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Mityvac help!

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I bought a Mityvac MV8000 today, hoping that I could fix the problems im experiencing with my front brake(sponginess/not full power). So I set it up as the instructions said, L joint with little adapter, 12" line, catch can, and 2" hose connecting to the unit. So I start pumping to get pressure built up, but no pressure would hold? So I just cracked open the bleeder, put the tip on and pumped away. So ten seconds of pumping all I see is just bubbles and little fluid, it almost looked like really soapy water, so I kept going and had my dad keeping the MC full, but it seemed like it was working, but the stream never changed, it looked exactly the same, so I ended up filling the canister, so I stopped pumping, closed the valve and started over, same method, same thing! I did this process three times, every time same thing, same exact lever feel as when I started!! So I am completely stumped right now, BUT I had an idea to reverse bleed with the system. So since I got two 12" hoses, I thought put one hose in the bottle of brake fluid and connect it to the bleed screw, then up on the MC run the same set-up, but on the tip, have the little rubber needle tip that fits in the diaphragm? thing on the bottom of the MC, then open the bleed crew and start pumping. Seemed like it would work, but ive thought that with alot of things.haha So idk if im doing something wrong, or my idea is rite, let me know, this is gonna be bothering me for a while :lol:

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if you can't get the brakes bled i would suspect an air leak somewhere in the line or the master cylinder itself.

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Yea you may have another leak someplace probably the MC if at all.

My guess is it's just the execution of the proccess.

I did the m-vac thing and went back to old tech. pump lever, hold it in,open bleeder,close bleeder release lever and pump up again - repeat till you get a couple MC resivoirs worth run through. Remember- be patient, don't release lever till you tighten bleeder.

Also make sure you dont have a whole different problem making the brake feel soft, like a bent rotor, or bent caliper mount or pins.

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Im sure all the parts are good. But go through two MC`s full with the old way? I always thought you do it a few times, then top off and your done? I guess it wont hurt to try tho.

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Back to the Mity Vac. If it's working right, you should be able to pull a vacuum with it (showing on the little meter), crack the bleeder open and it will pull the fluid out until the vacuum goes back to 0. Then close the bleeder valve and repeat the procedure until your pulling fresh fluid. Are you sure all your hoses on the MV are on the fittings good, no leaks? If so, and it won't pull a vacuum, your MV probably is defective.

I have an older/cheaper MV7000 and that thing is the best $29 I've spent for brake work. Use it on the bikes and truck.

One problem I have heard of people having while bleeding front brakes is when there is a loop of brake line that is going above the master cylinder. An air bubble can get trapped in the loop and won't come out with any form of bleeding. Fix it by taking the MC off and holding it as the highest point, then bleed it.

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I bought a Mityvac MV8000 today, hoping that I could fix the problems im experiencing with my front brake(sponginess/not full power). So I set it up as the instructions said, L joint with little adapter, 12" line, catch can, and 2" hose connecting to the unit. So I start pumping to get pressure built up, but no pressure would hold? So I just cracked open the bleeder, put the tip on and pumped away. So ten seconds of pumping all I see is just bubbles and little fluid, it almost looked like really soapy water, so I kept going and had my dad keeping the MC full, but it seemed like it was working, but the stream never changed, it looked exactly the same, so I ended up filling the canister, so I stopped pumping, closed the valve and started over, same method, same thing! I did this process three times, every time same thing, same exact lever feel as when I started!! So I am completely stumped right now, BUT I had an idea to reverse bleed with the system. So since I got two 12" hoses, I thought put one hose in the bottle of brake fluid and connect it to the bleed screw, then up on the MC run the same set-up, but on the tip, have the little rubber needle tip that fits in the diaphragm? thing on the bottom of the MC, then open the bleed crew and start pumping. Seemed like it would work, but ive thought that with alot of things.haha So idk if im doing something wrong, or my idea is rite, let me know, this is gonna be bothering me for a while :lol:

Did you have the pump of of the bleeder screw when you were creating a pressure? if you did that is your problem

heres a video on how to bleed brakes

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First off there is no "pressure" involved, it is vacuum. The hose you put on the bleeder screw must be a tight fit and not let any air in while pumping. You may have to remove the bleeder screw and make sure there isn't any crud in it. Also don't open the bleeder too far while bleeding or air will come in around the threads of the screw. You may also trying tapping on the master and lines with a wrench to help get reluctant air bubbles out. I bought a Mighty Vac 20 years ago when we were having problems bleeding brakes on my brothers FZR600 at a Daytona AMA event. It worked great and I still have it. I've used it on most of my vehicles including bleeding hydraulic clutches.

