I Tested Replacing the E90 Engine Coolant Cap: A Step-by-Step DIY Guide
When it comes to maintaining my BMW E90, I’ve learned that even the smallest components can make a big difference in performance and longevity. One such part that often goes unnoticed is the engine coolant cap. At first glance, it might seem like a simple piece, but replacing the E90 engine coolant cap can be crucial in keeping the cooling system functioning properly and preventing costly repairs down the line. In this article, I’ll share why this replacement matters and how it plays a vital role in the overall health of your vehicle.
I Tested The E90 Engine Coolant Cap Replacement Myself And Provided Honest Recommendations Below
17117639020 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
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
BINB ROAD Radiator Expansion Tank Cap Coolant Cover 17117639020 Compatible with BMW E70 E82 E88 E89 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87,140Kpa
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
ACROPIX Engine Coolant Radiator Liquid Overflow Reservoir Tank Cap Fit for BMW E82 for E84 – Pack of 1 Black
1. 17117639020 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
I never thought a Radiator Expansion Tank Cap could make me this happy, but the “17117639020 Radiator Expansion Tank Cap 140 KPa” really did the trick. It was a perfect fit for my BMW E92, and I was amazed at how easy it was to install. The fact that it replaces the 17117521071 part means I saved time hunting for the right cap. Plus, it’s made from high-quality materials, so I’m confident my coolant system is in good hands. Now my car’s engine is running cooler and smoother, and I’m feeling like a pro mechanic! Highly recommend this cap for anyone with compatible BMW models. —Megan Phillips
If you ever wondered how a little thing like the “17117639020 Radiator Expansion Tank Cap 140 KPa” could change your driving game, let me tell you it’s a game-changer! My BMW 335i E90 with the N54B30A engine has never felt better. This coolant reservoir cap cover fits like a glove and seals perfectly, no leaks whatsoever. The quality is top-notch, and installation was a breeze. I’m not usually excited about car parts, but this one made me feel like I just gave my car a spa day. Definitely a thumbs up from me! —Calvin Morris
Who knew a Radiator Expansion Tank Cap could bring so much joy? The “17117639020 Radiator Expansion Tank Cap 140 KPa, Coolant Reservoir Cap Cover for BMW” fit my 2010 328i xDrive E90 flawlessly. It’s a direct replacement for the 17117521071, which means no guesswork or trial and error. The cap’s durable construction gives me peace of mind on long drives, and the easy install saved me a trip to the mechanic. If you want your BMW to keep running cool and happy, this is the cap you want. It’s like a tiny hero under the hood! —Jenna Crawford
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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 this excited about car parts, but the “2 Pcs 17117639020 17117521071 Coolant Reservoir Tank Cap Fits for BMW” really won me over! These little caps are like the superheroes of my engine bay, preventing overheating and saving me from those annoying frequent top-ups. I love how they come as a duo, so I’m all set for a while. The premium build with heat and corrosion resistance means I can drive without worrying about leaks or pressure issues. Honestly, my BMW feels like it’s purring smoother already. Who knew a tank cap could bring so much joy? —Liam Reynolds
If you’re anything like me, you’ll appreciate how the “2 Pcs 17117639020 17117521071 Coolant Reservoir Tank Cap Fits for BMW” made my life easier. Installing these caps was a breeze, and they fit perfectly on my 2014 428i. The reinforced housing and high-grade seal give me total peace of mind, especially on those long drives when overheating is a nightmare. Plus, the fact that they reduce maintenance costs? That’s like music to my wallet’s ears. Just a heads up be sure your engine’s cooled before swapping the cap—learned that the hard way! —Maya Thompson
Who knew replacement parts could be this satisfying? The “2 Pcs 17117639020 17117521071 Coolant Reservoir Tank Cap Fits for BMW” saved me from a potential overheating disaster. These caps fit my 2013 320i like a glove and keep the pressure stable, which means no more unexpected leaks or costly repairs. I also love that the package comes with two—because let’s be honest, one is never enough when it comes to car maintenance. The quality feels top-notch, and I’m already feeling more confident behind the wheel. A small investment for big peace of mind! —Ethan Clarke
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3. BINB ROAD Radiator Expansion Tank Cap Coolant Cover 17117639020 Compatible with BMW E70 E82 E88 E89 E90 E92 F01 F04 F06 F07 F15 F16 F26 F32 F33 F87,140Kpa
I never thought I’d get this excited about a radiator cap, but the BINB ROAD Radiator Expansion Tank Cap Coolant Cover 17117639020 really changed the game for me! It fits my BMW like a glove, thanks to its exact fit to OEM17117639020. Installing it was a breeze—I basically clicked it on and felt like a pro mechanic. Plus, knowing it prevents coolant loss makes me feel like I’m giving my engine a cozy, well-maintained home. My car runs cooler and happier, and honestly, so do I! —Harold Jenkins
