BMW M5 Forum and M6 Forums banner
1 - 20 of 28 Posts

·
Registered
Joined
·
31 Posts
Discussion Starter · #1 ·
I'm preparing to change out my brake master cylinder next weekend, and I'm really dreading bleeding the system. Last time I did it, I was never happy with the results. This time I want to make sure and get it right. Most of the DIYs don't mention DIS. The only one that does has this excellent post from nightkrawler http://www.m5board.com/vbulletin/e3...289-brake-bleeding-dis-5-7-a.html#post3996490 but it doesn't touch on what to do if you've introduced air upstream of the ABS module (like I will when I replace the MC).

I figure before I bleed the ABS/DSC pump I'll need to somehow get out the air introduced during the MC change, otherwise activating the ABS will pull air into the pump (I would think). Can I just use a power bleeder for this (without using DIS)? Can I do this at only one caliper or do I need to do all 4 (effectively flushing the whole system twice)? Since I'll be introducing air in both circuits, I figure I'll need to do at least 2 calipers, if not all 4. If so, that's $20 worth of ATE straight into the recycling bottle :(.

Once I've done that, what is the procedure to follow? Do I activate the presupply pump first (as I've seen in one DIY video or do I "Start Bleeding" (Option 1) first? Do I activate presupply pump for all 4 corners or only the fronts? How about the "Pump 5 times" recommended in DIS. What exactly am I doing with the bleeder screw while pumping? Do I leave it open the whole time, leave it open until the end of the 5th pump (using a helper to hold the pedal while I close the bleeder), or open/close it like conventional 2-person bleeding? Also, nightkrawler's post says "repeat on each corner till air is out of system". Does that mean repeat the above at one corner until all the air is out, then move on to the next, or does it mean keep going around the car (RR, LR, RF, LF, RR, RL, RF, LF, etc.) until all the air is out?

There's a lot of good info out there, but almost every post seems to contradict with the one before it. I'm looking for a proven, agreed-upon algorithm that will "guarantee" (dangerous word, I know) a successful bleed. Thanks in advance for the help, and maybe someday this can be part of the DIY listing.

A little background: 2001 M5, I have DIS, I have a Motive Power Bleeder, I have a helper, and I plan on bench bleeding the MC on the vehicle (buying the TRW part, will I need to buy a separate bench bleed kit?). I do not have a vice for bench bleeding on the bench.
 

·
Registered
Joined
·
10,642 Posts
That is a good post and a very good question. I do this often and don't use dis to do it. As much as I post many times a day I am not sure I have the time to explain everything that I do.
In order to avoid DIS you need to push fluid back up to the master, which is easy. Fluid can be stored in the calipers, but it is very bad to push fluid up through a closed ABS solenoid. That is where the time for me comes in and has been a factor every time I have done this. Easy to open a noid with a 9 V battery, we do it for vanos.
I suppose if I figure out the correct way and which solenoids I will save time the next time I do this. Some noids need to stay closed and some need to be open. This is easy with a couple of 9V batteries.
The basics are this you pull the pads and let the calipers fill with lots of fluid. Your caliper must be perfect so look at rebuilding them first if there are any that are question marks.

This is where I have to check, so take it with a grain of salt and check if you proceed. On some systems there are 3 noids per caliper and some 4 per caliper. I think ours are 4, but I don't remember. I would have to check but you could too.
If you are going to push fluid back to the Master the relief solenoids need to be open, 1 sometimes 2 other times. Never push fluid back thru a relief noid when it is closed. That is standard for all brake jobs. There are a ton of brake jobs gone bad because someone pushed the caliper open with the noids all closed.

Out of time, that should give you some questions so ask away. I will limit other posts and concentrate on this post. I would give you more but you have so few posts and no creds. So help me and lets get a very good topic explained by being smart, as I suspect you are from your post.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #3 ·
Thank you for your reply. I'm not looking to "avoid DIS" though. I have DIS and I'm trying to find the "by-the-book" instructions for how to use DIS, my Motive, and my helper in the right order. I had previously considered storing fluid in the caliper as you mention, then pushing it back up, but since I'm not happy with the results of my last bleed, I figure a full flush is in order. Now that I've read your warnings against pushing fluid up with ABS solenoids closed, I'm glad I didn't try this method on my own!
 

