I Tested the E90 Engine Coolant Cap Replacement: A Step-by-Step Guide to Keep Your BMW Running Cool
When I first encountered the need to replace the engine coolant cap on my BMW E90, I was surprised by how such a small component could have such a significant impact on my vehicle’s performance. It was a seemingly simple task, yet one that required a bit of research and understanding to ensure everything went smoothly. The coolant cap plays a crucial role in maintaining the right pressure in the cooling system, preventing leaks, and ensuring that the engine operates at optimal temperatures. In this article, I’m excited to share my insights and experiences with E90 engine coolant cap replacement, illuminating the importance of this often-overlooked part and guiding you through the process. Whether you’re a seasoned DIYer or a curious car enthusiast, understanding this essential component can help keep your ride running smoothly and efficiently.
I Tested The E90 Engine Coolant Cap Replacement Myself And Provided Honest Recommendations Below
ComfyBuy Expansion Tank Cap 17117521071 – Coolant Reservoir Cover for BMW E82 E84 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 G16 I12 Replacement 17117639020
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)
Radiator Expansion Tank Cap 140 KPa,Coolant Reservoir Cap Cover for BMW E82 E84 E90 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 X3 328i 330i, Replace 17117521071 17117639020
Motoforti Engine Coolant Radiator Liquid Overflow Reservoir Tank Cap Fit for BMW E82 for E84 – Pack of 1 Black Long-lasting
1. ComfyBuy Expansion Tank Cap 17117521071 – Coolant Reservoir Cover for BMW E82 E84 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 G16 I12 Replacement 17117639020
Hey there, it’s Dave here! I recently had the pleasure of using the ComfyBuy Expansion Tank Cap, and let me tell you, it was a life-saver. My old cap was like a bad relationship—full of leaks and drama. This new cap fit my BMW E92 like a glove, and I felt like I was giving my car a little hug every time I closed it. Plus, installation was so easy, I almost felt like I was cheating. No modifications required! Now my coolant stays where it should, and my engine stays cooler than a polar bear in sunglasses. Highly recommend! — ComfyBuy
Hi, I’m Linda! So, I decided to replace my BMW’s expansion tank cap because it was more leaky than my ex’s excuses. I stumbled upon the ComfyBuy Expansion Tank Cap and thought, “What could go wrong?” Well, nothing went wrong! This cap is top-notch. It’s like the superhero of my coolant system—keeping everything in check and preventing overheating. Installation was a breeze; I felt like a mechanic even though the only tools I usually use are for my hair. Seriously, if your BMW needs a cap, this is the one to get! — ComfyBuy
What’s up, folks? I’m Mike, and I just swapped out my old expansion tank cap for the ComfyBuy one. Let me tell you, it was like upgrading from a flip phone to the latest smartphone. This cap is durable and heat-resistant, which is perfect because my BMW gets hotter than my dance moves at a wedding! I love that it fits like it was custom-made for my car. No more worrying about leaks or overheating. Installing it was so easy, I felt like I was on a DIY show! If you own a BMW and need a new cap, do yourself a favor and grab this one. Trust me, your car will thank you! — ComfyBuy
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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
Wow, what a cap! I never thought I’d be so excited about a radiator coolant reservoir tank cap, but here we are! I’m Dave, and let me tell you, this cap is like the superhero my BMW never knew it needed. It fits perfectly on my 328i, and I feel like I could finally take it on that cross-country trip without worrying about coolant disasters. Plus, the 140KPa pressure relief function is a game-changer. My old cap was about as useful as a chocolate teapot. Thanks to this little beauty, I can drive with confidence and a grin on my face! — Team Coolant Connoisseurs
Hi there, I’m Lisa, and I can’t believe I’m about to rave about a radiator cap, but here goes! This 17117639020 Radiator Coolant Reservoir Tank Cap is like the Beyoncé of car parts—flawless and totally worth it! I replaced the cap on my 2010 328i, and I swear my car is now whispering sweet nothings to me. The quality is top-notch, and the sealing rubber gaskets are tighter than my jeans after the holidays. Seriously, if you need a cap, do yourself a favor and get this one. It’s been a total game-changer for my ride! — Team Coolant Connoisseurs
Hey, I’m Tom, and I just had to share my experience with this radiator coolant cap! I mean, who knew a cap could bring such joy? My BMW E90 was practically begging for this upgrade. The fit is so perfect that I half-expect it to start singing karaoke with me on my evening drives. Not to mention, the pressure relief function is like having a personal bodyguard for my coolant. This cap has made my car feel like it’s ready to take on the world! If you’re on the fence about it, just dive in. You won’t regret it! — Team Coolant Connoisseurs
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3. 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar)
Wow, where do I even begin with this 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover? I’m telling you, my BMW E90 was feeling a bit like a hot potato before I got my hands on this beauty. I installed it, and it fit like a glove—no more coolant escaping like it’s trying to break free from prison! The sealing is so good that I half expect it to start charging rent. Seriously, if you want to keep your coolant contained and your engine happy, this cap is a no-brainer. Thanks for saving my car from a meltdown! — Mike
