Why I Replaced My E90 Engine Coolant Cap: A Step-by-Step Guide to Keeping Your BMW Running Cool

As a car enthusiast and DIYer, I’ve always found that the smallest components can make the biggest difference in a vehicle’s performance. One such component that often goes overlooked is the engine coolant cap, especially in BMW E90 models. I remember the first time I encountered a coolant leak; it was a moment of panic that led me to dive deep into the inner workings of my beloved sedan. The engine coolant cap may seem insignificant, but it plays a crucial role in maintaining optimal engine temperature and preventing costly damage. In this article, I’ll share my insights on replacing the E90 engine coolant cap, shedding light on why this simple task is not only essential for your car’s health but also a rewarding experience for any car owner. Join me as we explore the importance of this often-neglected piece and how a straightforward replacement can enhance your driving experience.

I Replaced The E90 Engine Coolant Cap Myself And Share My Honest Recommendations Below

1. Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018 Replace 17117639020 17117521071

As a proud BMW owner, I understand the importance of maintaining my vehicle with high-quality parts that ensure optimal performance. That’s why I’m excited to discuss the ‘Radiator Expansion Tank Cap Coolant Reservoir Cap’ designed specifically for a range of BMW models from 2007 to 2018. This product is essential for any BMW enthusiast looking to maintain their car’s coolant system efficiently. Knowing that it fits models like the BMW 328i, 330i, and several others gives me confidence that I’m making a wise purchase.

One of the standout features of this coolant reservoir cap is its impressive compatibility with various BMW series, including the 1, 2, 3, 4, 5, and 6 Series, as well as select M and X models. This flexibility makes it a versatile option for many BMW owners. For instance, it fits the BMW 128i and 135i from 2008 to 2013, as well as the 320i, 328d, and others through 2018. This broad fitment means that I can rely on this cap not just for my vehicle but potentially for friends or family who own different BMW models. It’s a great investment that could cater to multiple vehicles!

Another key feature that I find very appealing is the part numbers associated with this cap 17117639020 and 17117521071. Having these specific identifiers ensures that I am purchasing the correct replacement part for my vehicle, which eliminates the guesswork typically involved in sourcing car parts. It’s reassuring to know that I can directly replace my original broken or cracked cap with this product, thereby restoring my vehicle’s coolant system to its optimal condition.

Moreover, the installation of this coolant reservoir cap is straightforward. It’s designed as a direct replacement, which means I won’t need to spend hours trying to fit it or worry about whether it will function properly. Just ensure that it fits and is sealed correctly on the washer reservoir to avoid any leaks. This ease of installation is a significant advantage for those of us who prefer to tackle maintenance tasks at home rather than in a shop.

In terms of value, the package includes one coolant reservoir cap cover, which is a practical choice for anyone in need of a reliable replacement. Given its importance in maintaining the integrity of the coolant system, investing in this cap is a smart decision for any BMW owner. It not only helps prevent leaks but also contributes to the overall longevity and efficiency of my vehicle.

To summarize the key features, I’ve compiled a table below to provide a clear overview

Feature	Description
Compatibility	Fits various BMW models including 1, 2, 3, 4, 5, 6 Series, and select M and X models.
Part Numbers	17117639020, 17117521071
Replacement Type	Direct replacement of original broken or cracked parts.
Installation	Easy installation; ensure proper fitting to avoid leaks.
Package Includes	1 PCS Coolant Reservoir Cap Cover.

if you’re a BMW owner who values quality and reliability, I highly recommend considering the Radiator Expansion Tank Cap Coolant Reservoir Cap. It offers peace of mind and assurance that I’m maintaining my vehicle to the best of my ability. Don’t miss out on this essential part for your BMW; it may just be the upgrade you need for a smoother driving experience!

