W212 - Air in brakes - help please!
05-10-2021, 12:58 AM
#1
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Thread Starter
W212 - Air in brakes - help please!
Hi all,
Car: 2010 W212 E250 CGI
Replaced brake fluid on many cars many times, but this time made a silly mistake. Somehow I managed to run the brake fluid reservoir run dry!
Refilled the reservoir, bled the system via all 4 brakes with Motive type brake bleeder. Bubbles disappeared, but at the end, the brake pedal is spongy.
What would be the best way to fix this please?
Thanks
Milo
Car: 2010 W212 E250 CGI
Replaced brake fluid on many cars many times, but this time made a silly mistake. Somehow I managed to run the brake fluid reservoir run dry!
Refilled the reservoir, bled the system via all 4 brakes with Motive type brake bleeder. Bubbles disappeared, but at the end, the brake pedal is spongy.
What would be the best way to fix this please?
Thanks
Milo
05-10-2021, 08:39 AM
#3
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You still have air in the system, you know this already.
You will need to bleed the brakes over and over until you get all the air out. It likely will require much more brake fluid than a normal flush.
Buy a whole bunch of fluid from the dealer, set aside an entire Saturday, and bleed the brakes completely.
Air in the brake system is unsafe to you and to others on the road.
You will need to bleed the brakes over and over until you get all the air out. It likely will require much more brake fluid than a normal flush.
Buy a whole bunch of fluid from the dealer, set aside an entire Saturday, and bleed the brakes completely.
Air in the brake system is unsafe to you and to others on the road.
05-10-2021, 08:47 AM
#4
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Milo,
Based on my experience, "spongy" brake pedal means one of two things: a) air in the system or b) master cylinder is is broken and bleeding fluid back into reservoir when brake pedal is engaged.
Base on your description, it is most likely that you have a case "a", you did not bleed it enough and still have some air in the system.
In case "b" if you push break pedal and hold it, eventually it will go down to the floor.
Max
Based on my experience, "spongy" brake pedal means one of two things: a) air in the system or b) master cylinder is is broken and bleeding fluid back into reservoir when brake pedal is engaged.
Base on your description, it is most likely that you have a case "a", you did not bleed it enough and still have some air in the system.
In case "b" if you push break pedal and hold it, eventually it will go down to the floor.
Max
05-10-2021, 08:49 AM
#5
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I think it’s your ABS controller that suffers when you inadvertently run the system dry.
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pierrejoliat (05-10-2021)
05-10-2021, 09:05 AM
#6
Senior Member
Have had this same scenario when I purchased a C200 that was missing a wheel, hub, calliper and half the suspension from the left rear, tried every way to bleed the brakes after repair with no success, so went to my local independent German auto specialist and they bled it with a pressure bleeding machine that fills the reservoir with fluid while pressurising the system and he just bled each wheel, he told me I had no hope of doing it any other way, he started explaining why but i think I tuned out, as I cant remember a word he said 
So I would find yourself a shop with a pressurised brake fluid bleeder and save yourself the headache.
So I would find yourself a shop with a pressurised brake fluid bleeder and save yourself the headache.
05-10-2021, 10:01 AM
#7
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IIRC you need to activate the ABS system while you're bleeding the brakes in order to get any air out of that system. The right scan tool can do that.
Key08 for the win.
Key08 for the win.
Last edited by rapidoxidation; 05-10-2021 at 10:04 AM.
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05-10-2021, 10:02 AM
#8
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Have had this same scenario when I purchased a C200 that was missing a wheel, hub, calliper and half the suspension from the left rear, tried every way to bleed the brakes after repair with no success, so went to my local independent German auto specialist and they bled it with a pressure bleeding machine that fills the reservoir with fluid while pressurising the system and he just bled each wheel, he told me I had no hope of doing it any other way, he started explaining why but i think I tuned out, as I cant remember a word he said
So I would find yourself a shop with a pressurised brake fluid bleeder and save yourself the headache.
So I would find yourself a shop with a pressurised brake fluid bleeder and save yourself the headache.
05-10-2021, 10:30 AM
#9
Senior Member
I cant remember exactly what the tech did, but there was definitely a trick to it, cant remember if someone was in the car if it was running at the time or what. it was 5 years ago now.
When I attempted to do it myself, I tried a vacuum bleeder, a small pressure bleeder, standard pump and dump, tried it every way I could, I was getting bubble free fluid out, but the pressure was not what I call good enough to bleed the system, pedal was spongey, it braked but not very efficient .
