Bleeding brakes with Mityvac. Need tips. - PeachParts Mercedes-Benz Forum

rodsob · #1 11-16-2003, 10:19 PM

I'm having a little trouble with this seemingly easy task. i open the bleed nipple and attach the mityvac. the problem is, the bubbles never ever go away. shouldn't the brake fluid be coming out without bubbles? maybe the tube is not tight enough around the nipple? maybe the nipple is too loose? help! i've never bled brakes with a mityvac before. what am i doing wrong.

MikeTangas · #2 11-16-2003, 10:38 PM

The bleeder kit for the mity vac comes with an assortment of nipple fitting, different sizes to accomodate differt sized bleeder screws. Most likely you don't have a good seal at the bleeder screw and are drawing air in at the nipple fitting. The bleeder screw only needs to be opened a turn or so.

Are you under the car with a wrench on the bleeder to close it off soon as the bubbles stop? You should be, and that would put you in a prime location to try to adjust the hose nipple to get a better seal.

Stevo · #3 11-16-2003, 10:43 PM

rodsob

I could never get the Mity vac work for bleeding brakes, just didnt seem to have enough snoose, The Speedy bleeder on the other hand does work great.

psfred · #4 11-16-2003, 11:28 PM

The threads on the bleeder leak air under suction, so you will always have a stream of small bubbles if you use a MitiVac. I just use it to start the flow, then let gravity flow push the air out. Much nicer than getting someone to pump the brake pedal, and you avoid the possiblity of a rough bore in the master cylinder at the bottom eating a piston seal.

If you keep the suction pressure low, the bubbles are less of a problem.

Peter

sixto · #5 11-16-2003, 11:43 PM

Quote:

Originally posted by psfred
If you keep the suction pressure low, ...

Suction pressure?

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

rodsob · #6 11-17-2003, 08:31 AM

using gravity to bleed the brakes? please explain?

tkelley · #7 11-17-2003, 10:02 AM

If you take the bleed screws out and wrap a couple of turns of teflon tape around the threads it will seal the screw and allow bleeding free of bubbles.

MikeTangas · #8 11-17-2003, 11:07 AM

Gravity bleeding is probably the easiest method. All you do is attach a small piece of tube to the bleeder screw, place the other end in a jar and open the bleeder screw. Now just sit back and watch the reservoir to make sure it doesn't drian dry, keep it topped up until clean fluid is flowing out the tube. No pumping, sucking, pressurizing just good ol gravity doing the work.

Does not work on all vehicles though (some ABS units come to mind).

gsxr · #9 11-17-2003, 02:14 PM

Do yourself a favor and either buy a Speedi-Bleed kit, or make your own pressure bleeder from a garden sprayer and old master cylinder cover. After you use a pressure bleeder once, you'll never go back. I used a Mity-Vac for years and hated the stupid thing (for brake bleeding - it's great for vac/pressure testing).

Have fun,

benz100 · #10 05-23-2009, 12:52 AM

I agree with the feedback on Mitivac, that it has some performance problems. It works ok on motorbikes, as it produces just enough vacuum to pull the brake fluid through, but for bleeding car brakes, it is just not enough to work properly. I just purchased a brake bleeder that works off tire pressure, from http://www.speedibleed.com

This tool is very slickity slick, and probably the best brake bleeder I have ever used. They have a K400B kit for European cars, that is only $79, which includes free shipping. I just used on my W123 Mercedes, and it took about 30 minutes to change all the brake fluid, which is not bad for a 1st time using this thing. The tire concept was pretty cool, and the fluid bottle comes with a handy little air regulator to adjust the pressure from the tire down to 15 psi. The pressure in the tire was 27 psi after I finished, but I think it was already down 2-3 psi before I started. Any Benz or Beemer owners that do their own maintenance, should check it out.

Jeremy5848 · #11 05-23-2009, 01:05 AM

Me too. I could never get rid of the bubble problem and finally built a pressure bleeder. It works like a charm, especially in ABS-equipped cars. Cost me maybe $25.

curlytom · #12 05-23-2009, 02:56 AM

Benz100 – I am not knocking the Speedibleed device as I’ve considered purchasing this tool, but it appears that you have some interest in this company? Are you part owner or maybe a salesperson for Speedibleed? If you are, maybe you should state so? If you are selling this device, maybe you should refrain from critiquing other devices and just point out the strengths in yours.
In every single one of your posts you have included a link to this company’s website.
Also, here you state you just purchased this brake bleeder...

Quote:

Originally Posted by benz100

I just purchased a brake bleeder that works off tire pressure, from http://www.speedibleed.com

But, in an earlier post in 3-8-07, you stated that you had been using this brake bleeder for quite a few years...what gives?

leathermang · #13 05-23-2009, 09:08 AM

For all of you trying to be fancy.... or having trouble using one tool or another...

There are some serious benefits to have plenty of force and plenty of volume of the old brake fluid exits via the brake bleeder nipple.....

Using a power bleeder may provide those good things.... but may contaminate your left over brake fluid due to the design ( using air instead of nitrogen to power it for example)...

There are many advantages to going to the trouble of FINDING and TRAINING a helper to do the simple pumping, pushing and to watch and keep the brake cylinder cavity from going dry while doing this operation.

All the have to do is pump gently... letting you ( under the car ) know that some resistance has been felt.. then you open that farthest bleeder for a fraction of a second... ( which eliminates that ' going to far movement of the mc piston' ) ...

They learn that the most important thing is to NOT LET UP on the pedal until you signal them it is OK... so that air is not sucked up through the open bleeder nipple... pretty much impossible if you follow my instructions ( very very short 'open time' ) ... but you train them to be aware of that anyway.......
High volume and High pressure can push a lot of junk out of the brake system quickly and easily... Your helper does not need to be a genius... just follow your instructions...
and have one leg which will reach the brake pedal....

If something happens to you while under the car... you have someone who can help you get out or call 911... I am sure you macho guys will reject that idea... but I am old enough to have had stuff happen..... when I do have a helper...which is very seldom...

I feel better about my safety...

gsxr · #14 05-23-2009, 10:44 AM

I have a Speedi-Bleed kit, and it works great, except that the regulator dies after a relatively short time (dozen uses or so). But the unit still functions well. A cheaper alternative is the Motive bleeder, here's a link:

http://www.racerpartswholesale.com/category/Motive_Brake_Bleeders

I very strongly recommend pressure bleeding over either a MityVac, or manual pumping the brake pedal. The pedal method has killed more than one master cylinder because the pedal is often pushed past the normal travel, where a ridge may have built up internally, and the seals are damaged by this ridge. Then you and up replacing the M/C. This is a non-issue with pressure bleeding. The Mity-Vac never, ever worked well for me, I always had problems. Pressure bleeding has always worked great, and it's how the dealership does it.

Note that on vehicles with ASR, the factory procedure does NOT specify that pumping the pedal is an acceptable bleeding method - it only mentions using a pressure bleed unit. Click here to read the factory procedure.

leathermang · #15 05-23-2009, 11:33 AM

Which of our old diesels is equipped with ASR ?