Welcome guest, Sign in or Register

2016+ Honda Civic & Acura Integra Coolant Expansion Tank Upgrade

2016+ Honda Civic & Acura Integra Coolant Expansion Tank Upgrade

10th Gen 1.5T owners select Non-Si or Si option. Type R or Type S owners select the correct year to ensure proper fitment
Have questions about this product or anything else 27WON related?

TEXT US! 571-271-0271
Add to wish list


Now look, we all know by now that Honda didn’t prioritize looks much underneath the engine bay of the Civic X. Just look around and you can find cost cutting measures everywhere and the stock coolant expansion tank in the upper left corner is no exception. This did not change with the launch of the latest FL5 Type R and DE5 Type S either. Same plastic tank on both!

It just screams, BASIC! Plus, it’s known to develop cracks over time and leak. Ouch!

So, what are we going to do about that? Well, how about design a sleek looking upgraded coolant tank that holds the pressure. It is made of strong aluminum, fully seam welded to prevent leaks, has a level check dipstick that’s an accomplishment all in and of itself. We round out this kit with proper fitments for Civic X 1.5T Non-Si, Si, as well as the 2.0T Type R FK8. We were able to pick up FL5/DE5 applications too. Looks like you just found your next mod fam!

dare to redefine sub headline banner

27won redefine design subheadline
Coolant tank for FL5 Civic

What’s an egg-shell color, gets dirty quickly, sticks outs amongst all the metal underneath the hood of your 10th Gen Civic? If you guessed your stock plastic expansion tank aka coolant tank, then you guessed right. Chuck that boring plastic out the window and get down with our fully seam welded aluminum expansion tank. We’ve hit the looks out of the park with this one. Just look at those welds and smooth high temp paint finish.

And pay careful attention to the filler neck and how it’s welded from the inside out! Why? Because it’s one less weld to see and gives us a much cleaner design. That’s something you’ll only find on this Coolant Tank.

27won redefine design subheadline
Coolant tank with black powdercoat installed in Honda Civic Type R

The coolant expansion tank is a simple device with a couple of functions on your late model Civic or Integra. It holds extra coolant, it’s a spot to refill and replace lost coolant, it’s the highest point in the system so will be used to bleed the system If needed, and most importantly it pressurizes the coolant/water mixture to raise its boiling point. Again, a simple, but important part of the cooling system on all 1.5T and 2.0T applications.

If it develops a crack however, it can’t hold the pressure and that’s what’s been happening with the stock coolant tanks on these cars for a while. The stock plastic dulls, gets yellow and brittle over time leading to cracks and worse! Part of the solution here involved switching to aluminum construction for strength. No more brittle plastic. We’ve rated these tanks to hold over 30PSI, well above OE cap pressure (CTR) of 1.3 BAR. That’s above what your cooling system will see at any given time so you know these are built to perform.

27won redefine design subheadline
Shown installed on Civic Si Sedan using the supplied hardware

As with everything we put out, we want a simple yet profound upgrade without the fuss. Never visit another hardware store in the middle of an install ever again. We’ll include everything you need to get your upgraded coolant tank installed in about an hour and be the show-off at your next Honda meet.

27won redefine design subheadline
An orange dipstick shown to check coolant levels

Ok, you’re probably thinking to yourself, how are you going to check the level of the coolant? A sight glass or plastic tube? Nope, that’s old school and boring. Plus, they also leak over time and discolor so why would be introduce another version of issue we are solving in the first place?

Enter the dipstick. Yes, they’ve been used for a long time on cars for checking things like oil. But, why not coolant? So, we designed this sick looking dipstick that allows for a quick check of the coolant (follow OE instructions for removal of coolant cap). Simply unscrew the cap, dip the dipstick down to the neck of the coolant tank, and see if there is coolant on the threads. Top off as needed to get coolant to at least half way (7 threads). When you’re done, simply hang the dipstick on your key chain, put in the glovebox, or stash it somewhere creative with the included holster.

27won redefine design subheadline
Multiple fitment options shown

Our modular design allows for fitment across multiple models by selecting the appropriate NPT fittings specifically for your trim. No need to retrofit or modify. Our coolant tank will work right out of the box.

learn more sub headline banner

Read about our entire design process for this coolant tank below!

advisory subheadline
  • Follow Owner’s Manual for removal of the coolant cap. We recommend checking your coolant level at each oil change
  • The supplied dipstick is used to check the coolant level. The minimum fill level is to the first thread of the dipstick. Full is considered at least 7 threads from the bottom of the dipstick. Don't fill coolant past the threads
  • Fitment for 2016-2021 2.0L Naturally Aspirated Civics is not confirmed at this time
  • This product does not fit 2022+ Civic or Integra except those equipped with the 2.0T engine

27won service and support subheadline


I really appreciate 27won for their attention to detail and dedication to making upgrades that are enjoyable to install (and just have because of craftsmanship) alongside the performance benefits. I feel like that's something that's lost in other aftermarket companies that just bang out items for sales.

This coolant tank is a great example of that philosophy. Yes, this will take longer to install than a coolant reservoir on a 92 civic, but doesn't everything on an FK8? The tank is solid; very nice welds and strong mounting points. The directions are as detailed as they always are for 27won. The addition of the coolant dipstick holder was pretty sweet too. I mounted mine in the glovebox and it's always a nice little reminder of that upgrade whenever I'm looking for a pen or getting out my Flashpro cable.

My Chasing J's Titanium cap swapped onto the 27won reservoir just fine and I have not had any issues with any leaks or anything since installing it. Granted it's only been under 500 miles, but if there was an issue, it would have showed up by now.

Thanks for another great product that I get to use on my FK8!
Write a review


2016 - 2021 Honda Civic Si and Non-Si 1.5T (Sedan, Coupe, Hatchback)
2017 - 2021 Honda Civic Type R 2.0T FK8
2023+ Honda Civic Type R 2.0T or Integra Type S FL5/DE5
Fitment not confirmed for the 11th Generation (2022+) Civic 2.0NA or 1.5T