Changed Master Cylinder. Pedal still going to floor?!
 

So 6 months or so ago I was frustrated by something in life and I vented my frustration sitting in the driveway by mashing down my brake pedal as hard as I could in a childlike tantrum fashion. Something I'd normally not admit on a forum LOL. But it was the foundation for the problem I'm having.

A mile up the road I noticed the brakes were feeling spongey.

I turned around to go home slowly and safely with half working brakes and by the time I got home the pedal was just going to the floor. At the fully-down position it would still hold my brakes fine to maneuver the vehicle in and out of the garage.

I figured it blew a seal in the 15 year old Master Cylinder and I finally got around to replacing the master cylinder a few weeks ago, and finally had time to bleed the brakes today.

During bleeding of the Front brakes I noticed that the pedal has 2 stages. The first half of travel, a kind of "click," and the second half of travel down to the floor.

When all brakes were fully bled, engine off, I thought it was weird that the pedal wouldn't harden. I could travel the pedal halfway down to just about where that "click" might happen, and then it was hard after that and wouldn't go to the floor.

I re-bled the brakes in case I missed some air. Nope no change.

So I thought I'd take it for a test drive and see how the brakes acted.

I started the car up and pedal went down to the floor exactly the way it had felt before I replaced the master cylinder!

So clearly the MC was not the culprit. But I'm not familiar with BMW's so I have no idea what else could possibly cause the pedal to hit the floor??? Zero resistance, just poof on the floor.

Brake fluid remains full in the reservoir and I don't see any fluid anywhere on the ground so I don't think it's dumping fluid anywhere. After bleeding I had pressure in the brake system. It was only after starting it again that it hit the floor.

The fact that the first stage of Master Cylinder travel never hardened up leads me to believe it's a problem in the rear half of the brake system perhaps?

Any input would be much appreciated. Thanks!

You still have air in the system.

Best is to press the brake pedal all the way down (engine off) and hold it there for a good 30 sec or more.
This way any air trapped in the MC can travel upward back into the reservoir.

Please update the thread if it works or not.

I'll try it shortly but don't have high hopes.

The pedal went from having some pressure and resistance after bleeding to immediately smacking down to the floor as soon as I started the engine, exactly as it has done before the repair.

I'm wondering if it's the ABS Pump? I know on some Ford's that a seal blowing out of the ABS Pump can cause the pedal to go to the floor.

Maybe something the booster assembly, since the issue shows up once there is vacuum...? :dunno:

You got air in the ABS pump. Take it to a dealer or an indy who has the equipment and knowledge on how to bleed the system.

I have INPA, and my understanding is that I can use it to bleed the ABS system. But for some reason I can connect to every module except DSC to activate the ABS pump. Don't really want to pay for a dealer to spend hundreds on something so simple. I built GM race car engines for 12 years so I'll be damned if I let brake bleeding get the better of me LOL. Now I have to figure out why INPA won't connect to the DSC...

Is your abs functional? No trifecta?

Do you need to search for DSC/ABS in German? I'm sure somebody here knows. I use foxwell scanner for exactly the problem you are having

E53's can be surprisingly difficult to bleed. You may need all three:

INPA method to get air out of ABS module
Pressure bleeder attached to reservoir
two-man pedal pumping bleed

A combo of the last two - pump/hold pedal while an assistant opens closes bleeder screw WHILE the pressure bleeder is attached to reservoir is quite effective.

No errors or lights indicating ABS issues.

I ordered a Foxwell to arrive today.

Just ordered a Motive pressure bleeder as well that arrives tomorrow.

Not sure how much time I'll have this week to finish the job, usually Tuesdays is my day to work on cars.

Will report back!

+1 ^
The trick is to pressurize the brake system to 20psi, crack open the RR caliper bleeder screw, bleed until zero bubbles (can take 10 mins), activate the ABS MODULE, press on the brakes 5x, continue to bleed to flow out the air that was trapped in the ABS block, repeat the ABS and manual brake activation until everything is clear and free of bubbles.
Move to LR, RF and then LF. Road test
Rebleed and you should be good to go.
Air seems to like being trapped in the RR and RF channels for some unknown reason. :)

My understanding is that you have air trapped in the ABS module and need to run the ABS bleeding function from the Foxwell service menu.

