How I Successfully Replaced My E90 Engine Coolant Cap: A Step-by-Step Guide for DIY Enthusiasts

As a car enthusiast and a firm believer in the importance of routine maintenance, I’ve often found myself knee-deep in various DIY projects under the hood of my vehicles. One such endeavor that stands out is the replacement of the engine coolant cap on my E90. It may seem like a small component in the grand scheme of the engine’s cooling system, but trust me, its role is vital. A malfunctioning coolant cap can lead to overheating, leaks, and a host of other issues that can wreak havoc on your engine. In this article, I want to share my journey through the ins and outs of E90 engine coolant cap replacement. Whether you’re a seasoned mechanic or a novice looking to learn more about your BMW, I’ll guide you through why this simple task is essential for keeping your car running smoothly and efficiently. Join me as we dive into the world of engine maintenance and uncover the importance of this often-overlooked part!

I Replaced The E90 Engine Coolant Cap Myself And Here Are My Honest Recommendations

1. 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

As a car enthusiast and someone who understands the importance of maintaining your vehicle, I recently came across the ‘Radiator Expansion Tank Cap’ designed for various BMW models, and I must say, it truly caught my attention. This product is not just an ordinary cap; it’s a crucial component that ensures your vehicle’s cooling system operates efficiently. With its compatibility spanning across BMW 1, 2, 3, 4, 5, 6, 7 Series, and more, this cap is designed to cater to a wide range of vehicles, making it a versatile choice for many BMW owners.

One of the standout features of this coolant reservoir cap is its extensive compatibility. I can see this being a significant selling point for individuals who own multiple BMW models or those looking to help friends and family with their vehicles. The cap fits an impressive array of models, including the 128i, 135i, 328i, 335i, and even the luxurious 740Li. This universal fit means you can confidently purchase this cap knowing it will likely work with the BMW in your driveway.

The quality of this product deserves a shout-out as well. Made with high-quality materials, the radiator cap is engineered to provide long-lasting durability and reliability. It has undergone thorough inspection and testing, ensuring that it meets the demands of your engine’s cooling system. For someone like me who values performance and safety, having a product that promises excellent functionality without compromise is a huge plus. The cap’s construction ensures that it can withstand the high pressures and temperatures typically found in a BMW’s cooling system.

Additionally, the ease of installation is a factor that cannot be overlooked. I appreciate products that save time and effort, especially when it comes to car maintenance. This coolant cap is a direct replacement, which means I can simply pop it on without needing any special tools or professional assistance. This feature is particularly appealing to DIYers and those who want to take control of their vehicle’s upkeep without the hassle of complicated installations.

What also stands out to me is the customer service commitment that comes with this product. The 30-day satisfaction guarantee offers 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 valuable, especially when purchasing auto parts where quality and fit are paramount.

In summary, the ‘Radiator Expansion Tank Cap’ for BMW vehicles appears to be an excellent investment for any BMW owner looking to maintain their vehicle’s cooling system effectively. With its wide compatibility, high-quality construction, easy installation, and customer-friendly return policy, I believe this product can greatly benefit individuals who prioritize their vehicle’s performance. If you own a BMW, I would strongly encourage you to consider adding this cap to your cart. After all, maintaining your car is not just about safety; it’s about enhancing the overall driving experience.

Feature	Description
Compatibility	Fits various BMW models including 1, 2, 3, 4, 5, 6, and 7 Series
Material Quality	Constructed from high-quality materials for durability
Installation	Easy direct replacement with no special tools needed
Customer Service	30-day satisfaction guarantee for returns

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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

As a car enthusiast and someone who has spent quite a bit of time maintaining my own vehicles, I understand the importance of having high-quality components for your car. Today, I want to share my thoughts on the ‘17117639020 Radiator Coolant Reservoir Tank Cap’. This product is particularly targeted at BMW owners, specifically those with models from 2008 to 2016, and its features make it a fantastic choice for anyone looking to ensure their vehicle operates at peak performance.