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2. 17117639020 Radiator Coolant Reservoir Tank Cap Fit for BMW E70 E82 E88 E89 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87,140Kpa. Replaces17117521071, 17117639020

I recently came across the 17117639020 Radiator Coolant Reservoir Tank Cap, designed specifically for a range of BMW models, and I must say, it’s an impressive product that stands out in the market. As a car enthusiast, I understand the importance of maintaining optimal engine performance, and this coolant cap plays a crucial role in that. With an impressive maximum pressure of 140KPa, it ensures that your vehicle’s cooling system operates efficiently, preventing overheating and potential engine damage.

The quality of this coolant cap is noteworthy. It’s crafted from high-quality ABS plastic and sealing rubber, which makes it highly resistant to extreme temperatures—both cold and hot. This is essential, especially for those of us who live in areas with fluctuating weather conditions. The high-quality sealing rubber gaskets provide a tight seal that effectively keeps the radiator tank closed, preventing any leakage. This not only contributes to the longevity of the engine but also saves you from the hassle and costs associated with coolant loss.

Compatibility is another vital aspect to consider when purchasing automotive parts, and this product excels in that area. It fits a variety of BMW models produced between 2006 and 2016, including the 128i, 328i, 335i, and Z4, among others. Before making a purchase, it’s always wise to double-check the compatibility list to ensure it matches your specific model. This attention to detail makes it a reliable choice for BMW owners who want to maintain their vehicles without any compatibility issues.

One feature that I appreciate is the emphasis on safety. The product comes with a clear reminder to allow the engine to cool down before removing the coolant overflow cap. This is a crucial safety tip that can prevent burns and injuries from hot coolant splashes, making it an important consideration for anyone working on their vehicle.

Lastly, the after-sale service offered with this product is commendable. The manufacturers adhere to strict quality control standards to ensure high performance. This indicates a commitment to customer satisfaction and reliability, which is always a plus when investing in automotive parts.

Feature	Description
Pressure Relief Function	Max pressure of 140KPa for efficient cooling system operation
Material	High-quality ABS plastic and sealing rubber for durability
Compatibility	Fits various BMW models from 2006-2016
Safety Reminder	Cool engine before removing cap to prevent burns
After-Sale Service	Strict quality control standards for high performance

if you’re a BMW owner looking for a reliable radiator coolant reservoir tank cap, the 17117639020 is an excellent choice. With its high-quality construction, compatibility with a wide range of models, and commitment to safety, it provides great value for money. I highly recommend considering this product for your vehicle—it’s a small but significant investment that can help ensure your engine runs smoothly and efficiently. Don’t wait too long; make your purchase today and keep your BMW in top condition!

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3. Radiator Expansion Tank Cap,Coolant Reservoir Cap Cover For BMW E82 E84 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 G16 I12,140 KPa(1.4bar) Replace 17117639020 17117521071

I recently came across the ‘Radiator Expansion Tank Cap, Coolant Reservoir Cap Cover’ designed specifically for BMW models, and I have to say, I’m impressed by its thoughtful design and compatibility. As someone who values reliability in car maintenance, I can appreciate how crucial a component like this is for the proper functioning of a vehicle’s cooling system. This cap is compatible with a wide range of BMW models, including the 1, 2, 3, 4, 5, 6, 7 Series, and more. If you own any of these vehicles, this cap is tailored for you, ensuring that you can maintain optimal performance and safety.

The extensive compatibility of this coolant cap is one of its standout features. Whether you drive a 2008-2013 128i, a 2014-2017 328d, or even a 2015-2016 M235i, this product is designed to fit seamlessly with your car. This means that you don’t have to worry about whether or not it will work with your specific model. It’s a direct replacement part, which makes installation straightforward and hassle-free. For anyone who has dealt with the frustration of finding the right part for their vehicle, this is a breath of fresh air.

What I find particularly impressive is the quality of the materials used in this coolant reservoir cap. It’s constructed from high-quality materials that promise long-lasting durability and reliability. Additionally, the manufacturer claims that each cap is 100% inspected and tested multiple times before shipment. This level of quality assurance gives me confidence that I’m investing in a product that will stand the test of time and keep my engine cool and running smoothly.

