What is an egg-shell color, that gets dirty quickly, and completely sticks out amongst all the black plastic and silver metal under the hood of your CivicX? The OEM Coolant reservoir tank that’s what. While it’s an important part of your cooling system, its odd shape, and fading plastic make it look like an afterthought in your engine bay. It’s as if Honda completed everything under the bonnet and was like “oh snap we forgot to add a place to fill your coolant” and then Ted was like “it's fine just put it in the corner over there”. Let’s dive into this little container, what it does, and how we intend to make a cooler version.

The coolant reservoir, aka coolant expansion tank, is a simple device with a couple of functions for your Civic. First, it is a reservoir to hold extra coolant. Second, it is the place to refill and add more coolant to your cooling system. Third, since it is the highest point in the cooling system it is also where you bleed the system to get rid of any air that might get in it from servicing. Lastly, and perhaps the most important,  is that it pressurizes your cooling system to raise the boiling point of the coolant/water mixture in your engine. 

So the coolant tank is an important piece of your car and it is not something that you can just do without. Like you have to have one. However, we don’t think you have to have an ugly one.

The OEM coolant expansion tank is made from thick and hard plastic. This is because it is under pressure. On average the coolant tank will operate under 1.1 to 1.3 bar (16 to 20 psi) of pressure at any given time. Because of this, the plastic has to be very hard and rigid so that it can hold up. It also needs to take the heat. The coolant mixture in your engine can get up to 250 deg F in an engine overheat situation and the tank can’t melt and make a mess under the hood. Since the tank is also a reservoir and a place to add coolant, the outside of the tank has markings that indicate max and min levels. This way you know if you need to add some more water or if you are topped off just right.

The plastic fades to an off-white color over time and in some cases can become brittle and crack leading to an overheating situation. We fix this by making a nice metal piece that will fit ALL the 10th gen Civics. We know we want a piece that looks great under the hood and does its job. A coolant tank that takes the pressure but does it in style. Of course, it needs to be an easy bolt-on piece that will not require a ton of modifications for you to install.

You can see the direction we are headed in the images above. Let us know what you think by dropping a comment below and be on the lookout for part 2 of this blog series in about a month. 

Vincent
Co-Founder