The tech told me it was a air lock in the ABS and I had no hope with what I had, he looked up what pressure the machine had to be set at before he performed the bleed and I remember him saying it was a higher pressure than he though it should be, then something about it having to be to bleed the air from the ABS unit?, like I said before, I was not really listening to him, I was just happy he sorted it.
When I attempted to do it myself, I tried a vacuum bleeder, a small pressure bleeder, standard pump and dump, tried it every way I could, I was getting bubble free fluid out, but the pressure was not what I call good enough to bleed the system, pedal was spongey, it braked but not very efficient .
The tech told me it was a air lock in the ABS and I had no hope with what I had, he looked up what pressure the machine had to be set at before he performed the bleed and I remember him saying it was a higher pressure than he though it should be, then something about it having to be to bleed the air from the ABS unit?, like I said before, I was not really listening to him, I was just happy he sorted it.
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rapidoxidation (05-10-2021)
05-10-2021, 01:55 PM
#10
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Hi all,
Car: 2010 W212 E250 CGI
Replaced brake fluid on many cars many times, but this time made a silly mistake. Somehow I managed to run the brake fluid reservoir run dry!
Refilled the reservoir, bled the system via all 4 brakes with Motive type brake bleeder. Bubbles disappeared, but at the end, the brake pedal is spongy.
What would be the best way to fix this please?
Thanks
Milo
Car: 2010 W212 E250 CGI
Replaced brake fluid on many cars many times, but this time made a silly mistake. Somehow I managed to run the brake fluid reservoir run dry!
Refilled the reservoir, bled the system via all 4 brakes with Motive type brake bleeder. Bubbles disappeared, but at the end, the brake pedal is spongy.
What would be the best way to fix this please?
Thanks
Milo
Run the engine.
Have someone help you to press brake pedal.
Open the bleed valve.
Press pedal all the way in.
Close bleed valve before pedal is let up.
Let brake pedal up.
Repeat this so you know new fluid is coming out. Get plenty of it as I would do at least 5 full presses for each brake.
MAKE SURE THE RESERVOIR DOES NOT GO EMPTY AS THIS USES A LOT OF FLUID.
In my opinion this is the best way to bleed brakes if air has entered in the system as I think it cleans that ABS controller of air too, which I don't think just bleeding with pressure or vacuum does. This just takes two people to perform.
For brake fluid change vacuum or pressure method is fine as it is just changing the fluid meaning small amount of fluid inside ABS controller does not get changed.
05-11-2021, 06:51 PM
#11
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Thread Starter
MANY thanks to all who responded here!
I suspected that there was some air trapped somewhere in the system. Most probably the ABS unit. As I wasn't comfortable with increasing the pressure bleeding pressure beyond 15PSI, I took the car to the dealership and they did it with their pressure bleeder. Yes, they found some air in the system.
I don't mind paying for the job, but I really, really enjoy working on my cars.
It would really be handy to know to do get rid of trapped air.
As Rapidoxidation mentioned, ABS activation could be the key. Would having the ignition on while bleeding be sufficient without the need for some specialised tools?
I wonder what is the maximum pressure I can use for pressure bleeding?
Thanks
Milo
I suspected that there was some air trapped somewhere in the system. Most probably the ABS unit. As I wasn't comfortable with increasing the pressure bleeding pressure beyond 15PSI, I took the car to the dealership and they did it with their pressure bleeder. Yes, they found some air in the system.
I don't mind paying for the job, but I really, really enjoy working on my cars.
It would really be handy to know to do get rid of trapped air.
As Rapidoxidation mentioned, ABS activation could be the key. Would having the ignition on while bleeding be sufficient without the need for some specialised tools?
I wonder what is the maximum pressure I can use for pressure bleeding?
Thanks
Milo
Last edited by Milor; 05-11-2021 at 07:07 PM.
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chassis (05-11-2021)
05-11-2021, 09:20 PM
#12
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Glad you got it sorted.
Folks, this is a W212, a recent model MB. Bleeding the brakes is dead simple and does not require ABS actuation. Nothing electronic is required. Just a pressure bleeder, such as the Motive system. And time and patience.
It's a dead simple process, with WIS instructions posted all over this site. Search feature will find it for you.
Folks, this is a W212, a recent model MB. Bleeding the brakes is dead simple and does not require ABS actuation. Nothing electronic is required. Just a pressure bleeder, such as the Motive system. And time and patience.
