[Hawkdog]

So, tonight I attempted to change my brake fluid on my M4Cx to prep for an upcoming track day. My dad and I were going to do the old 2-man system. We started by sucking a bit of fluid out of the reservoir and then went to bleed the passenger rear caliper first. My dad depressed the brake pedal and I opened the bleed screw. Fluid started coming out as expected and after about a second, I started hearing a click noise about every second. At each click, the fluid would momentarily stop coming out. After about 6 clicks, the fluid stopped coming out completely, so I closed the bleed screw. After that, we tried a few more times to bleed that screw, but no fluid came out. We checked the reservoir and definitely did not run it dry at any point.

So now, I’m getting warnings that the brake system is jacked up as well as the chassis stabilization (assuming that has to do with the brakes not working). I put everything back together and took it for a very slow test drive, and the brake pedal is very soft and the brakes have about 10% of their normal power, so I’m fairly certain there is air in the line. Also verified this in that we only put about 350ml into the car, but collected about 500ml through sucking out the reservoir and what came out of the caliper bleed screw.

So, I humbly ask the collective mind for your help. What did I F up, and how do I fix it?

[LOW4LYF]

Originally Posted by Hawkdog

So, tonight I attempted to change my brake fluid on my M4Cx to prep for an upcoming track day. My dad and I were going to do the old 2-man system. We started by sucking a bit of fluid out of the reservoir and then went to bleed the passenger rear caliper first. My dad depressed the brake pedal and I opened the bleed screw. Fluid started coming out as expected and after about a second, I started hearing a click noise about every second. At each click, the fluid would momentarily stop coming out. After about 6 clicks, the fluid stopped coming out completely, so I closed the bleed screw. After that, we tried a few more thimes to bleed that screw, but no fluid came out. We checked the reservoir and definitely did not run it dry at any point.

So now, I’m getting warnings that the brake system is jacked up as well as the chassis stabilization (assuming that has to do with the brakes not working). I put everything back together and took it for a very slow test drive, and the brake pedal is very soft and the brakes have about 10% of their normal power, so I’m fairly certain there is air in the line. Also verified this in that we only put about 350ml into the car, but collected about 500ml through sucking out the reservoir and what came out of the caliper bleed screw.

So, I humbly ask the collective mind for your help. What did I F up, and how do I fix it?

ISTA...

You can't bleed manually anymore, there's a job in ISTA and the tool tells you what to do.

[Hawkdog]

Originally Posted by LOW4LYF

ISTA...

You can't bleed manually anymore, there's a job in ISTA and the tool tells you what to do.

Ok, I’m obviously a dumbass when it comes to this. Is there somewhere that explains ISTA and how to obtain and use it? I see some brief mentions of it on a few threads when I search, but am not seeing anything definitive that explains it.

Found a couple videos on google for an F80 brake bleed using ISTA…is G80/G82 the same? If so, I’m really confused because the ISTA instructions for the F80 say to do a manual bleed at all four corners first, which is exactly what I was doing when things went to shit.

[Celticsfan34life]

oh lord. I was about to do this lol

[Hawkdog]

Originally Posted by Celticsfan34life

oh lord. I was about to do this lol

Besides getting MY car fixed, that’s the other reason I wanted to post this despite making myself look like an idiot. I’ve bled brakes on dozens of cars over the years and know what I’m doing for the most part. Was hoping this thread might save someone else from the fun. Still hoping someone can come along and read what I did and shine some light on why the car did what it did.

[beachBmmr]

Originally Posted by Hawkdog

Besides getting MY car fixed, that’s the other reason I wanted to post this despite making myself look like an idiot. I’ve bled brakes on dozens of cars over the years and know what I’m doing for the most part. Was hoping this thread might save someone else from the fun. Still hoping someone can come along and read what I did and shine some light on why the car did what it did.

The car has an electronic master cylinder and is brake by wire. Opening the bleeder valve and bleeding confuses the computer. So does leaving the caliper pistons retracted and starting the car.

You might be able to do this manually with the car totally off but you will likely get a critical brake warning and lose brake assist as the car sees the fluid pressure change and thinks theres a leak.

happily, You can clear the errors with bimmer link.

[moproblems]

I have bled the rears but used the pump and open technique. You cannot just hold the pedal on these cars you have to be fast or the car will error. If you'd like to have a copy of ista I can lead you that direction.

I will say the ista procedure is not for the faint of heart. All 4 corners must be up in the air and you have to follow the procedure to the T or you will also have issues.

