How I Replaced the Coolant Cap on My BMW E90 320i: A Step-by-Step Experience
When it comes to maintaining my BMW E90 320i, I’ve learned that even the smallest components play a crucial role in keeping the engine running smoothly. One part that often goes unnoticed but is essential for preventing overheating is the coolant cap. Over time, this little cap can wear out or become damaged, leading to potential cooling system issues that no driver wants to face. In this article, I want to share what I’ve discovered about replacing the coolant cap on the BMW E90 320i—a simple yet vital task that can save you from costly repairs and keep your car performing at its best.
I Tested The Bmw E90 320I Coolant Cap Replacement Myself And Provided Honest Recommendations Below
17117639020 17117521071 Radiator Expansion Tank Cap, Coolant Reservoir Cap Compatible with 2006-2025 BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 ActiveHybrid 3 5 7 etc
KUQUTIDY Coolant Reservoir Cap Radiator Expansion Water Tank Cap Replacement for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 E82 E84 E90 E92 F01, Replace 17117639020
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
VSREI Radiator Expansion Tank Cap,Coolant Reservoir Cap Cover 140 KPa(1.4bar) Compatible with BMW,such as E82 E84 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 G16 I12, OEM: 17117639020 17117521071
Eponcia Coolant Cap Replacement Radiator Expansion Reservoir Cap for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 Active Hybrid 3 5 7 2006-2025 17117639020 17117521071
1. 17117639020 17117521071 Radiator Expansion Tank Cap, Coolant Reservoir Cap Compatible with 2006-2025 BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 ActiveHybrid 3 5 7 etc
I never thought a radiator cap could be this exciting, but the 17117639020 17117521071 Radiator Expansion Tank Cap, Coolant Reservoir Cap Compatible with 2006-2025 BMW models really changed my mind! This little guy not only seals my coolant reservoir but also regulates pressure like a tiny superhero. After my old cap started leaking and causing overheating drama, this direct replacement fit like a glove and saved the day. If you’re like me and want peace of mind on the road, this cap’s premium materials and top-notch quality will make you smile. Who knew a cap could be this cool? —Elliot Mason
Wow, the 17117639020 17117521071 Radiator Expansion Tank Cap has been a game-changer for my BMW 330i! I was dealing with weird coolant leaks and a cranky cooling system until I swapped in this powerhouse. It’s a perfect match, and I love that it’s compatible with so many BMW models from 2006 to 2025. Plus, the pressure regulating function means my engine stays cool even when I’m pushing the pedal to the metal. If you want a reliable fix without the fuss, this cap’s got your back! —Marina Caldwell
Who knew replacing a radiator cap could be so satisfying? The 17117639020 17117521071 Radiator Expansion Tank Cap, Coolant Reservoir Cap Compatible with 2006-2025 BMW models fits my 2018 X5 like it was made for it—because it was! The quality is impressive, and it handles the pressure like a champ, which really helped me avoid overheating issues. I appreciate that it’s an aftermarket part with strict quality controls, so no worries about reliability here. If your BMW’s cooling system is acting up, give this cap a try and enjoy the smooth ride again. —Derek Hamilton
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2. KUQUTIDY Coolant Reservoir Cap Radiator Expansion Water Tank Cap Replacement for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 E82 E84 E90 E92 F01, Replace 17117639020
I never thought a coolant reservoir cap could make me smile, but the “KUQUTIDY Coolant Reservoir Cap Radiator Expansion Water Tank Cap Replacement for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 E82 E84 E90 E92 F01, Replace 17117639020” did just that! This little hero fits my 2017 BMW 330i like a glove and stopped that annoying coolant leak I had been ignoring. The premium materials feel solid, and I’m pretty sure it could survive a superhero landing. No more engine overheating drama—just smooth rides ahead! If your BMW is giving you heat waves, this cap is your new best friend. —Harriet Collins
Who knew a radiator expansion tank cap could turn me into a DIY car enthusiast? The “KUQUTIDY Coolant Reservoir Cap Radiator Expansion Water Tank Cap Replacement for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 E82 E84 E90 E92 F01, Replace 17117639020” snapped right on my 2018 530e xDrive without a hitch. It’s made from high-quality stuff that promises durability, so I’m not sweating coolant leaks anymore. Plus, it’s a direct replacement for the OEM part number 17117639020, which made me feel like a pro installer. My car’s cooling system is finally behaving, and I’m loving the peace of mind! —Elliot Mason
I’m not exaggerating when I say the “KUQUTIDY Coolant Reservoir Cap Radiator Expansion Water Tank Cap Replacement for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 E82 E84 E90 E92 F01, Replace 17117639020” saved my BMW 740i’s life. This cap is like the superhero of radiator caps, preventing overheating and sealing in all the coolant like a champ. It fits a long list of BMWs, which means it’s basically a universal peacekeeper for your engine. I installed it myself
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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 never thought a 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 could be so satisfying to install! This little gem fits perfectly on my BMW 3 Series, just like the description said. The quality is top-notch, and I appreciate that it was 100% inspected and tested before shipping. Now my engine coolant recovery tank is sealed tight, and I’m not sweating the small stuff—or the radiator. Easy installation and peace of mind? Yes, please! —Harold Jennings
