3D printed brake fluid cap

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bmartin

Member
Joined
Dec 31, 2015
Messages
18
I wanted to share this with everybody for the sake of lost fluid caps of the future.

I was adding more brake fluid today and accidentally dropped the cap below the motor. Being as there is a solid floor, it didn't hit the ground but instead ricocheted off the floor presumably never to be seen again.

In a panic, I went to Tinkercad and designed a new cap. After some modifications and good measurements, I created a cap that seals on tight and is designed to fit the threading of the Leaf. No idea if this will fit other vehicles, or even if it will do the job correctly, but hey, $13 I don't have to spend.

And here's the final product: https://www.thingiverse.com/thing:1848415/

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As long as it doesn't get too hot under the hood (I'm not sure.. No idea what temps are under there), PLA should work fine.
I think it's OK to about 122 degrees Fahrenheit before it starts to soften..
Otherwise ABS or PETG should be better choices...

Downloading that model just in case.. ;-)

desiv
 
Great job and great idea, my only concern is that with brake fluid, the primary concern is moisture, so I assume the original cap has a rubber or silicone seal built in. Brake fluid is hygroscopic and absorbs water from the atmosphere. Without that same type of seal, I would not want to run it long term.
 
Other concern is that brake fluid is a great solvent and tends to turn some plastics brittle or to putty. Its one super paint remover too.

There is of course also the $2,600 + cost of the MakerBot Replicator 2 and the filament costs that kinda detracts from the economy of it all. For an emergency to get by until you can get an OEM approved cap formulated to withstand long term use with brake fluid that's a pretty good idea.
 
This solution is not acceptable. Brake fluid will absorb moisture if left in open air.
Replace the cap. If you have waited for weeks you have to flush the fluid too.
 
powersurge said:
It is amazing that we can do this stuff. Is this made of plastic? If so, what kind of plastic?
I use PLA in my printer. I think technically it is a corn starch, bioplastic if you will: https://en.wikipedia.org/wiki/Polylactic_acid

Firetruck41 said:
Great job and great idea, my only concern is that with brake fluid, the primary concern is moisture, so I assume the original cap has a rubber or silicone seal built in. Brake fluid is hygroscopic and absorbs water from the atmosphere. Without that same type of seal, I would not want to run it long term.

This is a good idea, I didn't think about moisture. I will spray the bottom of the cap with something like this (Flex seal): https://www.amazon.com/Permatex-82099-Spray-Sealant-oz/dp/B0018PW15I
 
Too late. Hope this chemical will not be dissolved with DOT fluid.
Otherwise you might ruin something much more expensive than that cap.
Also I hope that super-cap has has specified maximum pressure rating.
 
Everything in our atmosphere is under pressure.
What you ask is: "is there a pressure difference between two sides of cap".
If there would be absolutely no pressure then air moisture would just ruin brake fluid.
 
the PLA should be fine. I would be worried about the lack of a proper seal/bladder.

you can print this on a $200 printer btw.

I would not be too keen to trust my brakes to it though :) not without a lot more info.
 
Normally I'm all for 3d printing useful things but this is a bad idea. I know PLA will melt if left inside a hot car and I assume that under the hood can get just as hot if parked in the sun.

Also a few years back I was changing out the brake fluid on my motorcycle and accidentally spilled some on the fairings (body plastic), which are made of ABS. They started dissolving almost immediately.

So right off the bat, the 2 most-common-by-a-vast-majority printing materials are disqualified.

On top of that, as others have mentioned, brake fluid is hygroscopic - and 3d printed objects are rarely watertight, let alone airtight.

Spend the $13 now for a real part and save yourself a headache that's coming sooner rather than later. Keep an eye on the color of the brake fluid just in case it's absorbed a bunch of moisture already.
 
derkraut said:
Is the brake fluid reservoir under pressure? I don't think so???

No, and it is important to note that brake fluid reservoir caps have a small vent to allow equalization of pressure with the atmosphere. With some type of baffle to prevent fluid leakage and dust ingress. It's a very small amount of air movement, but it's not a pressure-sealed system. Also as someone mentioned, a flexible bladder that is meant to accomodate transient changes. There's a bit of engineering in these little items.
 
Thanks for sharing. You can also find all information about printing material via http://3dinsider.com/pla-vs-abs-plastic-pros-cons/. You can find here difference between PLA ans ABS.
 
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