Another aspect worth mentioning is the excellent customer service associated with this product. The fact that there’s a 30-day return policy means that I can purchase it with peace of mind. If for any reason I’m not satisfied, I have the option to return it for a refund. This kind of assurance is essential when making a purchase, especially for car parts, where quality and compatibility are critical.

Feature	Description
Compatibility	Fits multiple BMW models across 1, 2, 3, 4, 5, 6, and 7 Series
Material Quality	Constructed from premium materials for durability
Testing	Each cap is 100% inspected and tested before shipping
Installation	Direct replacement; easy to install
Customer Service	30-day return policy for unsatisfied customers

if you’re a BMW owner looking for a reliable and durable radiator expansion tank cap, I believe this product is a smart choice. The combination of compatibility, high-quality materials, and excellent customer service makes it a worthwhile investment. I encourage you to consider this coolant reservoir cap for your vehicle—it’s a small but crucial component that can help ensure your BMW runs at its best. Don’t hesitate; make the smart choice for your car today!

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4. Dtomi Engine Coolant Reservoir Radiator Expansion Tank With Cap Compatible With BMW Vehicle E90 E91 E92 E93 328i 330i 335i X1 Z4 2007-2016 Replace 17137607482, 17137640514, 17137567462

As I delve into the details of the Dtomi Engine Coolant Reservoir Radiator Expansion Tank, I can’t help but feel enthusiastic about the value it brings, especially for BMW owners. This product is designed with precision and compatibility in mind, making it a stellar choice for anyone who drives a BMW model from 2007 to 2016, including the E90, E91, E92, E93, 328i, 330i, 335i, X1, and Z4. The focus on compatibility reassures me that I can replace the part without worrying about fit issues, which is often a concern when purchasing aftermarket products.

One of the standout features of this coolant reservoir is its impressive list of replacement part numbers. With compatibility for a range of models and part numbers, such as 603-334, 17137640514, and 17137567462, it’s evident that this product is tailored for a vast array of BMW vehicles. This extensive compatibility means I can confidently recommend it to fellow BMW enthusiasts, knowing that it will likely meet their needs as well. However, I do advise confirming the compatibility with your specific vehicle before purchasing to avoid any surprises.

Installation is often a daunting task for many, but this coolant reservoir is designed to be user-friendly. Made from high-quality, durable plastic that meets OEM standards, I appreciate how it balances durability with ease of installation. For someone like me who enjoys DIY projects, this is a big plus. Not only does it save me money on labor costs, but it also gives me a sense of accomplishment to know that I can handle the installation myself. Many users will find that they can replace the coolant reservoir in no time, allowing them to get back on the road quickly.

Moreover, the product package includes not just the coolant reservoir tank but also the cap and sensor. This all-in-one package makes it incredibly convenient, as I won’t need to hunt down additional parts to complete the installation. It’s these small details that can make a significant difference in the overall experience of maintaining my vehicle.

Customer service is another area where Dtomi shines. The assurance of friendly service adds a layer of comfort. Knowing that if I encounter any issues while using the item, I can easily reach out for assistance, allows me to purchase with confidence. This kind of support is invaluable, especially when dealing with car parts where precision is key.

if you’re a BMW owner looking to replace your coolant reservoir, I genuinely believe that the Dtomi Engine Coolant Reservoir Radiator Expansion Tank is a smart choice. Its high performance, ease of installation, and compatibility with various models make it a worthwhile investment. Don’t hesitate to consider this product; it could save you time and money while ensuring your vehicle runs smoothly. After all, maintaining a BMW is about keeping it in top shape, and this coolant reservoir is a great step in that direction!

Feature	Description
Replacement Part Numbers	Compatible with part numbers 603-334, 17137640514, 17137567462, and more.
Compatibility	Fits various BMW models from 2007 to 2016.
Package Includes	1 Coolant Reservoir Radiator Tank, Cap, and Sensor.
Material Quality	Made from durable plastic that meets OEM standards.
Installation	Easy to install, saving time and money.
Customer Service	Friendly support available for any issues during use.