It's a dead simple process, with WIS instructions posted all over this site. Search feature will find it for you.
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MBNUT1 (05-13-2021)
05-11-2021, 09:51 PM
#13
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Thread Starter
Glad you got it sorted.
Folks, this is a W212, a recent model MB. Bleeding the brakes is dead simple and does not require ABS actuation. Nothing electronic is required. Just a pressure bleeder, such as the Motive system. And time and patience.
It's a dead simple process, with WIS instructions posted all over this site. Search feature will find it for you.
Folks, this is a W212, a recent model MB. Bleeding the brakes is dead simple and does not require ABS actuation. Nothing electronic is required. Just a pressure bleeder, such as the Motive system. And time and patience.
It's a dead simple process, with WIS instructions posted all over this site. Search feature will find it for you.
I flushed nearly 2 litres of bubble-free fluid, but some air was still trapped. I wonder if pressure higher than 15 PSI would have helped. I was not brave enough to increase it.
05-11-2021, 09:58 PM
#14
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I agree, it's dead simple... until you stuff it up like I did and allow air to get in via reservoir! .....hahaha
I flushed nearly 2 litres of bubble-free fluid, but some air was still trapped. I wonder if pressure higher than 15 PSI would have helped. I was not brave enough to increase it.
I flushed nearly 2 litres of bubble-free fluid, but some air was still trapped. I wonder if pressure higher than 15 PSI would have helped. I was not brave enough to increase it.
05-11-2021, 11:08 PM
#15
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1 Set bleeding pressure on filling and bleeding unit to 2.0 bar. 2 Remove caps of bleed screws (1, 2, 3, 4, 5, 6) on the brake calipers. 3 Connect bleed hose of bleed bottle (01) to bleed screw (1) of brake caliper. 4 Open bleed screw (1) on brake caliper. 5.1 Depress the brake pedal repeatedly until fresh brake fluid flows out free of bubbles at the bleed screw (1) of the brake caliper.Only when bleeding the hydraulic system of the brake system (after the hydraulic system was opened for repair).
To bleed the brake system correctly it is essential to pump the brake pedal throughout the entire bleeding process. Otherwise, remaining residual air can result in malfunctions and brake system failure.
In order to avoid the intake of air, do not pump the brake pedal in a jerking manner, but gradually release.
The bleed screw (1) on the brake caliper can remain open during the entire pumping process.
Total quantity of brake fluid required: approx. 1.5 liters.
5.2 Keep the bleed screw (1) at the brake caliper open until fresh brake fluid flows out.Only when replacing the brake fluid (hydraulic system of the brake system was not opened previously for repair).
Pumping the brake pedal not required. Total quantity of brake fluid required: approx. 0.75 liters.
6 Close bleed screw (1) at brake caliper. 7 Disconnect bleed hose of bleed bottle (01) from bleed screw (1) of brake caliper. 8 Repeat steps 3 to 7 on the bleed screws (2, 3, 4, 5, 6) of brake calipers.The numbering of the bleed screws (1, 2, 3, 4, 5, 6) shows the opening sequence.
9 Install caps of bleed screws (1, 2, 3, 4, 5, 6) on the brake calipers. 10 Remove cover (7) of bell housing and bleed screw cap of central clutch release bearing and perform bleeding process.On models fitted with manual transmission.
11 Attach cap of bleed screw of central clutch release bearing as well as cover (7) to bell housing.
To bleed the brake system correctly it is essential to pump the brake pedal throughout the entire bleeding process. Otherwise, remaining residual air can result in malfunctions and brake system failure.
In order to avoid the intake of air, do not pump the brake pedal in a jerking manner, but gradually release.
The bleed screw (1) on the brake caliper can remain open during the entire pumping process.
Total quantity of brake fluid required: approx. 1.5 liters.
5.2 Keep the bleed screw (1) at the brake caliper open until fresh brake fluid flows out.Only when replacing the brake fluid (hydraulic system of the brake system was not opened previously for repair).
Pumping the brake pedal not required. Total quantity of brake fluid required: approx. 0.75 liters.
6 Close bleed screw (1) at brake caliper. 7 Disconnect bleed hose of bleed bottle (01) from bleed screw (1) of brake caliper. 8 Repeat steps 3 to 7 on the bleed screws (2, 3, 4, 5, 6) of brake calipers.The numbering of the bleed screws (1, 2, 3, 4, 5, 6) shows the opening sequence.
