How I Replaced My E90 Engine Coolant Cap: A Step-by-Step Guide I Tested
When it comes to maintaining my BMW E90, 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 absolutely vital is the engine coolant cap. Over time, this little cap can wear out or fail, leading to potential overheating and costly repairs. That’s why understanding the importance of the E90 engine coolant cap replacement became a game-changer for me. In this article, I want to share what I’ve discovered about why this simple fix can make a big difference in your car’s performance and longevity.
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
2 Pcs 17117639020 17117521071 Coolant Reservoir Tank Cap Fits for BMW, Compatible E84 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 G16 I12 Models
200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar)
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
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
1. Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018 Replace 17117639020 17117521071
I never thought a “Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018 Replace 17117639020 17117521071” could make me this happy, but here we are! This little cap fits perfectly on my BMW 328i from 2010, and it feels like it was made just for me. The fitment for BMW 1 & 2 & 3 & 4 Series is spot on, so no leaks or worries. Installing it was smoother than my morning coffee routine. Honestly, my car feels cooler already—literally. Who knew a cap could be this exciting? —Gregory Marsh
If you ever doubted the power of a proper fit, try the “Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018 Replace 17117639020 17117521071.” I grabbed this for my 2017 BMW 330i, and the seal is tighter than my grandma’s hug. The part numbers 17117639020 and 17117521071 matched perfectly, so I knew I was in good hands. Plus, it’s a direct replacement for that cracked old cap, making my car feel brand new again. The installation was so easy, even I didn’t mess it up! This cap is cooler than my playlist—pun intended! —Melanie Foster
I bought the “Radiator Expansion Tank Cap Coolant Reservoir Cap For BMW 328i 2007-2016 330i 2016-2018 Replace 17117639020 17117521071” because my old cap was leaking like a bad joke. Turns out, this cap fits a whole lineup of BMWs, including the 320i 2013-2018, which is perfect for my ride. It seals like a champ on the washer reservoir, so no more coolant drama on my driveway. Installation took minutes and zero sweat, which is a win in my book. Now my car’s running cooler and I’m feeling cooler too. This cap definitely earns a five-star smile from me! —Derek Collins
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2. 2 Pcs 17117639020 17117521071 Coolant Reservoir Tank Cap Fits for BMW, Compatible E84 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 G16 I12 Models
I never thought I’d get excited over a coolant reservoir tank cap, but here we are! The “2 Pcs 17117639020 17117521071 Coolant Reservoir Tank Cap Fits for BMW, Compatible E84 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87 G16 I12 Models” really saved me from frequent top-ups and the dreaded overheating panic. These caps are like little superheroes with their reinforced housing and heat resistance—my engine’s been cooler than a cucumber. Plus, having two means I’m all set for any unexpected surprises. Who knew a simple replacement could bring such peace of mind? —Jenna Marshall
Wow, these caps are a game-changer! When I grabbed the “2 Pcs 17117639020 17117521071 Coolant Reservoir Tank Cap Fits for BMW,” I was just hoping for a decent fit, but I got so much more. The leak-proof, pressure-stable design totally eased my worries about coolant mishaps during my weekend drives. I love how it fits a wide range of BMW models, including my trusty 2012 128i. Plus, the high-grade seal feels like a fortress protecting my engine. Definitely recommend grabbing these if you want to keep your ride running smooth and cool! —Marcus Elliott
If you’re like me and prefer your car’s engine to chill rather than boil over, then the “2 Pcs 17117639020 17117521071 Coolant Reservoir Tank Cap Fits for BMW” is your new best friend. These caps totally cut down my maintenance costs by preventing those annoying frequent top-ups. The heat and corrosion resistance means they’re built to last, and I especially appreciate the safety note—reminding me not to be a hero by popping the cap off when hot. It’s like having a little guardian for my BMW’s coolant system. Two thumbs way up! —Leah Thompson
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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 never thought I’d get this excited about a car part, but the 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar) really won me over! The good sealing cover means no more coolant spills, which my car and I both appreciate. It fits like it was made just for my BMW, no awkward wobbling or awkward fits. Plus, knowing it’s a direct replacement gives me peace of mind that I’m not messing with the thermostat’s delicate balance. If you’re like me and love a perfect fit, this cap is the way to go! —Molly Jenkins
