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Over the weekend I worked on replacing my front brake fluid. A few years back I purchased a Harbor Freight vacuum pump to make this an easier job, but this is the first time I've used it on the Wee.

I had a heck of a time getting the pump tube to seal on the nipple. When I used the pump, it introduced air into the tube and decreased my pump efficiency. Also, it introduced the possibility of air getting into the brake system.

I should note that I'm fairly confident the bubbles I saw in the vacuum hose were not coming from the brake system -- I'm not experiencing any symptoms of air in the system before or after my project (spongy brake handle, etc.).

I tried a couple of different approaches to get it to seal, including:
- A small spring clamp, but the clamp was too long for the nipple.
- Holding pressure on it with my fingers, but it proved impossible to hold, pump, and fill without three hands.

I'm open to suggestions, as I plan to do the rear brake this weekend.
 

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You can always just bleed the old fashioned way, pump the lever, bleed, pump, repeat. The calipers and master cylinder are close enough to each other for it to be a one person job, (unless you have really short arms).
 

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I think you'll have better success if you reverse bleed the brakes. Air wants to flow up, not down, so pushing the air bubbles back up towards the reservoir is a lot easier than trying to pull it down towards the caliper. All you need to reverse bleed them is a large syringe and some tubing.

I've tried the vacuum pump for bleeding brakes, and had the same issues. You can try putting a blob of grease around the junction between the vacuum tube and the bleeder, and that sometimes works to make a seal. It's also really messy. Given the choice between the vaccum pump and just using the brake lever, I'd go back to using the brake lever.

I bought a couple large syringes and tubing from Amazon in a kit, for about 14 bucks.

Here's a good video from Youtube on how to do it. There are a bunch of others on there also.

 

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Over the weekend I worked on replacing my front brake fluid. A few years back I purchased a Harbor Freight vacuum pump to make this an easier job, but this is the first time I've used it on the Wee.

I had a heck of a time getting the pump tube to seal on the nipple. When I used the pump, it introduced air into the tube and decreased my pump efficiency. Also, it introduced the possibility of air getting into the brake system.

I should note that I'm fairly confident the bubbles I saw in the vacuum hose were not coming from the brake system -- I'm not experiencing any symptoms of air in the system before or after my project (spongy brake handle, etc.).

I tried a couple of different approaches to get it to seal, including:
- A small spring clamp, but the clamp was too long for the nipple.
- Holding pressure on it with my fingers, but it proved impossible to hold, pump, and fill without three hands.

I'm open to suggestions, as I plan to do the rear brake this weekend.
I have seen a cable tie used to help seal the hose around the nipple and that may work for you.
 

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When I bled my brakes the first time (using a manual kit, with a one-way valve) I saw a lot of bubbles in the clear plastic line from the bleed nipple. Had a hard time figuring out where it came from, and eventually concluded that this was outside air working its way through the threads on the bleed nipple, and then into the bleed nipple and into the clear hose of the bleed kit. The air was definitely not coming from inside the cylinder, and was also not getting back into the cylinder.

I have not tried, but I guess a dab of grease on the outside of the bleed nipple, where it meets the cylinder, should solve this issue. Me, I just stopped worrying and got perfect results anyway.
 

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I'm with BackPacker.
 

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Speed bleeders cost half as much. But I used a air driven tool decades ago. Worked like a charm. Only the device I used was pressurizing one, not a vacuum maker.
 

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Notacop...good tools didnt cost me money, they made me money. And if they didnt make me money, they at least saved me time and effort with professional results.
 

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I've always had the same problem with vacuum brake bleeders. The air can come in between the tube and the nipple, as well as the threads between the nipple and the caliper. Additionally, I rarely get enough draw to actually pull fluid through the system.

I use a "hybrid system"... The vacuum pump and hose is used as nothing more than a clean catch pan. The actually bleeding is done the old fashion way. I will probably eventually get the replacement bleed nipples with the built in check valve. Especially for the cars, since they are so spread out that bleeding the brakes requires two people.
 

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That's why I never liked the vacuum bleeders. I've never had them introduce air in to the system, but I don't like seeing the bubbles pull through the hose.

I've used a one man bleeder setup for years with no problems. I just use a silicone vacuum hose that feeds in to a plastic bottle. As long as the open end of the hose is submerged in brake fluid you can crack open the bleeder and pump away without any air feeding back.

 

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Speed bleeders are the way to go, super easy to install, pull the old off, screw on the new, wipe up any leakage, be sure to use some plumbers tape on threads. Once on there correctly you will never get air in system again.
 

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I was just googling about bleeding brakes and I came upon an idea: Using the engine vacuum to bleed your brake and clutch systems.

Has anybody here ever done this?

Here's how I imagine that it would work. You take a hydraulic fluid trap (such as this one: https://www.amazon.com/Mityvac-MVA6005-oz-Fluid-Reservoir/dp/B002YKBAXK/ref=sr_1_14?s=automotive&ie=UTF8&qid=1521717809&sr=1-14&keywords=mightyvac - but you could probably build one yourself using a bottle, some hoses and some good sealant). One end gets a suitable length of hose to connect to the bleed nipple, the other end is connected to the engine vacuum port or vacuum port extension.(*)

Use a syringe to suck as much old fluid out of the master reservoir as possible, then fill with fresh fluid. Start the engine. With the engine running, crack open the bleed valve so that fluid starts flowing. As soon as you see fresh fluid coming through, close the bleed valve. In the meantime, make sure the master cylinder reservoir doesn't completely run empty.

The MightyVac uses the same principle but uses a hand pump to create the vacuum pressure manually. So in that sense it should work. But how much vacuum is really required/optimal, and will the engine provide that?

An another thing: In the manual of the MityVac there's a note about ABS systems that use a high-pressure pump. "Never bleed a system with the high-pressure pump active." Anybody experience with this? You might want to use the vacuum of a different bike to bleed your bike because of this.

(*) Like many others I have installed extension tubes on my throttle body vacuum ports so that I can balance them easily. That makes attaching this contraption a breeze.
 

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The tube in the bottle is a classic procedure. Just gotta have some fluid in the bottle to insure a closed hose outlet from the air.
I guess my Mighty Vac lines never got a good seal around the caliper valve or the valves leaked around the threads.
In any case only the old pressure system and speed bleeder worked with such ease and confidence.
Set it up, open the valve and apply pressure and the old gunk flows out beautifully. No spongy feel to the handle no mo!

Oh, I didn't have to undo the factory bag mounts to get at the rear brake reservoir either. I just undid the minimum fasteners and pry the body panel back a bit and was able to pour fresh bake fluid into the reservoir. I kept avoiding a fluid change thinking I had to remove all that stuff. It was easier than I thought.
 
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