Home > Uncategorized > Adventures with DOT4 – Brake fluid in the eye, sucking with your mouth

Adventures with DOT4 – Brake fluid in the eye, sucking with your mouth

OK – call me foolhardy, call me stupid, but I thought I’d share my experiences with brake fluid.

I was bleeding the brakes on my bike – actually troubleshooting them, which meant a lot of connecting and disconnecting bleed valves. Being an occasional and very amateur self-servicer, my brake fluid draining equipment consists of:

  • 1 x small plastic drinks bottle
  • 1 x clear plastic tubing, 1/4 ” from memory

Tube goes into hole cut in lid. Brake fluid goes in bottle. Bottle inverted, brake fluid runs down pipe, and that’s your bleed kit.

However, since I have a Honda Blackbird, I’m apparently supposed to have a vacuum brake bleeding kit, because otherwise you might not be able to pump the fluid through. And sure enough, that’s what happened – my fluid level in the master cylinder got too low, air got in, and that was that – couldn’t pump it through, the handle went to the handlebar.

So… do I take it to my mechanic (how? No brakes)? Do I buy a specialist vacuum pump online, and wait? Do I attempt to build my own suction mechanism using… what? (Should have squeezed the bottle to create a vacuum, but I wasn’t confident it was that airtight). Or do I attempt to suck the highly toxic fluid out with my mouth?

[ Caution: brake fluid is highly toxic – DO NOT attempt this yourself. If you do, you do so at your own risk ]

So – I got my remaining 70cm length of clear pipe, attached it to the bleed valve, and sucked carefully, using just the front of my mouth with a very small volume to apply gentle suction. I don’t know how well you suck 0:-), but I do this using the front of my mouth, and what I guess is the front of my cheeks and tongue to apply suction. If I filled the entire space, it would be maybe 15ml, not my whole mouth, and the rear of my mouth/trachea and gullet are sealed off by my tongue, so if the fluid I’m sucking suddenly gushes forward, I should be able to contain it. I had water nearby to flush/drink, and I was careful not to swallow any saliva during this process. I did this very slowly and carefully, and watched the fluid in the pipe, never letting it advance quickly, and never letting it get more than half full. The only point I ‘tasted’ a bit was after I tipped the tube to drain some fluid, and after letting it clear, put the end back in my mouth. It would have been under 0.1ml.

So did it work? Yes. After some fluid and some large bubbles, I then kept getting this steady stream of bubbles, which seemed to clearly be coming from inside the centre of the bleed valve. The fluid didn’t rise at all. After I while, I realised that although it seemed to be coming from inside the valve, it was actually atmospheric air leaking in around the side of my pipe where it attached to the valve. I still wasn’t applying much suction, but it appeared nothing more was coming out from the fluid itself. I took the tube away and pumped the brake lever a few times, and this time got pressure, and the fluid surging in the pipe. Success!

So – takeaways? The Blackbird brake system can get in a state where you need a suction bleed kit. If you do it very carefully and keep a lot of distance between you and the fluid, and be careful to spit and wash your mouth out, you can do this, ahem, orally. And one mistake can get you poisoned. So – as I say – don’t do this yourself.


One in the Eye

Oh.. and the other thing… while I was careful to cover every painted surface with rags, and wash with water whenever a drip of DOT4 landed on the paint regardless, you (well, I) can’t experiment with bleeding brakes for 3 hours without a big mishap. For me, this was… I actually don’t know how it happened – but I got a spray of DOT4 in my face.

Big, controlled panic. Tucked the bleed hose safely away, splashed my face with the bucket of water next to me, then walked swiftly to the shower and irrigated each eye held open under the water for around 1-2 minutes. I don’t know whether I did really get it in my eyes, but I didn’t want to take the chance. I couldn’t see how anything could remain after 1-2 minutes of irrigation, despite the internet saying 10 minutes (?!) – I experienced no burning or redness, and touch wood, have had no problems 24 hours later (I’ve read that it can burn even days later… so we’ll see). I haven’t gone to a doctor, because I’ve had no symptoms.

So – I’m off to buy some DIY goggles today. It seems that I have a few escapades that require it, and it’s just a lot less hassle.

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