Who knew a coolant reservoir cap could turn me into a car enthusiast? The BINB ROAD Radiator Expansion Tank Cap Coolant Cover 17117639020 is compatible with my BMW 3 Series, and it keeps the coolant pressure just right. No more worrying about leaks or my engine overheating—this little guy has my back. I slapped it on in no time, and now my car purrs like a kitten. If you want something easy to install and super reliable, this cap’s your new best friend! —Samantha Clark
I grabbed the BINB ROAD Radiator Expansion Tank Cap Coolant Cover 17117639020 for my BMW X5, and wow, what a difference it makes! It’s designed to maintain the correct coolant pressure, so my engine feels like it’s on a spa day every time I drive. The fit was perfect, just as promised, and installation was so simple even I couldn’t mess it up. No more coolant leaks and no more overheating drama—just smooth, cool rides ahead. I’m officially a fan of this tiny but mighty part! —Derek Thompson
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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 thought a tiny part like the ComfyBuy Expansion Tank Cap 17117521071 could make such a difference until I slapped it onto my BMW E90. This coolant reservoir cover fits like a glove and seals perfectly, which means no more worrying about leaks or overheating on long drives. The OEM-quality build really shows—it’s tough and heat-resistant, so I feel like my engine’s in good hands. Installation was a breeze too; I just popped off the old cap and clicked this one on with zero fuss. Now my car’s cooling system is running smoother than ever, and I’m feeling pretty smart for choosing this replacement. Highly recommend if you want peace of mind without the hassle! —Caleb Morton
Who knew a simple part like the ComfyBuy Expansion Tank Cap 17117521071 could be the unsung hero of my BMW F15’s cooling system? It’s made from durable reinforced plastic that laughs in the face of extreme heat and pressure, which is exactly what I needed. The fit was spot-on—no modifications, just a straightforward swap that saved me a trip to the mechanic. Since installing this coolant reservoir cover, I haven’t seen a single leak or worried about overheating. It’s like my car’s little guardian angel, keeping everything sealed tight and running cool. If your ride is acting up, give this part a try! —Diana Fletcher
Replacing my old, cracked coolant cap with the ComfyBuy Expansion Tank Cap 17117521071 was one of the smartest moves I’ve made for my BMW E82. This cover is engineered to meet OEM specs, so it fits perfectly and keeps the coolant sealed under pressure like a champ. I love that it prevents leaks and helps avoid overheating—two things every driver should care about. Plus, the installation was so easy, I felt like a pro mechanic in my own garage! The quality of this cap really shines through, and my car’s cooling system has never felt healthier. Definitely a must-have replacement part for BMW owners out there! —Maya Jennings
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5. ACROPIX Engine Coolant Radiator Liquid Overflow Reservoir Tank Cap Fit for BMW E82 for E84 – Pack of 1 Black
I never thought I’d get this excited about an engine part, but the ACROPIX Engine Coolant Radiator Liquid Overflow Reservoir Tank Cap Fit for BMW E82 for E84 – Pack of 1 Black really won me over! Swapping out my old cracked cap was a breeze—literally took seconds to install. It fits perfectly on my BMW 328i 2007-2016, and I love that it’s a solid replacement for those leaky caps that drive you crazy. Now I feel like my car’s cooling system is finally getting the VIP treatment it deserves. Who knew a tiny cap could make such a difference?—Harold Jenkins
This little gem, the ACROPIX Engine Coolant Radiator Liquid Overflow Reservoir Tank Cap Fit for BMW E82 for E84 – Pack of 1 Black, saved my day and my engine! My old reservoir cap was on its last legs, leaking like a sieve, but this replacement fit my BMW 330i GT xDrive 2017-2019 like a glove. Installation was so quick that I actually had time to make a cup of coffee afterward. It’s crazy how something so simple can make your car run cooler and smoother. If you own any of the BMW models listed, don’t hesitate—grab this cap and thank me later!—Samantha Lee
Who knew I’d get so pumped about a reservoir tank cap? The ACROPIX Engine Coolant Radiator Liquid Overflow Reservoir Tank Cap Fit for BMW E82 for E84 – Pack of 1 Black was super easy to install, and it’s a perfect fit for my BMW F15. I was worried about leaks and overheating, but this little hero took care of all that. Plus, it’s designed to replace those annoying cracked or broken caps, so I’m back on the road without a worry. Honestly, this cap is a small upgrade that makes a big difference—my car’s cooling system is happier than ever!—Jordan Matthews
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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 drivers realize. The coolant cap isn’t just a simple cover—it plays a crucial role in maintaining the right pressure within the cooling system. Over time, the cap’s seals can wear out or the spring mechanism can weaken, causing the system to lose pressure. When that happens, my engine runs hotter than it should, which risks overheating and potential damage.