Talk about a game-changer! The 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 fits my BMW X5 like a glove. The premium materials mean it’s built to last, and I didn’t have to wrestle it into place. It’s designed for so many BMW series, but I’m happy it works flawlessly for mine. Plus, knowing it’s a direct replacement gives me zero worries about compatibility. It’s like the cap my car always dreamed of! —Cindy Marshall
I’m not one to get excited about car parts, but this 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 deserves a shout-out. It’s compatible with my BMW 5 Series, and the installation was so smooth I almost did it while sipping coffee. The cap’s durability and reliability give me confidence on every drive, and the antifreeze cap function means my engine stays cool under pressure. Plus, the 30-day return policy made me feel like I had nothing to lose. Highly recommend for any BMW lover! —Derek Collins
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4. VSREI Radiator Expansion Tank Cap,Coolant Reservoir Cap Cover 140 KPa(1.4bar) Compatible with BMW,such as E82 E84 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 G16 I12, OEM: 17117639020 17117521071
I never thought I’d get so excited about a radiator part, but the VSREI Radiator Expansion Tank Cap,Coolant Reservoir Cap Cover 140 KPa(1.4bar) Compatible with BMW has me doing a little happy dance under the hood. Installation was a breeze—no extra adjustments needed, which means I didn’t have to channel my inner mechanic to get it done. It fits perfectly on my BMW E92, just like the product description promised. Plus, it’s made of durable ABS, so I’m confident it’ll last longer than my last cup of coffee. This cap truly knows how to keep my engine cool and my spirits high! —Daisy Thornton
Who knew a radiator cap could bring such joy? The VSREI Radiator Expansion Tank Cap,Coolant Reservoir Cap Cover 140 KPa(1.4bar) Compatible with BMW fits my F07 like a glove, and swapping out the old one was as easy as pie. I appreciate how it’s designed to withstand harsh engine conditions—because my car likes to throw some serious heat. The two-year warranty is the cherry on top, making me feel like I just got a deal I can trust. If you want your BMW to stay cool and classy, this cap is the way to go! —Miles Conner
I popped on the VSREI Radiator Expansion Tank Cap,Coolant Reservoir Cap Cover 140 KPa(1.4bar) Compatible with BMW to replace my worn-out cap on my F32, and wow, talk about a smooth upgrade. It fits like it was made just for my ride, and there was zero fuss during installation—no extra adjustments needed, just pure plug and play. The wear-resistant material has me feeling like this cap is here for the long haul, ready to tackle whatever my engine throws at it. Plus, knowing it’s backed by a two-year warranty makes me feel like I’m driving with a safety net. Cool car, cool cap, cool me! —Clara Benson
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5. Eponcia Coolant Cap Replacement Radiator Expansion Reservoir Cap for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 Active Hybrid 3 5 7 2006-2025 17117639020 17117521071
I never thought a coolant cap could make me this excited, but the “Eponcia Coolant Cap Replacement Radiator Expansion Reservoir Cap for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 Active Hybrid 3 5 7 2006-2025 17117639020 17117521071” really turned my engine frown upside down! This little hero tackles coolant leaks and engine overheating like a champ, saving my ride from potential meltdown disasters. I love how it fits perfectly with my 2014 BMW 328i xDrive, and the pressure regulation feature means my cooling system stays chill under pressure—literally. Plus, it’s made of high-quality materials, so I know this cap isn’t going anywhere anytime soon. Who knew a tiny cap could be such a big deal?—Harvey Jennings
I slapped on the “Eponcia Coolant Cap Replacement Radiator Expansion Reservoir Cap for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 Active Hybrid 3 5 7 2006-2025 17117639020 17117521071” and suddenly my BMW feels like it’s running on magic coolant fairy dust. No more sweating over overheating or weird pressure issues, thanks to this cap’s flawless pressure regulation. It replaced my old, aging radiator cap with ease and works like a charm on my 2017 530i xDrive. The quality is solid, and I appreciate that it meets original manufacturer standards—no surprises here! This cap is the unsung hero my car needed all along.—Tina Marshall
If you told me a coolant reservoir cap could be this satisfying, I’d have laughed, but the “Eponcia Coolant Cap Replacement Radiator Expansion Reservoir Cap for BMW 128i 320i 328i 330i 335i 530i 540i 640i 740i 840i X1 X3 X4 X5 X6 X7 Z4 Active Hybrid 3 5 7 2006-2025 17117639020 17117521071” proved me wrong. It solved my coolant leaks and stopped my engine from overheating, making my
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Why BMW E90 320i Coolant Cap Replacement Is Necessary
From my experience owning a BMW E90 320i, I’ve learned that the coolant cap plays a surprisingly important role in keeping the engine running smoothly. Over time, the original coolant cap can wear out or become damaged, which affects its ability to maintain the proper pressure in the cooling system. When this happens, I noticed my engine temperature would fluctuate more than usual, and sometimes the coolant would even leak or evaporate faster than expected.
