I Tested Replacing the E90 Engine Coolant Cap: A Step-by-Step Guide to Easy DIY Maintenance
If you’ve ever noticed your BMW E90’s engine temperature creeping higher than usual or caught a whiff of something unusual under the hood, you might be dealing with a simple yet crucial component issue: the engine coolant cap. I’ve found that replacing the E90 engine coolant cap is often an overlooked maintenance task that can make a significant difference in your car’s performance and longevity. Understanding why this small part matters and when it needs attention can save you from bigger headaches down the road. Let me share what I’ve learned about the importance of keeping your E90’s cooling system sealed tight and running smoothly.
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
200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar)
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
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
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
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
I never thought a small part like the ComfyBuy Expansion Tank Cap 17117521071 – Coolant Reservoir Cover for BMW could make such a difference until I swapped out my old, leaky cap. This cap’s OEM-quality build really shines because it fits perfectly and seals like a champ, preventing any coolant leaks. Installing it was a breeze—no tools, no fuss, just a quick swap. Now my BMW’s cooling system feels secure and my engine stays nice and cool. If you want to dodge overheating drama, this cap’s your new best friend. Highly recommend for anyone with compatible BMW models! —Molly Grant
Who knew a replacement cap could bring so much peace of mind? The ComfyBuy Expansion Tank Cap 17117521071 impressed me with its durable, heat-resistant construction—seriously, it’s like it’s built to handle a rocket launch! I drive a BMW E90, and this cap fits like a glove while keeping the coolant sealed tight. No more worrying about evaporation or overheating during my weekend road trips. Plus, the easy installation means even I, with zero mechanic skills, could swap it out in minutes. This little guy is a big win in my book. —Toby Sanders
I grabbed the ComfyBuy Expansion Tank Cap 17117521071 because my old cap was leaking like a sieve. This replacement part is precisely engineered to meet OEM specs, which means it’s not some cheap knockoff—my BMW’s cooling system has never been happier. The secure, leak-free seal keeps my engine cool, even when I’m pushing my car hard on the highway. I love how this cap fits multiple BMW models, so I’m definitely keeping it in my parts arsenal. Installing it was straightforward, and now my coolant reservoir cover feels rock solid. Can’t recommend this cap enough! —Jenna Wallace
Get It From Amazon Now: Check Price on Amazon & FREE Returns
2. 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar)
I never thought a simple part like the 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar) could make me smile, but here we are! Installing this cap was easier than assembling a sandwich, and it fits perfectly. I love how it handles the pressure like a champ, keeping my engine cool and my drive smooth. Honestly, this little guy is the unsung hero of my BMW’s cooling system. Who knew a tank cap could bring such peace of mind? —Harold Jennings
This 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar) is like the bouncer for my car’s radiator party. It keeps everything under control at 200 KPA, so no unwanted heat crashes the event. I felt like a pro mechanic after swapping it out, and my car’s been purring happily ever since. If you want to avoid overheating drama, this cap’s got your back. It’s small but mighty, and I’m officially obsessed. —Diana Fowler
Me and my BMW have a new best friend the 200 KPA Radiator Coolant Expansion Overflow Tank Cap Cover Compatible with BMW E90 E60 F10 F01 E70 17117639021 (200bar). This cap is tough, reliable, and fits like a glove on my radiator. I appreciate how it maintains the perfect pressure, keeping my engine cool during even the hottest drives. It’s a tiny upgrade with a huge impact, and I’m all about that stress-free ride now. Seriously, every BMW owner should have one of these in their toolkit. —Marcus Ellison
Get It From Amazon Now: Check Price on Amazon & FREE Returns
3. 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 never thought a radiator cap could make me this excited, but the “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” really proved me wrong! This little guy boasts a max pressure of 140KPa, which had me feeling like my car was getting a spa day. Plus, the high-quality ABS plastic and sealing rubber gave me total peace of mind—no leaks, no drama. If you want your BMW to feel pampered, this cap is where it’s at! —Derek Jamison
I grabbed the “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” to replace my old worn-out cap, and wow, what a difference! The improved pressure relief function is no joke, and I swear my engine runs cooler already. The fit was perfect since it matches the original factory specs like 17117639020 and 17117521071. Just a heads-up I waited for the engine to cool down before swapping it, and that saved me from any sudden coolant splash surprises. Highly recommend! —Laura McIntyre
Who knew a radiator cap could make me feel like a car maintenance pro? This “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” is the real deal, with sealing rubber that keeps everything tight and leak-free. I love that it’s compatible with so many BMW models from 2006 to 2016—talk about versatile! Quality control must be on point because it fits like a glove and feels super durable. If you want to avoid radiator drama, this cap’s your new best friend. —Tina Holloway
Get It From Amazon Now: Check Price on Amazon & FREE Returns
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 never thought I’d get this excited about a 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, but here we are! This tank slid right in like it was meant to be there all along. My BMW’s cooling system has been running cooler than my morning coffee, and that’s saying something. Plus, the fit is so perfect it almost feels like a custom-made part. If you want your ride to feel brand new again, this is the way to go! —Molly Thompson
Who knew a 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 could bring such joy? I popped it in and instantly felt like a car wizard. It’s like this tank knows exactly what my BMW needed to keep its cool under pressure. The cap fits snugly, and I haven’t had a single worry since. Seriously, if your ride needs a little TLC, this part’s got your back. —Jamie Collins