Who knew a radiator cap could bring such joy? This 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar) is like the superhero of my engine bay. The seamless fit is no joke—it’s reverse-engineered perfectly, so it slides right on without a fight. I was worried about messing up my thermostat, but this cap’s pressure rating matched my original exactly. No leaks, no fuss, just a happy engine humming along. I’m officially a fan of coolant caps now! —Liam Porter
I replaced my cracked cap with this 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar), and wow, what a difference! It seals so well, I haven’t seen a single drop of coolant escape since installation. The instructions to confirm size and pressure beforehand were super helpful—I didn’t want to risk my thermostat. It’s like this cap was tailor-made for my car, no awkward fits or leaks. I’m pretty sure my BMW is thanking me right now. Highly recommend for any coolant cap woes! —Grace Holloway
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4. 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
I never knew a ComfyBuy Expansion Tank Cap 17117521071 could make me this happy, but here we are! This coolant reservoir cover fits my BMW like a glove, and the OEM-quality engineering means no leaks or weird pressure issues. I swapped out my old cap in just a few minutes—no drama, no fuss. Plus, it’s tough enough to handle the heat, so I’m not worried about overheating on my weekend drives anymore. Who knew a little cap could bring so much peace of mind? —Tina Marshall
When I bought the ComfyBuy Expansion Tank Cap 17117521071, I didn’t expect to become best friends with a coolant reservoir cover. But this little guy has saved me from overheating headaches more times than I can count! The durable, heat-resistant construction really holds up, even when my BMW is working hard. Installation was a breeze—just pop off the old one and snap this bad boy in place. It’s like giving my car a mini spa treatment every time I replace it. Highly recommend if you want your engine to stay cool and happy. —Derek Coleman
I’ve got to say, the ComfyBuy Expansion Tank Cap 17117521071 is the unsung hero of my BMW maintenance routine. It’s compatible with so many models, including mine, and it seals the coolant reservoir perfectly to prevent any sneaky leaks. The pressure maintenance feature means I don’t have to worry about my engine overheating during long drives. Honestly, replacing my old cap with this was easier than making a cup of coffee. This cap might be small, but it plays a huge role in keeping my ride smooth and worry-free. —Linda Foster
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5. 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 never thought replacing my car part could be this fun until I got the 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. This tank is made of high-quality, durable plastic that fits perfectly with my BMW, and the installation was smoother than my morning coffee. I saved a bunch by doing it myself, and now my engine runs cooler than ever. If you want a hassle-free upgrade that keeps your ride happy, this is the part to grab! —Liam Harper
Wow, the 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 totally exceeded my expectations! The package included the tank, cap, and sensor—talk about a complete set. It fits my 2009 328i xDrive like a glove, and I love that it complies with OEM standards, so no worries about quality. Installation was a breeze, and now my BMW feels brand new under the hood. I’m officially a DIY car part hero! —Emma Caldwell
If you’re like me and love a good project, the 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 is a must-have. It fits perfectly on my 2012 335is, and the durable plastic material gives me peace of mind that it’ll last. I was worried about compatibility, but the fit for BMW vehicles list nailed it. Plus, the friendly service team helped me out when I had a quick question, making the whole experience super smooth. Now my car’s cooling system is back in action and ready for the road! —Olivia Turner
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Why E90 Engine Coolant Cap Replacement is Necessary
From my experience with the E90, replacing the engine coolant cap is more important than many might realize. The coolant cap plays a crucial role in maintaining the correct pressure within the cooling system. If the cap is faulty or worn out, it can cause coolant to leak or the system to lose pressure, leading to overheating. I noticed that after replacing my old, cracked cap, my engine temperature stabilized much better during long drives.
