I can't bleed brakes!
Thread Starter
Senior Member
Joined: Oct 2009
Posts: 333
Likes: 2
From: NYC
2007 C280 4Matic
I can't bleed brakes!
I went out and bought a motive power bleeder, and 2 quarts of MB fluid.
I turkey bastered the old fluid out of the master cylinder, hooked up the motive bleeder after filling it and the master cylinder with fluid, then pressurized the system to 10 psi. I did the passenger rear caliper first. I attached the clear hose, opened the bleeder and let it run. Everything went smooth.
After that I tried doing the driver side rear caliper and for the life of me I can't get the bubbles to stop, I've gone though .5 liters of fluid and I still have tiny bubbles coming out of the clear line. I'm doing everything the same.
Help! What should I do differently?
TL;DR: How do I get all the air out of the brake line properly?
I turkey bastered the old fluid out of the master cylinder, hooked up the motive bleeder after filling it and the master cylinder with fluid, then pressurized the system to 10 psi. I did the passenger rear caliper first. I attached the clear hose, opened the bleeder and let it run. Everything went smooth.
After that I tried doing the driver side rear caliper and for the life of me I can't get the bubbles to stop, I've gone though .5 liters of fluid and I still have tiny bubbles coming out of the clear line. I'm doing everything the same.
Help! What should I do differently?TL;DR: How do I get all the air out of the brake line properly?
MBWorld Fanatic!
Joined: Sep 2010
Posts: 1,434
Likes: 4
From: Raleigh, NC
2005 C230K, 2019 Honda CR-V, '74 Lotus Europa
Did you loosen the bleed screw too much? Just loosen it enough to get the fluid to flow.
Another possibility is that an upstream fitting is loose or there some damage to the line or hose. You didn't mention replacing hoses or any damage so this seems unlikely.
Another possibility is that an upstream fitting is loose or there some damage to the line or hose. You didn't mention replacing hoses or any damage so this seems unlikely.
Last edited by ncmudbug; Nov 14, 2010 at 11:24 PM.
Thread Starter
Senior Member
Joined: Oct 2009
Posts: 333
Likes: 2
From: NYC
2007 C280 4Matic
My theory was that when I pressurized the fluid I dissolved air into the fluid and when the fluid came out the other size the lower pressure caused the bubbles to form. The only way I can fix that is with a vacuum bleeder. Which I hope isn't the case because it means I've bought a useless brake bleeder.
As other people have had success with this system I hope that's not the case.
MBWorld Fanatic!
Joined: Sep 2010
Posts: 1,434
Likes: 4
From: Raleigh, NC
2005 C230K, 2019 Honda CR-V, '74 Lotus Europa
You are probably right if you ALWAYS maintain positive pressure. If not, it remains a possibility. I've seen it happen with the old two-man pump and bleed method. If you always maintain positive pressure, then it sounds like you have a leak somewhere.
I bought a Motive bleeder too, but I haven't used it yet so I'm a veteran of somebody pumping the brakes and opening the bleed screw.
I bought a Motive bleeder too, but I haven't used it yet so I'm a veteran of somebody pumping the brakes and opening the bleed screw.
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Joined: Jun 2008
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Try just cracking the bleed screw open as e says.
Also try bleeding the brakes with the car idling & the ABS system active. See if this changes the pattern of what you are seeing.
Also try bleeding the brakes with the car idling & the ABS system active. See if this changes the pattern of what you are seeing.