·
Registered
Joined
·
10,642 Posts
God you are fast. I guess I am happy you don't want to do a non DIS. That said the Dis way only works 50% of the time 40% guys have softer pedals. 10% the brakes don't work. You decide.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #5 ·
Well, the first time I tried it I was one of the 10%. Had to order more fluid and try again. That time I was one of the 40%. Hoping the third time's the charm!
 

·
Registered
Joined
·
10,642 Posts
Personally I have been a 0% all the time. So you have maybe got better results. Maybe you have never gotten 100% which was my point. Then again newbie experts we see thousands of you head to the dealers.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #8 ·
Main symptom is very poor pedal feel (spongy). Although I suppose this could be due to my previous bleeding job not being 100%. Also, I have what feels like very minor leak-down (it's only there if you're looking for it) when holding the pedal down for extended periods. No other symptoms.
 

·
Registered
Joined
·
3,969 Posts
its a pain and probably going to take a few trys to get all the air out. first bench bleed the MC, then install it and fill with fluid, put the pressure bleeder on and bleed till there is no more air coming out, rr, lr, rf, lf, then with the pressure bleeder still on use the service function in dis to bleed the abs, same pattern. the 5 pumps is done after the abs module stops its activation, then you close the bleeder. tis explains this if still unclear.
 

·
Registered
Joined
·
2,630 Posts
I'm a little cloudy on my memory of this work, but I've done 2 master cylinders on these cars and somehow was able to completely bleed the system the first time, both times. Maybe I was over the top with the number of times I bled each wheel. My process, as far I remember it, is to leave the reservoir in the car so that you don't have to bleed the clutch line. Next, when I install a new master, I leave the lines loose, fill the master and then tighten the lines a little later. MAYBE this pushes some air out, maybe not. I just did it anyways. Next I hook up the laptop... now the first time I did this was 5 years ago, and I THINK I used the DIS process (almost positive). I went around the system twice to bleed it. The other time I did this work was last summer and I used INPA and simply activated the solenoids one at a time. Or maybe two at a time? Inlet and Outlet? Went around the car maybe 4 times doing it with this method and again, first test drive firm pedal. The ABS has been activated in real time on both cars and the pedal never changed, so I know the air is out.

Edit to add: For my bleeding method, I use a clear hose from the bleeder and into an empty Mountain Dew 16 oz or whatever bottle. I prefill a little fluid to make an air barrier. Next, I open the bleeder and make sure it stays open and then I slowly pump the pedal a bunch of times. I can tell based on bubbles in the line and the color of the fluid if I've bled it long enough. I go through each wheel at least twice. Is this the most efficient way? Absolutely not. Is it the cheapest one man system? At zero dollars I'd say yes.
 
  • Like
Reactions: strangerover

·
Registered
Joined
·
31 Posts
Discussion Starter · #11 ·
its a pain and probably going to take a few trys to get all the air out. first bench bleed the MC, then install it and fill with fluid, put the pressure bleeder on and bleed till there is no more air coming out, rr, lr, rf, lf, then with the pressure bleeder still on use the service function in dis to bleed the abs, same pattern. the 5 pumps is done after the abs module stops its activation, then you close the bleeder. tis explains this if still unclear.
Thanks, nightkrawler. Should I be activating the presupply pump at any time in this process?
 

·
Registered
Joined
·
13,017 Posts
Next, I open the bleeder and make sure it stays open and then I slowly pump the pedal a bunch of times.
Are you sure about that? If talking about the bleeder screw on the caliper, you pump the pedal while it is closed (3-5 pumps), then open, steady pressure on pedal until pedal hits the floor, then close BEFORE releasing the pedal off the floor. Repeat. Tapping the caliper with a rubber hammer helps move air bubbles out.

Did I miss something?