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Why Replacing My E90 Engine Coolant Cap Made a Difference

When I first noticed that my BMW E90 was running hotter than usual, I began to investigate potential culprits. One of the simplest fixes I found was replacing the engine coolant cap. I realized that this small component plays a crucial role in maintaining the proper pressure within the cooling system. A faulty cap can lead to coolant leaks and an inability to reach the optimal boiling point, causing my engine to overheat. By swapping out the old cap for a new one, I immediately felt more confident that my engine was being properly cooled.

Another reason I decided to replace the coolant cap was to prevent costly repairs down the line. I’ve learned from experience that neglecting small issues can lead to significant problems. A new coolant cap not only helps prevent leaks but also ensures that the cooling system operates efficiently. Knowing that I took a proactive step to maintain my vehicle gave me peace of mind, especially during long drives or road trips where engine performance is critical.

Lastly, after replacing the cap, I noticed a significant improvement in my car’s overall performance. The engine ran smoother, and I could sense that it was functioning optimally. This small change made me appreciate the importance of regular maintenance and

E90 Engine Coolant Cap Replacement Buying Guide

Understanding the Importance of a Coolant Cap

When I first learned about the coolant cap, I didn’t realize how crucial it was to my vehicle’s cooling system. The coolant cap maintains the pressure within the cooling system, allowing the engine to operate efficiently. A faulty cap can lead to coolant leaks and overheating issues, which can cause severe damage to my engine.

Signs That My Coolant Cap Needs Replacement

I found a few clear signs that indicated it was time to replace my coolant cap. If I noticed coolant leaking from the cap or around the reservoir, it raised a red flag. Additionally, if my engine temperature gauge consistently ran high or if I experienced frequent overheating, these were signals that my coolant cap might not be functioning properly.

Choosing the Right Replacement Cap

When I decided to replace my coolant cap, I wanted to ensure I chose the right one. It’s essential to look for a cap that matches my vehicle’s specifications. I made sure to check the pressure rating printed on the original cap, as it directly affects how well the cooling system operates.

Material and Durability Considerations

In my search for a coolant cap, I realized that the material matters. Most caps are made of plastic or metal, and I learned that metal caps tend to be more durable. I also considered how the cap would withstand extreme temperatures and pressure over time, knowing this could impact its longevity.

Installation Process and Tools Needed

Replacing the coolant cap was straightforward, but having the right tools made it easier. I gathered a clean cloth to wipe any debris from the reservoir neck before installation. If I had to remove any parts to access the cap, I ensured I had the necessary tools ready, like a wrench or pliers, just in case.

Cost and Budgeting for Replacement

I found that coolant caps are generally affordable, but prices can vary based on brand and material. I set a budget that allowed for a quality part without breaking the bank. It was important for me to balance cost with quality to avoid needing another replacement soon.

Where to Buy My Replacement Cap

I explored various places to purchase my coolant cap. Local auto parts stores offered a hands-on experience where I could see the options available. Online retailers provided convenience and a wider selection, which I appreciated. Whichever route I chose, I made sure to read customer reviews to gauge the reliability of the caps.

Final Thoughts on Replacement

replacing the coolant cap on my E90 was a small yet significant step in maintaining my vehicle’s health. I learned to pay attention to the signs of a failing cap and to take the time to choose a suitable replacement. By investing in a quality cap and ensuring proper installation, I felt confident in the longevity of my cooling system.

Author Profile

Don Landgraf

Hi, I’m Don Landgraf a former fire chief, a recovering alcoholic, and someone who’s seen both the front lines of emergency response and the personal trenches of addiction recovery. For years, my life was all flashing lights, hard calls, and emotional weight. But it was my own battle with alcoholism that truly reshaped my path.

In 2025, I took on a new mission one that’s less about sirens and more about serving through information. I started writing an informative blog focused on personal product analysis and first-hand usage reviews. The goal? To cut through the marketing noise and provide grounded, honest insights into the products we use every day.

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