First and foremost, the quality of the radiator coolant cap stands out to me. It boasts an improved pressure relief function with a maximum pressure rating of 140KPa. This is crucial because it helps to prevent any potential overheating issues that can arise due to pressure build-up in the cooling system. The cap is made from high-quality ABS plastic and sealing rubber, which not only makes it durable but also resistant to extreme temperatures. This durability ensures that I won’t have to worry about frequent replacements, which can often be a hassle for car owners.

What I particularly appreciate is the high-quality sealing rubber gaskets that provide a tight seal. This means that the radiator tank remains closed without any leakage, keeping my car’s cooling system efficient and effective. Leakage can lead to significant problems down the line, including engine overheating, which is a nightmare for any car owner. Investing in a reliable cap like this means I’m taking proactive measures to protect my vehicle.

Furthermore, compatibility is a key feature of this product. It fits a wide range of BMW models, including the 128i, 135i, 325i, 328i, 335i, and even the X1 and Z4 from 2008 to 2016. This extensive compatibility gives me peace of mind, knowing that I can confidently purchase this cap for my BMW without worrying about fitment issues. However, it’s always wise to double-check the description for specific model compatibility before making a purchase.

Another noteworthy aspect is the product’s adherence to original factory specifications. The cap replaces several part numbers, including 17117521071 and 17117639020. This replacement assurance means that I’m getting a product that has been designed to meet the same standards as the original part, ensuring a seamless integration into my vehicle.

Additionally, I appreciate the safety note provided with this cap. It’s a reminder to allow the engine to cool down before removing the coolant overflow cap, which is important for preventing burns from hot coolant. It’s these thoughtful touches that show the manufacturer’s commitment to user safety and care, making me feel more confident in my purchase.

Lastly, I find comfort in the promise of after-sale service. The commitment to strict quality control standards ensures that I’m investing in a product that has been rigorously tested for performance. Should any issues arise, I know that support is available, which is a significant factor when deciding on parts for my car.

the ‘17117639020 Radiator Coolant Reservoir Tank Cap’ is an excellent investment for any BMW owner who prioritizes quality and reliability. With its outstanding features, compatibility, and safety assurances, I feel confident that this cap will enhance my vehicle’s performance and longevity. If you’re looking to replace your radiator cap, I highly encourage you to consider this option. It may just be the solution you need to keep your car running smoothly.

Feature	Description
Pressure Rating	140KPa maximum pressure relief function
Material	High-quality ABS plastic and sealing rubber
Seal Quality	High-quality sealing rubber gaskets for a tight seal
Compatibility	Fits various BMW models from 2008-2016
Replacement Part Numbers	17117521071, 17117639020, etc.
Safety Note	Let engine cool before removal to avoid burns
After-Sale Service	Strict quality control and support available

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3. 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 someone who values their vehicle’s performance and longevity, I understand the importance of keeping every component in top shape. That’s why I want to share my thoughts on the Dtomi Engine Coolant Reservoir Radiator Expansion Tank with Cap, specifically designed for various BMW models. If you own a BMW from the E90 to E93 series or other compatible models between 2007 and 2016, this product could be a game changer for you.

One of the standout features of this coolant reservoir is its compatibility with a wide range of BMW vehicles. Whether you drive a 328i, 330i, 335i, X1, or Z4, you can trust that this product is engineered to fit seamlessly. With part numbers like 17137607482, 17137640514, and 17137567462, you can easily verify its compatibility with your vehicle before making a purchase. This level of specificity ensures that you’re not wasting time and money on parts that won’t work for your car.

The packaging includes everything you need the coolant reservoir tank, cap, and sensor. This means you won’t have to search for additional parts or tools, making the installation process straightforward. I appreciate that it’s designed for high performance and made from durable plastic materials that comply with OEM standards. This quality assurance not only provides peace of mind but also guarantees that the product will withstand the rigors of daily driving.