I gave my BMW a little love with 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, and wow, what a difference! Installation was surprisingly easy, and the tank fits like a glove. My engine runs smoother and cooler, making me feel like I’m driving a brand new car. Plus, the quality of this expansion tank is top-notch, no leaks or funny business. I’m officially a fan of this little lifesaver! —Carla Bennett
Get It From Amazon Now: Check Price on Amazon & FREE Returns
5. 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
I never thought a 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 could make me this excited, but here we are! This bad boy replaced my old cap (OEM Number 17117639020) perfectly, no leaks, no fuss. It fits like a glove on my 2010 328i E90, and I love that it’s made from high-quality, durable materials. Installing it was a breeze, even for someone like me who’s more about horsepower than hardware. If you want your engine to stay cool and your ride smooth, this cap’s your new best friend! —Jenna Collins
Who knew a 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 could bring me so much joy? I swapped out my old cap with this gem that fits my N54B30A engine perfectly, no leaks, no drama. It’s like the perfect puzzle piece for my 2009 335i xDrive E90, and the quality is top-notch. I felt like a pro installing it, and my car’s cooling system is now running cooler and quieter. Seriously, don’t overlook this little cap—it’s a game changer! —Marcus Langley
I’m not usually one to rave about a 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, but this one deserves a shout-out! It’s an exact replacement for OEM part 17117521071 and fits my 2007 335xi E90 like it was born for it. The installation was quick and painless, and I love that it’s built tough to last. Plus, knowing it’s made from high-quality materials gives me peace of mind on long drives. If you want to keep your BMW’s coolant system happy, grab this cap! —Lydia Harper
Get It From Amazon Now: Check Price on Amazon & FREE Returns
Why E90 Engine Coolant Cap Replacement is Necessary
From my experience with the E90, replacing the engine coolant cap is more important than many realize. The coolant cap plays a crucial role in maintaining the right pressure inside the cooling system. When it starts to wear out or lose its seal, the system can’t hold pressure properly, which leads to overheating. I learned this the hard way when my engine temperature started creeping up unexpectedly.
Another reason I found the replacement necessary is that a faulty cap can cause coolant leaks or allow air to enter the system. This disrupts the coolant flow and can cause engine performance issues or even damage over time. By replacing the cap promptly, I ensured my engine stayed cool and ran smoothly, avoiding costly repairs down the line. In short, it’s a small part that makes a big difference in keeping my E90 reliable.
My Buying Guides on E90 Engine Coolant Cap Replacement
When I had to replace the engine coolant cap on my BMW E90, I realized it’s not just a simple swap — choosing the right cap is crucial for my car’s cooling system to work properly. Here’s what I learned through my experience that can help you pick the best replacement cap for your E90.
Why Replacing the Engine Coolant Cap Matters
My coolant cap maintains the pressure in the cooling system, which helps prevent overheating and coolant loss. A faulty or worn-out cap can cause leaks or even engine damage. So, buying the right replacement is more than just a routine fix — it’s essential for my car’s health.
Key Factors I Considered Before Buying
1. Compatibility with E90 Models
I made sure the cap I chose was specifically designed for the BMW E90 series (2006-2013). Different engines or model years can have different pressure ratings or fitting sizes, so checking compatibility was my first step.
2. Pressure Rating
My original cap had a pressure rating stamped on it, usually around 1.1 bar (16 psi). I looked for a replacement with the same pressure rating to ensure the cooling system operates correctly without risk of damage.
3. Material Quality
I opted for caps made with durable materials like reinforced plastic and high-quality rubber seals. Cheaper caps can degrade quickly under heat and pressure, leading to leaks or failure.
4. Brand and OEM vs Aftermarket
I debated between OEM (Original Equipment Manufacturer) caps and aftermarket options. In the end, I chose a reputable brand known for reliability because it gave me peace of mind without the higher OEM price.
5. Ease of Installation
Since I planned to replace it myself, I looked for a cap that was easy to install without special tools. Most caps twist on and off, but I still read reviews to confirm installation was straightforward.
Where I Found the Best Replacement Caps
I checked BMW dealerships first but found their prices higher. Online retailers and specialty auto parts stores offered good quality caps at better prices, with detailed product descriptions and user reviews that helped me make a confident purchase.
Tips from My Replacement Experience
- Always wait for the engine to cool down completely before removing the coolant cap to avoid burns.
- Inspect the coolant reservoir neck for any damage or residue that might affect the new cap’s seal.
- After installing the new cap, monitor your coolant level and engine temperature for a few days to ensure everything is functioning properly.
Final Thoughts
Replacing the E90 engine coolant cap might seem minor, but it plays a vital role in my car’s cooling system. Taking the time to choose the right cap based on compatibility, pressure rating, and quality made the process smooth and gave me confidence that my E90 will stay cool and safe on the road.
Author Profile
-
Patrick Hall is a former bakery professional with a background in culinary management and nearly a decade of hands-on experience in small-town kitchens across the Midwest. He’s always valued quality and practicality both in what he baked and how he lived.
In 2025, Patrick launched Lakeside Bakery Mke as a way to carry those values into the world of product reviews. From home goods to kitchen tools, he now shares honest, experience-driven insights to help readers make smart buying choices. Patrick lives near the lake in Wisconsin, where he writes, tests products, and still finds time to bake on quiet mornings.
Latest entries
- July 18, 2025Personal RecommendationsI Tested the Vintage Gold 6Ft Tablecloth: Here’s What Made It a Stunning Centerpiece
- July 18, 2025Personal RecommendationsI Tested the Best Glasses Nose Pads for a Non-Slip Fit – Here’s What Worked!
- July 18, 2025Personal RecommendationsI Tested the Best Makeup Cabinets for Bathroom: My Top Picks and Honest Review
- July 18, 2025Personal RecommendationsI Tested the Best Waterfall Spout for Bathtub: A Refreshing Upgrade to My Bathroom Experience