BMW manufactures vehicles that are generally known for their build quality and performance. However, there are rare exceptions where BMW chose to implement a less than optimal engineering solution, which ultimately led to serious issues. One such issue that BMW owners might have to deal with is related to the water pump — more specifically, the pulley.
The BMW water pump pulley plays a crucial role in the normal functioning of the water pump, and its failure can result in several problems. In this article, we’ll take a look at everything there is to know about this issue — from models that are most likely to be affected, the symptoms you should look out for, and give you a solution on how you can delay or avoid a water pump pulley failure with your car.
What Does the BMW Water Pump Pulley Do?
The cooling system on your car comprises multiple parts, like the water pump, radiator, and thermostat. One of the core components of the water pump is the pulley that connects the pump to the engine utilizing a serpentine belt. The pulley drives the water pump. Without it, the water pump will not be able to regulate the engine’s temperature, causing it to overheat.
A BMW water pump pulleys are meant to last the life of the car, but they’re known to fail prematurely on some engines. Maintaining the water pump pulley and ensuring it’s in proper working order is essential for its operation and overall engine performance.
Which BMW Cars Have an Issue with the Water Pump Pulley?
Technically, all BMW cars with an injection molded water pump pulley are prone to issues. That said, BMW models produced between 1999 and 2010 have built a notorious reputation for being affected by the problem. The most common culprits include the BMW X5 (E53), BMW 3-Series (E46), and the BMW 5-Series (E39). That’s not to say that other models from the period are not prone to water pump pulley failure — these are just the models that tend to experience the issue more.
The BMW water pump pulley issue is most likely to occur on engines with over 100,000 miles, but it’s not uncommon to see it on models with fewer miles.
What Causes BMW Water Pump Pulley Failure?
A BMW water pump pulley failure can be due to several factors, including regular wear and tear, poor maintenance, or a design flaw. If you own a Bimmer from the period mentioned above, there’s a high chance of failing because of a substandard design. The water pump pulleys used on those cars were made from an injection molded plastic that would get brittle and crack or break over time. A water pump pulley is under a lot of continuous stress from the serpentine belt that runs over it and is bound to undergo wear. The weak plastic construction combined with the load from the pulley belt caused multiple failures on older BMWs.
The pulley could also fail due to a lack of proper maintenance. If you notice that the belt is worn out or the pulley isn’t tightened correctly, it can increase the stress and wear caused to the pulley, eventually causing failure.
What Happens If Your BMW Water Pump Pulley Fails?
The water pump pulley enables the normal functioning of your water pump, so its failure can have serious consequences. The most likely scenario you’ll have to deal with is engine overheating. Since the water pump can no longer circulate coolant through the engine, the engine temperature will rise drastically. An overheating engine can cause damage to its internal components, like the cylinder head and pistons.
With a failed water pump pulley, you might also experience a noticeable drop in performance and coolant leaks around the water pump. If the water pump pulley breaks entirely, it can break into bits that will be sent flying into nearby components, causing further damage.
Can You Drive with a Faulty Water Pump Pulley?
Technically, you can drive with a faulty water pump pulley as long as it hasn’t shattered completely and caused the belt to come off. If not, you can continue driving the car as usual, but we strongly urge that you avoid doing so unless it’s an emergency or if you’re going to a technician to resolve the issue.
Driving with a faulty water pump pulley can cause the engine to overheat, which might result in further damage. It might also cause the engine to stall, leaving you stranded.
How to Fix the BMW Water Pump Pulley Issue?
The most effective solution to a BMW water pump pulley-related issue is to replace the faulty unit with a new one. However, as we mentioned above, a genuine BMW or OEM part, in this case, might not be the most long-term solution, as it’s also made of the same substandard plastic.
In such a case, opting for an aftermarket part from a reliable company is the perfect solution. One such brand worth looking into is URO Parts by A.P.A. Industries. The company makes a CNC-machined aluminum water pump pulley to replace the plastic unit on the stock car. These aluminum units are significantly more reliable and are also lighter. URO Parts also offers a lifetime warranty on them, so you know you don’t have to worry about equipping your BMW with one of these.
When replacing your BMW water pump pulley, a crucial aspect to remember is how much torque you use to tighten it. Overtightening the pulley will restrict its natural motion and cause it to wear out faster. Similarly, if it’s too loose, the belt can move it around and damage it.
Get the Parts You Need from Bimmers.com
BMWs are largely reliable cars, but like every machine, they are bound to face issues every now and then. Getting an aftermarket replacement part instead of an OEM option might solve all your troubles. In other cases, you might learn that sticking to a genuine BMW part is best. No matter which route you choose, you should be able to find exactly what you’re looking for in our store.
Bimmers.com is one of North America’s largest BMW-specific part suppliers and carries everything you’ll need for your BMW — from genuine factory BMW options to reliable aftermarket parts. To find components currently in stock for your Bimmer, just select its year and model number in the site’s shop section.