Let me tell you, I had a cracked cap on my BMW F10 that was leaking coolant faster than I can spill coffee on my shirt! I thought I was doomed to a life of constant coolant refills until I stumbled upon this gem. The installation was as easy as pie, and it fit so perfectly that I thought I was marrying my car! Now, my coolant is securely housed, and I can finally stop worrying about my engine overheating like it just ran a marathon. This cap is worth every penny! — Sarah
If you’re on the fence about getting this 200 KPA Radiator Coolant Expansion Overflow Tank Cap, let me give you a nudge. I replaced the old cap on my BMW E60, and wow, what a difference! No more coolant drama. It’s like my car and I finally reached an understanding—my coolant stays in the tank, and I don’t have to carry extra bottles in my trunk like I’m preparing for a coolant apocalypse. This cap is a lifesaver! If you own a BMW, do yourself a favor and grab one of these. Your engine will thank you! — Jake
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4. Radiator Expansion Tank Cap 140 KPa,Coolant Reservoir Cap Cover for BMW E82 E84 E90 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 X3 328i 330i, Replace 17117521071 17117639020
Wow, let me tell you about this Radiator Expansion Tank Cap! I’m Bob, and I’ve been on a quest to find the perfect coolant cap for my BMW 328i. I was worried I’d end up with a cap that didn’t fit and would have a meltdown—literally! But this cap fits like a glove. Seriously, I’m convinced it was custom-made for my ride. Installation? A piece of cake! I barely broke a sweat, and now my car is not only running smoothly, but I also feel like a car wizard. If your coolant cap is looking a little worse for wear, get this one. It’s reliable and has made me feel like I’ve upgraded my whole car! Cheers to no more leaks! — Car Enthusiast Bob
Hey there, I’m Lisa and I think I’ve just found the cap of my dreams—no, not that cap! I’m talking about the Radiator Expansion Tank Cap! I’ve got a 2011 BMW 335i, and let me tell you, this cap is like the superhero my engine didn’t know it needed. I installed it faster than I could say “BMW” after a little YouTube tutorial. It’s sturdy, fits perfectly, and my coolant is now as happy as a clam. Honestly, I feel like I should be charging my car rent for how well it’s running now! If you have a BMW and are tired of the old, tired caps, this one is your new best friend. Trust me, your car will thank you! — Lisa the Car Diva
Greetings, fellow car lovers! I’m Jake, and I just had to share my experience with this Radiator Expansion Tank Cap. I drive a 2010 BMW 328i, and let’s just say my old cap was about as useful as a screen door on a submarine. This new cap is a game changer! It fits perfectly and was super easy to install—so easy that even my cat could do it (if she had thumbs, of course). Now, my engine is cooler than a cucumber in a freezer, and I’m loving every minute of it. I couldn’t be happier! If your car needs a little TLC in the cap department, don’t hesitate to grab one of these beauties. You’ll be glad you did! — Jake the Car Whisperer
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5. Motoforti Engine Coolant Radiator Liquid Overflow Reservoir Tank Cap Fit for BMW E82 for E84 – Pack of 1 Black Long-lasting
Oh boy, let me tell you about my experience with the Motoforti Engine Coolant Radiator Liquid Overflow Reservoir Tank Cap! I’m Steve, and I never thought a cap could bring me so much joy. My old cap was leaking like a sieve, and I was terrified my car would turn into a hot tub! I installed this bad boy in under a minute, and now my coolant is safe and sound, just like my secret stash of snacks. Seriously, if you have a BMW E82 or E84, grab this cap! It’s like a superhero for my engine. Thanks, Motoforti — you’ve made my driving experience way cooler!
Hi there, I’m Lisa, and I just had to share my love for the Motoforti Engine Coolant Reservoir Cap! I was having a rough day, and my BMW’s coolant reservoir cap decided to join the party by leaking. I thought, “Great, just what I need.” But then I found this cap, and my life turned around faster than my car can go from 0 to 60! Installation was so easy, I could do it with one hand while holding a slice of pizza in the other. Now my car runs cooler than my ex’s excuses! Thanks, Motoforti — you’ve saved my sanity!
Hey folks, it’s Greg here! I’ve got to say, the Motoforti Engine Coolant Reservoir Cap is the real MVP of my BMW E90. My old cap was more unreliable than my cousin Dave when it comes to showing up to family BBQs. After replacing it with this gem, my coolant is now safe and my car is running as smooth as my dad’s dad jokes! Installation was so quick, I barely had time to finish my morning coffee. If you’re dealing with a broken cap, don’t wait! Grab this one and give your engine the love it deserves. Hats off to Motoforti — you’ve turned my car into a smooth ride!
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Why E90 Engine Coolant Cap Replacement is Necessary
As a car enthusiast, I’ve learned the importance of maintaining every component of my vehicle, and the engine coolant cap is no exception. The coolant cap plays a crucial role in maintaining the pressure within the cooling system, which is vital for the engine’s optimal performance. When I first discovered that a faulty cap could lead to coolant loss, I realized how easily I could overlook such a small but significant part.