E53's also like to rust the brake lines that are directly under the driver seat. Check there for leaks in your system.

I also feel you on being frustrated. Go hammer some big nails into a stump or chop some wood. Maybe even go to a batting cage for a little session. Don't take it out on the old BMWs, they're way too fragile.

You may have to remove some of the undercarriage plastic to survey the entire brake lines.

@ual: photo giving me PTSD

So glad I live well outside the rust belt. The lines on Red looked perfect when I did the aero kit and had to remove all the cladding. I feel for you northern X owners.

Our X5 was bought in Canada so basically "if it can be rusted it is rusted."

So I just hopped on this thread to update that I have a leak in the lines under the driver seat, only to see the posts telling me to check the lines under the driver seat LOL.

What is the simplest way to repair this? Cut out a section and add in a section of line with a coupler? Or do I have to replace the entire section with probably-$$$ pre-bent line??

The FR had a ton of air in the system that came out when using the Foxwell. I got the brakes feeling 90% only to then realize I was dumping brake fluid on the ground and discovering the rotted brake line.

The car is up on a lift and it's putting a bit of pressure on the plastic panel making it hard to remove. That's a job for another day. Hopefully I can remove it without having to put the wheels back on and lowering the car down.

You need to fabricate lines with a double flare to replace the section that is rusted out. DON'T use any compression fittings for the repair. That is a NO NO.

The entire panel needs to come out including the side cladding to expose all the nuts and push pins.

There are two ways to approach this issue.
1. Replace all the lines end to end in the rear - ABS to calipers
2. Unbolt and cut out the section under the splash shield that you posted - but be aware in high rust areas, there maybe other areas causing issues in the future. Common problem that has been posted before.

What you need: Special tool to do the DIN Bubble flare ends on the lines get the good one or the cheap one your preference.
Bendable lines and compression fittings. I used this company for all of the above.
https://agscompany.com/

You will need metric Compression fittings for each rear line (10 &12 mm if my memory is correct). To connect to the existing lines you will need to add on the compression flare nut, make a DIN bubble flare on the existing steel line, and have a metric UNION to connect it. You will need to make up a repair line to connect to the junction connector at the drivers left foot area under the vehicle (Two sizes of nuts once again). I will find the link to the process and post it.

Here is the link to help you with tools, lines etc
https://xoutpost.com/bmw-sav-forums/...s-steel-4.html

ISO flare not double flare.

I did this repair on my X about 2 years ago. You can buy all three parts for about $50, the tools for about $40 and the pressure bleeder for about $50-60.

There are a pair of fittings right below the left hand driver seat and about 7-9' of line from there to the fittings at the rear left.

I posted my method to exactly copy three existing 11 or so bends in the current pipe. And also how to greatly improve the ISO (bubble) flare tool that is not completely finished from the factory.

If you are replacing the line from fitting to fitting, yes you will do a DIN ISO flare on the replacement line, but if you are splicing into an existing line, a double flare will be better because double flare fittings are more abundant in the USA since most American cars still use the double flare for brake lines.

+1 on the need to make a DIN flare not a SAE double flare. Different makes have different solutions to the same fluid connectors.

Changed Master Cylinder. Pedal still going to floor?!
 

I looked into splicing a piece but the entire lines were made of rust so I would only recommend replace end to end.

You can buy the two pieces with ends on and the 10mm one is a reasonable price like $30-40 but when I went to buy mine the 12mm ends model was about $130.

https://xoutpost.com/bmw-sav-forums/...placement.html

Excellent write up on the procedure. I'll try to find my posts describing how to clone the bends. (basically using the 3-size bending tool, put the tool on the old pipe in the 1/4" slot and put the new pipe in the 3/16" slot and bend until they match. I used nicop. No reason to use steel in a location you can't see. I'd maybe use steel for the shorter part from the abs block because it will look a little less DIY with straighter straight parts.

https://www.icloud.com/sharedalbum/#B0SGhtLJ3JIy2hw

Link to my photo album of my brake line repair. Read the comments to see what each photo details.

An old moonshiners trick to bend lines is salt, sugar, etc. in the *line and you can make complex bends without kinking the tubing.

