Once these were removed, we had to disconnect a hose linked to the expansion tank to fully free the shroud.

While we searched for the radiator drain, we encountered some coolant spillage. Unfortunately, the drain was elusive in this particular model. However, we continued dismantling components to access the water pump.

Removing the Fan and Accessing the Water Pump

We faced difficulties removing the fan, primarily due to limited access to the bolts. After some deliberation, we opted to leave the fan in place temporarily and try accessing the water pump bolts directly.

Once we managed to remove several pipes and accessories, we took a moment to document the belt layout before proceeding to take the belt off. This is crucial for reassembly later.

When it came to removing the water pump, we found it challenging due to the positioning of certain bolts. Ideally, removing the tensioner would provide better access, but we lacked the right tools at that moment. Eventually, we managed to extract the water pump, although we noted that two pipes connected to it had popped out during the removal process.

Concerns About Pipe Connections

The popped pipes raised concerns about the integrity of their O-rings and the potential for leaks. They connected deep beneath the engine, making access difficult without removing additional components. After careful inspection and using a camera to document the positioning, we managed to reinsert the pipes, but the risk of leaks loomed large.

Final Steps and Reassembly

After successfully detaching the viscous fan, which was another tricky task, we were left with the water pump ready for replacement. The new pulley needed installation as the old one had become brittle and fell apart during removal.

It was crucial to ensure the bolts securing the water pump were tightened to the manufacturer’s torque specifications, as the aluminium housing requires careful handling to avoid damage.

Testing and Conclusion

Once we replaced the water pump and reassembled the components, we filled the system with coolant and prepared for a test run. Fortunately, everything worked perfectly, and we successfully bled the cooling system—a task that can often be cumbersome.

This repair was a valuable learning experience, emphasising the importance of careful disassembly, documentation, and attention to detail when dealing with complex engine components. By following these steps, we resolved the water pump issue effectively, restoring the vehicle’s cooling system to optimal performance.