Hello,
After being inspired by HTSS_TR's post about brake bleeding using Mityvac MV7201 and vacuum bleeding I've decided to give a try and post my feedback.
Before starting to talk about Mityvac MV7201 and vacuum bleeding I would like to talk about Mityvac MV6840 and pressure bleeding. In 2015 I've purchased an Mityvac MV6840 from Amazon (
https://www.amazon.com/Mityvac-MV6840-Pr...9009&sr=1-8) and decided to try it on Peugeot 107 (2007) which is an European clone of Toyota Aygo.
After watching a couple of videos on youtube about Mityvac MV6840 I had an impression that the pressure bleeding process is safe and there is absolutely no way an air may enter the system. So, I've filled the device with 2 liters of DOT4 brake fluid, hooked up an adapter to master cylinder, pumped 15 psi of pressure and went to the rear wheel to bleed the caliper. After opening the bleeder I've waited like 30 seconds and I started to notice a bursts of air coming out of the bleeder !!!
I could not believe my eyes, so I closed the bleeder and went to the device to see what is wrong. I noticed that Mityvac MV6840 somehow was pumping air bubbles into the master cylinder and pushing the air under pressure via the brake lines.
I tried many things with Mityvac MV6840 to avoid having air bubles going into MC and eventually the only solution that worked for me was to:
1. Pump 15 psi of pressure and start noticing fluid going into MC
2. Bleed caliper for 5 second
3. Go to MC and see if bubles are being pushed.
4. If not, goto #2
5. If yes, release the pressure, goto#1
As you can imagine, doing all these things take enormous time, so I contacted Amazon, explained the problem and returned the device and I thought to solve the problem until brake fluid is due for replacement.
Two years later
I bought Mityvac MV7201 mainly for an engine oil change, and I tried it for brake fluid bleeding as well. I did not buy any special adapters, just found some tube that matches the size of the bleeders that are used on my car (Nissan Qashqai 4WD, 2010). My process was quite simple, I was doing the wheel replacement to put winter tires and each time I removed a wheel I also did the vacuum bleeding on that wheel. It was quite fast process - with around 5 pumps I was able to get a good vacuum that will result in a constant flow of brake fluid for like 5 minutes.
It was not too fast either, so I could not really miss a moment and get some air in MC, I was able to stay most of the time near MC and top up it in time. All in all, using vacuum bleeding and Mityvac MV7201 I achieved the following:
1. Less brake fluid used. If you use pressure bleeding you really need a lot of fluid in the pressure bleeder, like 1-2-3 liters
2. Less time used. It took me around 5 minutes per each caliper
3. No risk when over-pressurizing the MC and having a potential chance that it all can explode and you know, DOT4 fluid in your eyes is not the best thing
4. Somehow a cleaner job - no spills, etc