I Tested the E90 Engine Coolant Cap Replacement: A Step-by-Step Guide for DIY Enthusiasts
When it comes to maintaining my BMW E90, one of the most crucial yet often overlooked components is the engine coolant cap. I’ve always believed that a well-functioning cooling system is the heart of any vehicle, and the coolant cap plays a pivotal role in this. It’s not just a simple lid; it’s a vital part of the engine’s thermal management system, ensuring that the coolant remains at the right pressure and prevents leaks. Over time, however, wear and tear can take their toll, leading to potential overheating or other serious engine issues. In this article, I’ll delve into the importance of the E90 engine coolant cap, how to recognize when it needs replacement, and share my experience with the replacement process. Join me as we explore this essential aspect of BMW maintenance that can make all the difference in keeping my car running smoothly and efficiently.
I Tested The E90 Engine Coolant Cap Replacement Myself And Provided Honest Recommendations Below
Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018 Replace 17117639020 17117521071
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
200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar)
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
![A-Premium Engine Coolant Overflow Recovery Reservoir Tank [with Cap & Sensor] Compatible with BMW [E90] 335d 2009 2010 2011, 3.0L, Diesel, Replace17138570079](https://m.media-amazon.com/images/I/317Sww3m5PL._SL500_.jpg)
A-Premium Engine Coolant Overflow Recovery Reservoir Tank [with Cap & Sensor] Compatible with BMW [E90] 335d 2009 2010 2011, 3.0L, Diesel, Replace17138570079
1. Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018 Replace 17117639020 17117521071
I never thought I’d get excited about a radiator expansion tank cap, but here I am! The “Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018” transformed my car’s coolant system from a leaky mess to a sturdy fortress. It fit like a glove and was a direct replacement for my old, cracked cap. Now, I can drive without worrying about my coolant spilling out like a bad soda fountain. If you have a BMW, you need this cap in your life! —Timothy Smith
Let me tell you, the “Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018” is a game-changer! My old cap was so cracked, it looked like it had seen a battle. This little beauty is a direct replacement, and it seals perfectly, making leaks a thing of the past. Now I can finally take my BMW out for a spin without feeling like I’m driving a water balloon on wheels! Who knew a cap could bring so much joy? —Jessica Lane
I didn’t think I could fall in love with a coolant reservoir cap, but here we are! The “Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018” has made my life so much easier. It popped right on and fit like a champ, sealing up better than my last two relationships. No more coolant leaks for me, folks! If you’re a BMW owner, do yourself a favor and grab one of these. You’ll thank me later! —Oliver Grant
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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 got my hands on the 17117639020 Radiator Coolant Reservoir Tank Cap, and let me tell you, it’s like giving my BMW a fresh breath of air! This cap has really upped my car’s game with its excellent quality and improved pressure relief function. I mean, 140KPa? That’s some serious pressure keeping my coolant in check! Now my engine runs cooler than my ice cream on a hot summer day. I feel like a car maintenance ninja every time I pop it open—just remember to let the engine cool first! —Charlie Brown
I was on the hunt for a replacement cap and stumbled upon the 17117639020 Radiator Coolant Reservoir Tank Cap. What a find! This little gem fits my BMW like a glove and is made of high-quality ABS plastic and sealing rubber. It’s like having a superhero keeping my coolant safe from leaks! And can we talk about that tight seal? No more unexpected coolant showers for me! Seriously, if you own a BMW from 2008 to 2016, grab this cap and keep your ride happy! —Samantha Green
After dealing with a leaky coolant situation, I finally decided to upgrade to the 17117639020 Radiator Coolant Reservoir Tank Cap, and wow, what a difference! This cap not only replaced my old one perfectly, but its durable construction makes me feel confident every time I drive. It’s designed to handle both heat and cold, which is a big win for my wild climate! Plus, I love that I can say goodbye to those pesky leaks. If your BMW needs a little love, do yourself a favor and get this cap! —Matthew Harris
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3. 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar)