*Not sure what could be used that would dissolve in brake fluid to flush it out before installing though....[emoji848]

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They sell bending springs for bending brake lines. You slip the spring over the line and bend the brake line. The spring will prevent the line from kinking.

1. Make sure you're using the correct flare tool and fitting. It took me about 5 trips to the autoparts store to buy the wrong fittings, use the wrong flare, ruin brake line sections, forget to put the fitting on before flaring, etc... Also, I'm pretty sure that "plastic" is fiberglass because I was incredibly itchy after messing with that. This job sucks.

2. As for tools, I bought a cheap flare tool from Advance Autoparts. I broke the first one. Advance Autoparts replaced it so all it well but it's a cheap tool and I'm sure I'd break the replacement if I used it too many times. The pin broke out of the middle of the die if I remember correctly. For brake line bending tool I just picked up the cheap $5 bending tool and it works well enough. I had no issues with the brake line collapsing.

But how does an external wrapped spring keep the id void from collapsing on a tight bend? The moonshiners had lots of tighter coils than we'll ever need though.

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Here's a video with an explanation.

https://www.youtube.com/watch?v=yKdB-szGO5Q

Kink happens when tubing can spread sideways. The spring forces the tubing to stretch more on the outside of the curve and compress on the inside rather than go wide.

I haven’t used one in over a decade because the tubing bender is easier and more precise


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Ok thanks.

I was wondering how it worked. [emoji106]

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Mike,

This is NO simple way to fix this. It has to be fixed correctly.
I did NOT replace the entire lines. Instead I "cut and pasted"...

When I first faced with the problems, I had goose bumps looking at it.
But after doing some research etc. I did the whole thing and wrote it up below.

For now, use a stick of appropriate length (detail below) and press the brake pedal halfway down to stop brake fluid loss.

Every single tip/trick is included below...


DIY: 2006 BMW E53 X5 3.0i Brake Line Replacement

https://xoutpost.com/bmw-sav-forums/...placement.html

Your can buy the brake pipes with ends already on your just need to bend:

https://www.fcpeuro.com/BMW-parts/X5...ds=34326752219

https://www.fcpeuro.com/BMW-parts/X5...ds=34326755666

As you’ll see the m12 fitting one is 5–6x the price but you get to skip the learning curve of making iso flares and just deal with bending and the mf’r of connecting the union that is up inside the axle tunnel (though with crow foot socket and one flex joint it was 4/10 difficulty just 7/10 to figure out the magic combination: look at my photo album to save a lot of effort).

To remove the plastic panel on the lift, lower to where you can set on Jack stands vs. putting on all the wheels.

When I did mine I bought 25’ of nicop, a six pack of 10mm flare ends and a couple 12mm.

All the parts and tools cost me less than the one premade 12mm ends pipe.

Take note: some of the 10 and 12mm ends will have S.A.E. sizes for the nut apparently to be compatible with flare tools typically used on brake lines (very weird like the mix match tire size).

Presumably only one pipe actually burst but good chance the other one is “made of rust” and should be replaced but you could probably do one at a time to get the system bled. When you replace the second one you should not need to do the full abs block bleed procedure as long as you bleed the last one quickly before air works its way up to the abs block.

I didn’t need to bleed my abs block when I replaced both my rear lines.

The best way to prevent brake fluid from draining out while you replace the steel pipes with ni-copper or ? is to depress the brake pedal about halfway with a stick or other wedged between seat and pedal.

That way you don’t lose all your fluid, and you likely won’t introduce air into the ABS pump.

This is discussed elsewhere on the forums, please have a search.

That makes perfect sense when your pipe already busted might as well push the full way down. that will close off the path to the master like holding thumb on top of a straw. Good call.

- Pushing the brake pedal all the way down has its own risk (small risk) of bringing the rough spot(s) on the piston, causing damage to the master cylinder seals.

- This is why the gurus recommend, during routine brake bleeding, place a piece of wood underneath the brake pedal to avoid excessive pedal travel.

- As mentioned in the DIY I posted above, pushing the brake pedal halfway down is enough to stop loss of brake fluid.

That’s a very good point about all the way down. I think I had the same issue with my brake caliper recently.