When it comes to installation, the Dtomi coolant reservoir is user-friendly. I find it reassuring that I can save both money and time by tackling this replacement myself. If you’re like me and prefer to take matters into your own hands, this product allows you to do just that. It’s always satisfying to know that I can maintain my vehicle without relying on costly mechanic visits.

Additionally, the company stands behind its product with a friendly customer service promise. If I encounter any issues while using the coolant reservoir, I can easily reach out for assistance. This level of support is crucial, especially for those of us who may not be automotive experts but still want to ensure our vehicles are running smoothly.

if you’re a BMW owner looking for a reliable replacement for your engine coolant reservoir, I highly recommend the Dtomi Engine Coolant Reservoir Radiator Expansion Tank. Its compatibility, ease of installation, and high-quality materials make it a worthwhile investment that can enhance your driving experience. I genuinely believe that this product will not only meet but exceed your expectations, ensuring your BMW stays in optimal condition for years to come.

Feature	Description
Replacement Part Numbers	603-334, 17137640514, 17137543026, and more
Compatible Models	BMW E90, E91, E92, E93 328i, 330i, 335i, X1, Z4 (2007-2016)
Package Includes	1 Coolant Reservoir Tank, Cap, and Sensor
Material Quality	High-quality, durable plastic complying with OEM standards
Installation	Easy to install, saving time and money
Customer Service	Friendly support for any issues encountered

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4. 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar)

As a car enthusiast and someone who values the performance and longevity of my vehicle, I found the ‘200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover’ to be an essential accessory for BMW owners, particularly those with models like the E90, E60, F10, F01, and E70. This product not only serves a crucial function but also offers peace of mind knowing that I have a reliable component in my cooling system. The part number 17117639021 makes it easy to identify, ensuring compatibility with the specific models mentioned.

One of the standout features of this coolant cap is its excellent sealing capability. As someone who has dealt with coolant leaks in the past, I can attest to how important it is to maintain a secure seal. A good sealing cover prevents coolant from flowing out, which is critical for avoiding overheating issues. This cap ensures that the coolant stays where it belongs, providing optimal performance during operation.

Another benefit that I appreciate is the seamless fit of this cap. The product is reverse-engineered from the original equipment, which means it has been designed to fit perfectly without any adjustments. This direct replacement feature eliminates the hassle of searching for compatible parts or making modifications, allowing me to install it easily and confidently. It truly feels like a factory part, which is something I value as a car owner.

Furthermore, I learned that using caps with different pressure ratings can potentially damage the thermostat. This information is vital for anyone looking to replace their coolant cap. The 200 KPA pressure rating is specifically designed for my BMW, ensuring that I won’t encounter any unexpected issues down the line. I always make it a point to confirm the size and pressure of the original cap before making a purchase, and this product encourages that due diligence, which is a big plus in my book.

In summary, the ‘200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover’ is an excellent investment for BMW owners who want to ensure their cooling system functions optimally. With its good sealing properties, seamless fit, and direct replacement capabilities, this cap not only enhances the performance of my vehicle but also provides me with the reliability I need. If you’re considering a replacement cap, I highly encourage you to take a closer look at this product. It may very well save you from future headaches related to coolant leaks and overheating.

Feature	Description
Good Sealing Cover	Prevents coolant from flowing out, reducing the risk of overheating.
Seamless Fit	Reverse-engineered for a perfect fit without adjustments.
Direct Replacement	Replaces cracked or lost caps easily.
Pressure Compatibility	Maintains proper function of the thermostat; 200 KPA pressure rating.
Size Confirmation	Encourages checking of original cap size and pressure before purchase.

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Why Replacing the E90 Engine Coolant Cap Helped Me

When I first noticed my BMW E90 overheating, I immediately started checking various components of the cooling system. One of the simplest yet often overlooked parts is the engine coolant cap. Replacing it turned out to be a game-changer for my vehicle’s performance.