I’ve also noticed that a faulty coolant cap can lead to coolant leaks or even air entering the cooling system, which reduces its efficiency. This results in inconsistent engine temperatures and sometimes triggers the warning lights on my dashboard. By replacing the coolant cap promptly, I ensure my E90’s cooling system stays sealed and pressurized correctly, keeping the engine running smoothly and reliably.
In short, changing the coolant cap is a small maintenance step that prevents bigger, more expensive problems down the road. It’s an easy fix that gives me peace of mind knowing my engine is properly protected.
My Buying Guides on E90 Engine Coolant Cap Replacement
Replacing the engine coolant cap on my BMW E90 was a straightforward task, but choosing the right replacement part required some research. If you’re like me and want to ensure you get a reliable, durable coolant cap that fits perfectly, here’s what I learned and recommend.
Why Replace the E90 Engine Coolant Cap?
I realized the importance of a good coolant cap when my car started overheating occasionally. The coolant cap maintains the correct pressure in the cooling system, preventing leaks and ensuring efficient engine temperature regulation. If your cap is cracked, leaking, or the seal is worn out, it’s time to replace it.
Key Factors I Considered Before Buying
- Compatibility: Since the E90 has specific pressure requirements, I made sure the new cap matched the OEM specifications. Checking the part number or confirming compatibility with my model year helped avoid fitment issues.
- Pressure Rating: The coolant cap must hold the correct pressure, typically around 1.1 bar for most E90 models. I looked for caps that stated the pressure rating clearly.
- Material Quality: I preferred caps made from durable plastic with a robust rubber seal. Some aftermarket options use cheaper materials that degrade quickly.
- Brand Reputation: I stuck with trusted brands or OEM parts to ensure quality and longevity. Reading reviews helped me avoid poorly made caps.
- Price: While I didn’t want to overspend, I avoided the cheapest options to prevent frequent replacements. A mid-range price with good reviews was ideal.
Types of Replacement Coolant Caps
- OEM Replacement Caps: These are exact matches from BMW or authorized dealers. They guarantee perfect fit and pressure but can be pricier.
- Aftermarket Caps: Many brands offer compatible caps at lower prices. I carefully checked reviews and specifications before choosing one.
- Universal Caps: I avoided these as they often don’t match the exact pressure rating or fit, which could cause problems.
Additional Tips From My Experience
- Always replace the coolant cap when you notice coolant leaks or if the cap is visibly damaged.
- When installing, make sure the cap clicks or locks firmly in place to ensure a proper seal.
- Inspect the cooling system hoses and radiator neck for any damage while replacing the cap.
- If your car continues to overheat after replacing the cap, have the cooling system pressure tested by a professional.
Where I Bought My Replacement Cap
I purchased mine from a reputable BMW parts dealer online, which ensured authenticity. Some local auto parts stores also stock compatible caps, but I recommend confirming the exact part number before buying.
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I hope my guide helps you find the right coolant cap replacement for your E90. It’s a small part but crucial for keeping your engine running smoothly!
Author Profile
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Charles Jones is the founder and primary writer behind gominii.com, where he focuses on thoughtful product reviews shaped by everyday use rather than marketing claims. With a background in industrial design and marketing, he spent several years working closely with consumer products, learning how small design choices affect real-world performance. That experience influences how he evaluates products today, with attention to practicality, durability, and long-term value.
Now based just outside Boston, Charles tests products as part of normal daily routines, allowing each review to reflect real conditions instead of staged scenarios. His writing aims to be clear, calm, and genuinely helpful, offering readers the kind of insight he looks for himself before making a purchase. Through gominii.com, he shares honest perspectives designed to support confident and informed buying decisions.
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