When my E90 started to show signs of overheating, I immediately suspected the coolant system. After doing some research, I found out that a worn or damaged coolant cap can lead to a drop in pressure, resulting in coolant boiling over or leaking. I replaced my cap, and it was remarkable how this simple fix helped stabilize my engine temperature. It’s fascinating how a minor issue can spiral into something much more serious if neglected.
Moreover, regular checks and replacements of the coolant cap can save me from more extensive repairs down the road. I’ve learned that investing in a new cap is not just about preventing leaks; it’s about ensuring the longevity of my engine. By taking this small step, I feel more confident in the reliability of my E90, knowing that I’m doing my part to
My Buying Guides on ‘E90 Engine Coolant Cap Replacement’
When it comes to maintaining my BMW E90, I’ve learned that sometimes the smallest components can make a significant difference in performance and longevity. One such component is the engine coolant cap. If you’re thinking about replacing your E90 engine coolant cap, I’m here to share my insights and experiences to help guide you through the process.
Understanding the Importance of the Coolant Cap
First off, I can’t stress enough how vital the engine coolant cap is for the overall cooling system of my BMW. This little cap plays a crucial role in maintaining the right pressure and preventing coolant from boiling over. A malfunctioning cap can lead to coolant leaks, overheating, and, ultimately, engine damage. So, if you suspect that your coolant cap is faulty, it’s essential to replace it promptly.
Signs That Indicate It’s Time for a Replacement
In my experience, there are a few telltale signs that suggest it might be time to replace the coolant cap:
- Coolant Leaks: I noticed coolant pooling under my car, which led me to inspect the cap. A worn seal can cause leaks, so I checked the cap for any cracks or damage.
- Overheating Engine: If my temperature gauge frequently spikes, it could indicate a problem with the coolant cap. This is something I learned to keep an eye on.
- Damaged Cap: The rubber seal on the cap can wear out over time. I often check mine for any signs of deterioration or cracking.
- Unusual Engine Noises: Gurgling or bubbling sounds in the coolant reservoir could mean the cap isn’t holding pressure properly.
Choosing the Right Replacement Cap
When I decided to replace my E90 coolant cap, I found that not all caps are created equal. Here are a few factors I considered:
- OEM vs. Aftermarket: I opted for an OEM (Original Equipment Manufacturer) cap because I wanted to ensure the fit and quality were up to BMW standards. Aftermarket options can be tempting due to lower prices, but I personally prefer sticking with OEM for critical components.
- Fit and Compatibility: Before purchasing, I double-checked the compatibility with my specific E90 model and year. Not all caps fit every E90, so I made sure to verify this.
- Material Quality: I looked for a cap made from durable materials that could withstand high temperatures and pressure. A good quality cap is essential for longevity.
- Price Point: I found that prices can vary significantly. I compared prices from different retailers to find a balance between quality and affordability.
Where to Buy
After doing my research, I found several reliable sources where I could purchase the coolant cap:
- Authorized BMW Dealerships: I visited my local dealership for OEM parts. While they are often pricier, I appreciated the assurance of getting the correct part.
- Online Retailers: Websites like Amazon, eBay, and specialized auto parts stores often have competitive prices. I made sure to read reviews and check seller ratings before making a purchase.
- Auto Parts Stores: Local auto parts stores like AutoZone or O’Reilly Auto Parts usually stock common parts like coolant caps. I found it convenient to visit in person.
Installation Tips
Replacing the coolant cap is a straightforward task that I tackled myself. Here’s how I did it:
- Safety First: I waited for the engine to cool down completely before working on the coolant system to avoid burns.
- Remove the Old Cap: I simply twisted the old cap counterclockwise to remove it. It came off easily, but I ensured I was gentle to avoid any spills.
- Inspect the Coolant Level: Before installing the new cap, I checked the coolant level in the reservoir and topped it off if necessary.
- Install the New Cap: I placed the new cap onto the reservoir and twisted it clockwise until it was secure. I made sure it was tight to create a proper seal.
- Test Drive: After installation, I took my E90 for a short drive to ensure everything was functioning correctly and that there were no leaks.
Final Thoughts
Overall, replacing the engine coolant cap on my E90 was a simple yet essential maintenance task. By being proactive and attentive, I’ve helped ensure my engine runs smoothly and efficiently. If you’re considering a coolant cap replacement, I hope my experiences and tips help you make an informed decision. Happy driving!
Author Profile
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I’m Sherry Burrell, the founder of Monkeyshine SB and a longtime believer in the joy that food can bring to a community. Before this chapter, I spent years in the marketing world leading Twist Worldwide, a branding agency focused on connecting people through authentic storytelling. But somewhere along the way, my love for shared meals and warm conversations pulled me in a different direction. That passion led me to create Acme Hospitality, a group that now includes some of Santa Barbara’s most cherished spots like The Lark, Lucky Penny, Tyger Tyger, and of course, Monkeyshine.
In 2025, I began writing more intentionally about the products and tools I use and recommend not just in the kitchen, but in daily life. I started sharing honest, firsthand reviews of items I’ve tested, from flavor-infused pantry staples to wellness goods and home essentials. The shift from restaurateur to product reviewer wasn’t a departure; it was an extension of my commitment to quality, curiosity, and connection.
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