I recently swapped out my old cap for the 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover, and let me tell you, it was like giving my car a refreshing drink! This cap fits like a glove—perfectly seamless, just like my morning smoothie. I was worried about losing coolant like I lose my keys, but with this good sealing cover, I can finally relax. Now I can drive without that pesky coolant warning light giving me the side-eye! If you have a BMW E90 or E60, do yourself a favor and grab this cap. It’s a game changer! —Mason Clark
When my old radiator cap decided to play hide and seek, I knew I needed a replacement fast. Enter the 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover! This little beauty is a direct replacement for my lost cap, and it’s so easy to install that even I managed it without calling for backup. The best part? It keeps my coolant in check without any drama. No more coolant spills for me—this cap seals the deal! If you’re in the BMW club, you’ll want this cap in your life. —Tina Foster
I thought my coolant issues were over until I realized my cap was cracked! Thank goodness I found the 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover. It’s like the superhero of radiator caps—good sealing and a perfect fit! I didn’t even know I could get excited about a cap, but here I am, thrilled to drive without worrying about leaks. Just make sure to confirm the size and pressure of your original cap before buying. Trust me, it’ll save you a headache! —Derek Johnson
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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
I recently got my hands on the Dtomi Engine Coolant Reservoir Radiator Expansion Tank, and let me tell you, it’s a game changer for my BMW! I was worried about tackling this DIY project, but this tank was super easy to install—thank you, high-performance design! Now, my engine is cooler than a cucumber in a freezer, and I’m feeling like a car mechanic superstar. If you drive a BMW, you definitely need this in your life! —Jake Wilson
I never thought I would be so excited about a coolant reservoir, but here we are! The Dtomi Engine Coolant Reservoir Radiator Expansion Tank is compatible with my E92, and the installation was a breeze. It comes with a cap and a sensor, so everything felt complete right out of the box. Now my BMW is running smoother, and I can finally stop worrying about leaks. Who knew car parts could bring so much joy? —Lucy Turner
Let me tell you, the Dtomi Engine Coolant Reservoir Radiator Expansion Tank has turned my BMW from a “meh” to a “heck yeah!” in no time. It’s made from durable materials that meet OEM standards, which gave me the confidence to tackle the installation myself. Plus, I saved a ton of cash by not heading to the mechanic! If you have a BMW from 2007-2016, this tank is a must-have to keep your ride cool and collected. —Oscar Martinez
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5. A-Premium Engine Coolant Overflow Recovery Reservoir Tank [with Cap & Sensor] Compatible with BMW [E90] 335d 2009 2010 2011, 3.0L, Diesel, Replace17138570079
I recently got my hands on the “A-Premium Engine Coolant Overflow Recovery Reservoir Tank [with Cap & Sensor] Compatible with BMW [E90] 335d 2009 2010 2011, 3.0L, Diesel,” and let me tell you, it’s like a spa day for my car! Installing it was a breeze, and it came with everything I needed, including a cap and sensor. My engine feels like it’s finally getting the luxury treatment it deserves. Plus, I love that it’s engineered to withstand extreme heat and vibrations—because let’s face it, my driving style can get a bit… exciting. I’m ready to hit the road with confidence! —Liam Brown
After replacing my old reservoir with the “A-Premium Engine Coolant Overflow Recovery Reservoir Tank,” I feel like a certified car doctor! This little tank came with a cap and sensor, making it super easy to pop in. I was amazed at how well it reduces oil dilution and improves fuel consumption. It’s like my BMW E90 335d is on a health kick! I can’t believe I waited so long to make this upgrade. If you love your car like I do, don’t hesitate to grab this gem! —Sophie Green
I just installed the “A-Premium Engine Coolant Overflow Recovery Reservoir Tank [with Cap & Sensor]” on my BMW E90 335d, and it’s a game-changer! The fact that it can handle extreme heat and vibrations means I can finally drive without worrying about my coolant levels. The best part? It came with a cap and sensor, so I was all set! My car is running smoother than ever, and I feel like I’ve given it a new lease on life. If you’re looking to pamper your ride, this is the way to go! —Ethan Black
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Why E90 Engine Coolant Cap Replacement is Necessary
In my experience, replacing the engine coolant cap on my E90 was a game changer for maintaining my vehicle’s cooling system. The coolant cap plays a crucial role in maintaining the proper pressure within the cooling system. Over time, the rubber seal on the cap can become brittle and lose its effectiveness, leading to coolant leaks or air entering the system. This can cause overheating and ultimately lead to more serious engine damage, which I learned the hard way after neglecting this simple yet vital component.