[Hawkdog]

Thanks guys. Sounds like we need to start a sticky thread for “Think twice before you attempt to DIY xxxxx on the G80/82/83”.

Taking it in to the dealer for the fluid change in a couple hours. They said they can put the castrol SRF in for me.

[xXMPowerXx]

I’m not sure why’d you get fluid out of the reservoir first?

I get that you are trying to get all the old fluid out, but taking fluid from the reservoir?

Well, it is what it is. I like the vacuum bleeding technique.

Maybe disconnecting the battery before attempting this might help?

[Ximian]

Originally Posted by xXMPowerXx

I get that you are trying to get all the old fluid out, but taking fluid from the reservoir?

I do it to avoid mixing high temp fluid and regular brake fluid and also because it's much quicker than letting the rear right caliper drain it all. I do dry pressure bleeds only which has extra "refilling the reservoir" steps so saving time anywhere is nice.

[xXMPowerXx]

I can understand trying to save a little time, but air in a brake system can be a nightmare!! Try doing Ducati rear brake bleeds, they hide an extra high curve in the brake line that is not always obvious and you scratch your head to find it.

I like that extra “cushion” of brake fluid in the reservoir to help me stop before I vacuum too much out.

To each there own, I suppose and THANK you for posting as we all would think BMW would make this common maintenance job a rather easy thing to do on an M car.

[Hawkdog]

Originally Posted by xXMPowerXx

I’m not sure why’d you get fluid out of the reservoir first?

I get that you are trying to get all the old fluid out, but taking fluid from the reservoir?

Well, it is what it is. I like the vacuum bleeding technique.

Maybe disconnecting the battery before attempting this might help?

Agree with the other posts - less to flush through if you suck out the reservoir a bit.

Not sure about disconnecting the battery. I imagine it would prevent the DSC from sensing the “leak” and activating, but my guess is you’re still going to have a problem when you hook the battery back up.

Dealership tech spent about 2 1/2 hours getting it right today. As others have posted, it sounds like even with ISTA, the process is a nightmare. Requires multiple iterations of bleeding at each corner and also as previously mentioned the entire car has to be in the air with all 4 wheels off. I sure as hell won’t be trying this again. It’s only about $150 for the fluid change at the dealership…well worth it IMO.

[Celticsfan34life]

When you were bleeding, you left the valve open for 5-6 seconds at a time? I usually have someone pump and hold until the peddle goes to the floor and then repeat while keeping the reservoir full. Was any air getting into the system while you tried?

[Hawkdog]

Originally Posted by Celticsfan34life

When you were bleeding, you left the valve open for 5-6 seconds at a time? I usually have someone pump and hold until the peddle goes to the floor and then repeat while keeping the reservoir full. Was any air getting into the system while you tried?

That is what I was doing. 100% sure the reservoir was never dry. My guess is that the car detected a fluid “leak” and closed a valve in the brake line somewhere upstream of the bleed screw, immediately cutting off the flow of brake fluid to the caliper. As soon as that happened, the brake line backfilled with air through the bleed screw. That would have only taken a split second after the flow of fluid was cut off.

[Celticsfan34life]

Maybe with the battery terminal off I could have some luck doing it. Worth a shot before paying the money to have someone else do it lol

[ATX_M3]

Originally Posted by xXMPowerXx

I’m not sure why’d you get fluid out of the reservoir first?

I get that you are trying to get all the old fluid out, but taking fluid from the reservoir?

Well, it is what it is. I like the vacuum bleeding technique.

Maybe disconnecting the battery before attempting this might help?

I was planning to do the vacuum bleeder approach as well - did you have any issues?

[xXMPowerXx]

Originally Posted by ATX_M3

I was planning to do the vacuum bleeder approach as well - did you have any issues?

My M4 is on a ship on it's way to me!

But after reading this thread, I may just pay the dealer!

[ATX_M3]

Originally Posted by xXMPowerXx

My M4 is on a ship on it's way to me!

But after reading this thread, I may just pay the dealer!

Ya - I'm actually looking into one of those "mobile mechanics" to have them do it for the first time in my driveway & I watch + take notes. I swapped fluid on my F8x but seems like a whole new task on the G8x…ugh.

[Kinglagos]

Using a vacuum pump kit on the reservoir should work properly I think, I am about to do it myself soon but was wondering if anyone has done it before.

[Jon H]

Is this the correct program to bleed the brakes yourself?

https://www.bimmerdiagnostics.com/

[MBoriPerf]

any update anybody on how do this DIY?

[TheM3Chase]

Wow this is an incredibly good heads up. Thanks for sharing