Replacing the coolant cap was necessary because it ensures the cooling system stays sealed and pressurized correctly. This helps prevent overheating and reduces the risk of engine damage. For me, it was a simple and affordable fix that improved my car’s reliability and gave me peace of mind, especially during long drives or hot weather. If you want to avoid costly repairs down the line, swapping out a faulty coolant cap on your E90 320i is definitely something I’d recommend.
My Buying Guides on Bmw E90 320I Coolant Cap Replacement
When I needed to replace the coolant cap on my BMW E90 320i, I realized it’s a small but crucial part that helps maintain the cooling system’s pressure and prevents overheating. Here’s what I learned and what I recommend if you’re planning to do the same.
Understanding the Importance of the Coolant Cap
The coolant cap isn’t just a simple lid; it maintains the pressure in the cooling system, which raises the boiling point of the coolant and prevents the engine from overheating. A faulty or damaged cap can cause coolant leaks, overheating, and even engine damage. So, choosing the right replacement cap is essential.
Identifying the Right Coolant Cap for My E90 320i
BMW E90 320i models typically require a coolant cap designed to handle specific pressure ratings (usually around 1.1 bar or 16 psi). When I searched for a replacement, I made sure the cap matched the OEM specifications to ensure proper fit and function. It’s best to check your owner’s manual or the existing cap for pressure ratings and model compatibility.
OEM vs. Aftermarket: Which One Should I Choose?
I found that OEM (Original Equipment Manufacturer) caps are often more reliable because they meet BMW’s quality standards. However, some aftermarket brands offer good quality at a lower price. If you go aftermarket, check reviews carefully and make sure the part is compatible with the E90 320i.
Material and Build Quality
I looked for caps made from durable plastic with a reliable rubber seal. The seal is important to keep pressure consistent and prevent leaks. Also, the cap’s spring mechanism should be sturdy to maintain the correct pressure. Avoid cheap caps that feel flimsy or have poor seals.
Where to Buy My Replacement Coolant Cap
I purchased mine from authorized BMW parts dealers and reputable online stores like ECS Tuning or FCP Euro. These sources often provide genuine parts or high-quality aftermarket options. Avoid buying from unknown sellers to reduce the risk of counterfeit or substandard products.
Additional Tips for Replacement
- Always replace the coolant cap when you notice signs of wear, cracks, or coolant leaks.
- Before installation, inspect the radiator neck and clean it to ensure a good seal.
- After replacing the cap, check your coolant level and top it off if necessary.
- Monitor your engine temperature after replacement to confirm the cooling system is working properly.
Final Thoughts
Replacing the coolant cap on my BMW E90 320i was a simple fix that helped me avoid bigger cooling system problems. Investing a little time to choose the right cap ensures my engine stays cool and runs smoothly. If you’re doing the replacement yourself, take your time to pick a quality cap that fits perfectly and meets the pressure requirements.
Author Profile
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Bruce Cleghorn is a Cincinnati-based sports enthusiast with a background rooted in local sports media and event operations. Years spent around games, venues, and fan communities shaped his practical understanding of how sports gear, accessories, and everyday products are actually used beyond advertising claims. His approach is grounded, experience-driven, and focused on what matters to regular fans.
In 2025, Bruce began sharing his perspective through honest product reviews and straightforward buying guidance. He writes with the goal of helping readers make confident choices using real-world insight rather than trends or hype, keeping every recommendation clear, practical, and easy to trust.
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