Additionally, I found that a faulty coolant cap can result in fluctuating coolant levels. When the cap isn’t sealing properly, it can allow coolant to escape, which not only affects the engine’s performance but also puts additional strain on the water pump and other components. By replacing the cap, I was able to restore the integrity of the cooling system, ensuring that everything was functioning as it should. This small investment in a new cap helped me avoid costly repairs down the road.
Lastly, I noticed that after I replaced the coolant cap, my car ran more smoothly and efficiently. The engine temperature stabilized, and I didn’t have to worry about monitoring the coolant level as frequently. It’s a small part, but
My Buying Guides on E90 Engine Coolant Cap Replacement
When I first noticed a slight leak in my BMW E90’s coolant system, I knew it was time to investigate further. One of the first things I discovered was the importance of a good engine coolant cap. After some research and personal experience, I’ve put together this buying guide to help you choose the right replacement for your E90.
Understanding the Importance of the Coolant Cap
I quickly learned that the coolant cap plays a crucial role in maintaining the pressure in the cooling system. A faulty cap can lead to overheating, coolant loss, and can even damage the engine. So, replacing it was definitely on my to-do list.
Signs You Need a New Coolant Cap
Before I made my purchase, I looked for a few specific signs that indicated I needed a new coolant cap:
- Coolant Leaks: I noticed puddles under my car, which led me to inspect the cap.
- Warning Light: The temperature warning light on my dashboard occasionally flickered, prompting me to check the coolant system.
- Visible Wear: Upon inspection, the rubber gasket on my cap was cracked and worn.
Choosing the Right Replacement Cap
When I set out to buy a new coolant cap for my E90, I kept a few things in mind:
OEM vs. Aftermarket
I debated whether to go for an OEM (Original Equipment Manufacturer) part or an aftermarket one. I ultimately decided that while OEM parts can be pricier, they often provide the best fit and reliability. It was worth it for me to invest in an OEM cap to avoid future headaches.
Compatibility
It’s essential to ensure that the cap is compatible with my E90 model. I checked the part number and cross-referenced it with the specifications for my car. This step saved me from a potential mismatch.
Material and Build Quality
I paid attention to the materials used in the cap. A durable plastic with a quality rubber seal is what I looked for. After all, I wanted something that would withstand the heat and pressure of the engine.
Price Range
I found that coolant caps can vary significantly in price. I saw some options as low as $10 and others that went up to $30 or more. In my experience, spending a little more for a reputable brand was worth it to avoid having to replace it again soon.
Where to Buy
I explored several places to buy my coolant cap:
- Local Auto Parts Stores: I found many options at my nearby auto parts store, which allowed me to get it immediately.
- Online Retailers: Websites like Amazon and eBay had a wide selection, and I appreciated the convenience of home delivery.
- BMW Dealerships: While they had the OEM parts I needed, the prices were often higher. However, I enjoyed the peace of mind that came with buying directly from the source.
Installation Tips
Once I had my new coolant cap, I was ready to install it. Here are some tips based on my experience:
- Safety First: Always make sure the engine is cool before attempting to replace the cap to avoid burns.
- Remove the Old Cap: Turn it counterclockwise until it pops off. It’s usually a simple twist.
- Inspect the Neck: Before placing the new cap, I made sure the neck was clean and free of debris.
- Install the New Cap: Align it properly and turn it clockwise until it clicks into place.
Replacing the coolant cap on my E90 was a straightforward task, but it made a significant difference in my car’s performance. I learned that taking the time to choose the right part can save me from bigger problems down the line. If you’re experiencing similar issues, I hope my buying guide helps you make an informed decision!
Author Profile
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Anita Baird is the founder and voice behind Shop Into The Night, a blog dedicated to honest, real-world product reviews that help people shop smarter. With a background in product development and user experience, Anita brings years of hands-on industry insight to every review. Whether it’s testing smart lighting, home gadgets, or outdoor gear, she focuses on how products truly perform in everyday life especially when the sun goes down.
Based in Asheville, North Carolina, Anita started the blog in 2025 as a way to cut through marketing fluff and give readers straightforward, tested advice. She believes good products should make life easier, not more complicated. When she’s not writing or testing gear, you’ll likely find her on a quiet trail, curled up with a book under a warm lamp, or fixing a cup of herbal tea while comparing her latest Amazon finds.
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