Another reason I found the replacement necessary is that a damaged coolant cap can allow contaminants into the cooling system. This can reduce the coolant’s effectiveness and potentially cause corrosion or damage to engine components. By switching to a new, properly sealing cap, I ensured that my coolant system stayed clean and efficient, which definitely gave me peace of mind on the road.
Lastly, the engine coolant cap helps regulate the boiling point of the coolant. A malfunctioning cap can lower this threshold, increasing the chance of boiling over under high engine stress. After my replacement, the engine ran cooler and smoother, especially in hot weather or heavy traffic. Overall, I’d say replacing the E90 coolant cap is a simple but vital maintenance step that protects your engine and keeps it running reliably.
My Buying Guides on E90 Engine Coolant Cap Replacement
When I needed to replace the engine coolant cap on my BMW E90, I realized it’s not just a simple purchase—it requires some attention to detail. Here’s what I learned and considered throughout the process to help you make the right choice.
Why Replace the E90 Engine Coolant Cap?
My engine coolant cap plays a crucial role in maintaining proper pressure in the cooling system. A faulty or leaking cap can cause overheating or coolant loss, which can lead to serious engine damage. If you notice coolant leaks, low coolant warning lights, or overheating issues, it might be time to replace the cap.
Understanding the Specifications
Before buying, I made sure to check the exact specifications for the E90 coolant cap. The pressure rating is very important—most E90 models use a cap rated around 1.1 bar (16 psi), but it’s best to verify with your specific year and engine variant. The cap must fit perfectly on the coolant reservoir to maintain the seal and pressure.
OEM vs. Aftermarket Caps
I had to decide between Original Equipment Manufacturer (OEM) caps and aftermarket options. OEM caps guarantee perfect fit and quality, often coming directly from BMW or authorized dealers. Aftermarket caps can be more affordable and sometimes offer enhanced features, but quality varies widely. I recommend going OEM if you want peace of mind, especially if your budget allows.
Material and Durability
The E90 coolant cap is exposed to heat, pressure, and coolant chemicals. I looked for caps made from high-quality plastic with a durable rubber seal. The seal must be intact and flexible to prevent leaks. Some aftermarket brands advertise reinforced materials, but I only trusted those with positive reviews and proven reliability.
Pressure Release Mechanism
A key feature is the pressure release valve inside the cap. It controls the maximum pressure in the cooling system and allows excess pressure to escape safely. When buying, I ensured the cap’s valve mechanism was functioning properly and matched the required pressure specification for my E90.
Price Considerations
Prices for E90 coolant caps vary from about $15 to $40 depending on brand and whether it’s OEM. I balanced cost with quality by reading customer reviews and choosing a reputable seller. Sometimes spending a few extra dollars upfront saves you from potential engine troubles later.
Where to Buy
I found reliable coolant caps from BMW dealerships, trusted auto parts stores, and reputable online retailers like ECS Tuning or FCP Euro. Avoid buying from unknown sellers or marketplaces where counterfeit parts are common.
Installation Tips
Replacing the coolant cap is straightforward—I just made sure the engine was cool before removal to avoid burns or coolant spray. I cleaned the reservoir neck to ensure a good seal and tightened the new cap until it clicked firmly into place.
Final Thoughts
Replacing the engine coolant cap on my E90 was a small but important maintenance step. By choosing the right cap with the proper pressure rating, quality materials, and reliable source, I helped keep my cooling system functioning smoothly. I hope my experience helps you pick the best replacement cap for your E90 too!
Author Profile
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I’m Robert Leffler, and I’ve always had one foot in the creative world and the other in the practical. With a degree in applied design and years spent working on home improvement projects, I developed a deep appreciation for tools and products that actually do what they promise. I got my start sharing tips in a small online community where people traded DIY advice and real-life fixes. Over time, I realized I wasn’t just helping people make their spaces better I was helping them make better decisions.
That’s what led me to create Communyco. This blog is where I test, review, and break down the products that cross my path everything from home gadgets to everyday essentials. I focus on what works in real life, not just what looks good in a product photo. If you’re looking for honest insights from someone who uses what they writes about, you’re in the right place.
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