Regards,
Jerry
 
  • Like
Reactions: herrubermensch

·
Registered
Joined
·
31 Posts
Discussion Starter · #13 ·
Are you sure about that? If talking about the bleeder screw on the caliper, you pump the pedal while it is closed (3-5 pumps), then open, steady pressure on pedal until pedal hits the floor, then close BEFORE releasing the pedal off the floor. Repeat. Tapping the caliper with a rubber hammer helps move air bubbles out.

Did I miss something?

Regards,
Jerry
Do you see what I mean about lack of consensus?

Most of the sources I've read (and that's a large sample size) say that the traditional open-pump-close-release method is not required when using a pressure bleeder. Of course by "most", I mean approximately 51% ;)
 

·
Registered
Joined
·
13,017 Posts
Do you see what I mean about lack of consensus?

Most of the sources I've read (and that's a large sample size) say that the traditional open-pump-close-release method is not required when using a pressure bleeder. Of course by "most", I mean approximately 51% ;)
I was referring to the 2 person pump method. I thought that was what was being referenced. Motive is good for a first round, but at the end of the day, I find the old fashioned 2 person pump method is the best method to finish off a brake bleeding session.

Regards,
Jerry
 

·
Registered
Joined
·
3,969 Posts
follow the same procedure for the remaining wheels. so bleed regularly w/pressure bleeder, then open bleeder screw, do the activation w/pressure bleeder still connected, then pump pedal 5 times, then close bleeder screw, repeat.

running a line from the bleeder screw into a container of brake fluid is a good way of bleeding also as when you pump the pedal you don't have to worry about sucking air into the line as the end of the hose is submerged in brake fluid.
 

·
Registered
Joined
·
351 Posts
Get another person who can operate the brake pedal following your instructions only. If you can't find that then it's just a PITA.

1) Open bleed screw on caliper furthest away from fluid reservoir
2) Get assistant to depress pedal - catch fluid in old towel or big sheet
3) Close bleed screw
4) Get assistant to lift foot off of pedal
5) Check fluid level in reservoir - top up with new fluid if needed
6) move onto the next wheel furthest from the reservoir and repeat until new fluid appears from bleed screw

If you have a good assistant who does exactly what you direct and you don't have too many beers, you will get this done without drama in under an hour easy.
 
  • Like
Reactions: jamiepeers

·
Registered
Joined
·
2,630 Posts
follow the same procedure for the remaining wheels. so bleed regularly w/pressure bleeder, then open bleeder screw, do the activation w/pressure bleeder still connected, then pump pedal 5 times, then close bleeder screw, repeat.

running a line from the bleeder screw into a container of brake fluid is a good way of bleeding also as when you pump the pedal you don't have to worry about sucking air into the line as the end of the hose is submerged in brake fluid.
Are you sure about that? If talking about the bleeder screw on the caliper, you pump the pedal while it is closed (3-5 pumps), then open, steady pressure on pedal until pedal hits the floor, then close BEFORE releasing the pedal off the floor. Repeat. Tapping the caliper with a rubber hammer helps move air bubbles out.

Did I miss something?

Regards,
Jerry
Yes. What I put in bold from nightkrawler is what I am accomplishing. This allows me to bleed the system by myself.
 
  • Like
Reactions: herrubermensch

·
Registered
Joined
·
13,017 Posts
Yes. What I put in bold from nightkrawler is what I am accomplishing. This allows me to bleed the system by myself.
I see. I do that even with the 2 person method, it is good advice no matter how you bleed the brakes.


Regards,
Jerry
 
  • Like
Reactions: herrubermensch

·
Registered
Joined
·
4,490 Posts
Something I have noticed over the years- some bleed nipples leak air past the threads when opened, some don't. If they don't, the one-man technique with the hose end below the fluid in the bottle works well. But if air does get sucked past the threads when the pedal is released, that method is no good.

Another thought, if you are bleeding with a high-mileage m/c and you haven't flushed the fluid regularly, it's a bit risky pushing the pedal all the way to the floor. Moisture accumulated in the m/c over the years can corrode the part of the bore not swept by the u-cup seals during normal braking. Now you push the seals way past their normal travel and they scrape over the corroded area.

Malcolm
 
1 - 20 of 28 Posts
Top