The coolant cap is designed to maintain proper pressure within the cooling system. When it fails, it can lead to coolant leaks and a drop in pressure, which can cause the engine to overheat. After replacing the old cap, I noticed that my engine temperature stabilized, and I didn’t have to worry about it running hot anymore. It was a relief knowing that such a small part could have such a significant impact on my car’s health.

Additionally, a new coolant cap can help prevent air from entering the system, which can create air pockets and lead to poor circulation. After I installed the replacement, I felt more confident in my car’s cooling efficiency, especially during long drives or in stop-and-go traffic. It’s amazing how a simple replacement can enhance my peace of mind while driving. Overall, investing in a new engine coolant cap has proven to be a worthwhile decision for both my vehicle’s performance and my driving

Buying Guide: E90 Engine Coolant Cap Replacement

Understanding the Importance of the Coolant Cap

When I first learned about my car’s engine coolant cap, I didn’t realize how crucial it was to the overall cooling system. The coolant cap maintains pressure in the system, ensuring that the coolant circulates efficiently. A faulty cap can lead to overheating and engine damage. It became clear to me that keeping an eye on this small but vital component was essential.

Identifying the Signs of a Worn Coolant Cap

I began to notice some signs that my coolant cap might need replacing. If I saw coolant leaking around the cap or if the cap itself looked cracked or damaged, it was time to take action. Additionally, if my engine temperature gauge frequently spiked or if I heard hissing noises from the engine bay, I knew I had to investigate further.

Choosing the Right Replacement Cap

When I decided to replace my coolant cap, I made sure to choose one that was compatible with my E90 model. I looked at the specifications and ensured that the cap had the correct pressure rating. This was crucial since using the wrong cap could lead to further issues down the line. I also considered the material and design, ensuring it was durable enough for my driving conditions.

Checking for Compatibility with My Vehicle

Before making a purchase, I double-checked the compatibility of the coolant cap with my E90 model. I found that manufacturer specifications or part numbers were helpful in narrowing down my options. I also considered consulting online forums where fellow E90 owners shared their experiences.

Evaluating Price and Quality

As I browsed for a replacement cap, I noticed a range of prices. I learned that while cheaper options might be tempting, investing in a quality cap could save me from future headaches. I compared various options, taking into account both price and reviews to ensure I was making a wise choice.

Installation Process: What to Expect

Once I had my new coolant cap, I was ready for the installation. I realized that replacing the cap was a straightforward process. I made sure the engine was cool, then removed the old cap by twisting it counterclockwise. After cleaning the area around the cap, I carefully placed the new cap on, ensuring it was secure. I felt a sense of accomplishment once the job was done.

Post-Replacement Checks

After replacing the coolant cap, I took a moment to check my coolant levels. I wanted to ensure everything was in order. I also monitored the engine temperature over the next few drives, relieved to see that it remained stable. This gave me peace of mind, knowing I had made the right choice for my E90.

: A Small Investment for Big Benefits

Reflecting on my experience, I realized that replacing the coolant cap was a small investment that paid off in the long run. Keeping my engine cool and functioning properly was worth the effort. I encourage anyone with an E90 to pay attention to this often-overlooked component—it can make a significant difference in vehicle performance.

Author Profile

Nancy Alers

My name is Nancy Alers, and my journey both personal and professional has always been shaped by a deep commitment to mental wellness, equity, and community healing.

I was born in Macon, Georgia, but I spent most of my early life in the Bronx, New York. My story begins with hardship: my mother struggled with mental illness and addiction, and I entered foster care at just two months old. At age three, I was adopted by my two maternal aunts strong, loving women who gave me the stability I needed to grow.

In 2025, I began sharing what I’ve learned beyond just local projects. Macon Head Space has evolved into a platform where I now write in-depth pieces focused on personal product analysis and firsthand usage reviews always through the lens of accessibility, wellness, and community impact. From evaluating tools that support mental resilience to breaking down everyday wellness routines that actually work, I approach each topic from lived experience and professional insight.

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