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When I pump the system to build vacum, I can hear air leaking from the catch can. Some where from the cap.

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I use a M-vac and the bleed nipple is where the air gets into the fluid from the vinyl hose and the threads. I put teflon tape on the nipple threads a small spring clamp on the vinyl hose so it fits tighter on the nipple. I've found the M-vac bottle to be air tight so is the lid gasket missing?

Last resort is to remove the caliper and use compressed air to force the pads together. Then pour in brake fluid and rock the caliper to remove air bubbles. Connect the hose without tipping the caliper and pry the pads apart, this pushes fluid and air back up the hose to the master cylinder. Install the caliper and operate the lever to push the pads against the rotor, you should have a firm lever.

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Ok, so my idea did absolutely nothing.lol But I noticed that on the cap that has the inlet and outlet, on the bottom there is the nozzle that shoots sucked in fluid in to the can, then on the other end there is a hole. So I took the catch can off, covered the hole and vacuum instantly built as I pumped. So I don`t get the logic behind this, when that hole is covered it builds vacuum, when it is not, i wont build any vacuum?

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Couple things to keep in mind when bleeding brakes is to squeeze the lever slowly and not to pull all the way in towards the grip. Squeezing all the way in and quickly introduce air back into the system.

This is has worked for me.

Put a short length of tubing on lower bleed nipple, other end in a bowl below it.

Take off MC cover and pump brake until some resistance is felt Loosen the bleeder slightly and pull the lever in within 3/8th inch of the grip, hold there and tighten the bleeder again. Keep repeating this process unit you see the fluid run clear. Keep the fluid from going too low in he MC and keep doing this process until all the air bubbles are out of the bleeder tube and tiny bubbles stop coming out of the bottom of the MC. IF your still getting mushy brakes after this your MC might need to get cleaned or rebuilt with a $24 kit.

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Well at the moment, there seems to be no bubbles, no matter what I do, but I can go all the way to the bar but it takes more effort than before. I guess that's how Yamaha's are?

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Well at the moment, there seems to be no bubbles, no matter what I do, but I can go all the way to the bar but it takes more effort than before. I guess that's how Yamaha's are?

Well, no bubbles is a good thing ( all the air is out of the line) and you do not want to squeeze the lever all the way to the bar. If you have to squeeze to the bar either your brake pads are extremely worn or the rubber parts on the pumper piston in the master cylinder may be worn and allowing fluid to bypass the seal so that you can't build up enough pressure. You need to take it apart and inspect all the parts. Spend the money on a rebuild kit or get an aftermarket MC and lever one on ebay for $100 as it's not worth getting into an accident over faulty front brakes.

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When it took the MC apart everything inside looked petfect.

Start with the MC. Disconnect the brake line from the MC and see if fluid is pumping out of the hole where it connects. Also put your finger over the hole and see if there is pressure building. It's also possible to put the rubber cap on the piston spring backwards when disassembling which can cause your problem. (Cap goes over and covers part of the spring not the other way around). You probably already know that brake fluid eats paint so I'll assume youre properly covering over everything as it can get pretty messy.

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bleeding bike brakes ARE a giant pain in the ass. standard automotive techniques just dont work. i've been in your shoes before. dont give up until that lever is rock solid.

1. use the mityvac and canister on the vacuum setting to empty the fluid from the reservoir

2. switch to pressure mode

3. fill the mv canister with fresh brake fluid

4. put a box end wrench on the bleeder, and connect the canister tube to the bleeder nipple, but just barely, and pump the mv to get all the air bubbles out of the tube all the way to the bleeder (it'll burp fluid out between the tube and bleeder nipple)

5. when the tube is completely void of air, fully seat the tube over the bleeder and crack it open at least an 1/8 turn

6. proceed to pump fresh fluid up from the bleeder to the master cylinder until the reservoir is full

7. tighten the bleeder and pump the lever abuot 10x real quick, and repeat from step 1 at least once (2x for sure if the system was dry/drained)

8. last step: pump up the lever and hold with firm pressure, and bleed using standard technique a couple times (sometime the caliper has a little cavity that can trap air)

it MAY be required to remove the caliper to reorient it in a way that alleviates the possibilty of trapping air at a high point

good luck.

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My mighty vac is only vacuum -__- i thought it was pressure when i nought it.lol And brside bleeding, im leaving the MC and caliper alone.

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