9 Install caps of bleed screws (1, 2, 3, 4, 5, 6) on the brake calipers. 10 Remove cover (7) of bell housing and bleed screw cap of central clutch release bearing and perform bleeding process.On models fitted with manual transmission.
11 Attach cap of bleed screw of central clutch release bearing as well as cover (7) to bell housing.
This is from AllDataDIY.
Bleeder screws 1 and 2 are on the rear, 3456 are the front.
Note the 2 bar requirement (that's 29PSI!)
I stand corrected on the need for electronic intervention.
05-11-2021, 11:15 PM
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WIS procedure attached, notes:
* 2 bar (29 psi) on filling and bleeding unit
* pumping of brake pedal along with pressure bleeder if system has been "opened"
* pumping NOT required if system has NOT been "opened"
The filling and bleeding unit referenced I suspect is more than a basic Motive power bleeder or pressure pot. Either way, keep the pressure under 29 psi... for me 15 psi is enough and going up to 20-25 psi doesn't speed up the process. The procedure also requires pumping the brake pedal throughout the bleed process if the system was opened (potential for introduction of air).
A standard flush, doesn't require pedal pumping per the procedure.
Me, I always pump the pedal a few times during the bleed on each caliper with the Motive attached and pressurized. If I have a helper or am the helpee, I'll do the old-school pump/hold/bleed procedure. I've done gravity as well, takes a while, but also works. The only one I don't like is vacuum bleeding at the bleeder...
* 2 bar (29 psi) on filling and bleeding unit
* pumping of brake pedal along with pressure bleeder if system has been "opened"
* pumping NOT required if system has NOT been "opened"
The filling and bleeding unit referenced I suspect is more than a basic Motive power bleeder or pressure pot. Either way, keep the pressure under 29 psi... for me 15 psi is enough and going up to 20-25 psi doesn't speed up the process. The procedure also requires pumping the brake pedal throughout the bleed process if the system was opened (potential for introduction of air).
A standard flush, doesn't require pedal pumping per the procedure.
Me, I always pump the pedal a few times during the bleed on each caliper with the Motive attached and pressurized. If I have a helper or am the helpee, I'll do the old-school pump/hold/bleed procedure. I've done gravity as well, takes a while, but also works. The only one I don't like is vacuum bleeding at the bleeder...
05-11-2021, 11:34 PM
#17
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Thread Starter
Thanks guys. You are amazing!
Now I know how it should be done!
There is one more thing that confuses me. Everywhere I read, they say that the order of bleeding should be from the furthest to the closest caliper, in relation to the master cylinder. I thought that it should be in relation to the ABS unit as all fluid comes from the master cylinder via the ABS unit onto the calipers.
Now I know how it should be done!
There is one more thing that confuses me. Everywhere I read, they say that the order of bleeding should be from the furthest to the closest caliper, in relation to the master cylinder. I thought that it should be in relation to the ABS unit as all fluid comes from the master cylinder via the ABS unit onto the calipers.
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chassis (05-12-2021)
05-12-2021, 08:32 AM
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No.
Forget about the ABS unit.
Follow the WIS procedure. It’s dead simple.
1 right rear caliper
2 left rear caliper
3 right front caliper
4 left front caliper
No pedal pumping. Just pressure on the master cylinder.
It’s dead simple. Read and follow the WIS procedure.
Forget about the ABS unit.
Follow the WIS procedure. It’s dead simple.
1 right rear caliper
2 left rear caliper
3 right front caliper
4 left front caliper
No pedal pumping. Just pressure on the master cylinder.
It’s dead simple. Read and follow the WIS procedure.
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prktkljokr (05-12-2021)
05-12-2021, 08:43 AM
#19
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Not picking your procedure but depending on where you are in the world, That procedure is for a LH drive car, RH drive starts with the left rear, the furthest from the reservoir.
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chassis (05-12-2021)
05-12-2021, 10:10 AM
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Yes.
05-12-2021, 02:43 PM
#21
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I remember the first ABS car I owned, a 1989 Volvo 780 Bertone coupe, you had to bleed the ABS unit itself THEN bleed the wheel cylinders. *that* was a big pain.
05-12-2021, 05:10 PM
#22
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I googled a bit and found this. This is what I'm talking about:
Thanks
Milo
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Left Coast Geek (05-14-2021)
