Front brakes won't bleed, even with vac! - PeachParts Mercedes-Benz Forum

imagesinthewind · #1 03-19-2011, 07:57 PM

So, you may remember that I needed a new master cylinder back in Sept or so.

I had some trouble getting the front brakes to bleed. Took everything off and tried again. The back bled easy. The front still nothing. I bought and tried a mightyvac and while I can draw some brake fluid out of the left front, when the brake is pressed, no fluid comes out on it;s own. The right front has brake fluid coming out, but not shooting out like the back does.

I had a vac leak, but I used black gasket stuff and that is solved.
So, What the H3LL am I to do now? Even the mighty vac doesn't seem to help. And my hand hurts from trying. Is ther a way to get the vac to blow instead?

I can feel the air sucking and blowing on my finger if I hold it over the screw.
YES there is a full front chamber on the res, I pumped it up with the little pump on the top of the res. If I can feel the air sucking and blowing, see a small bit of fluid blow out of the screw, then there is not a blockage.
I am loath to take it all off again, I'd lose the gasket I made.

What can I do, please help! Thanks to all!

Ginny
78 300SD

vstech · #2 03-19-2011, 10:27 PM

check your pm. I sent you good instructions!
or give me a call...
vacuum is a horrible way to bleed brakes!

leathermang · #3 03-19-2011, 10:43 PM

Quote:

Originally Posted by vstech

....vacuum is a horrible way to bleed brakes!...

Thank You, AMEN !!!

Ether · #4 03-19-2011, 10:56 PM

Quote:

Originally Posted by vstech

vacuum is a horrible way to bleed brakes!

X2!

I tried that a few times and gave up in frustration. For me, the only way to go is with a pressure bleeder. You can build one for 25 bucks or less that will work great.

leathermang · #5 03-19-2011, 11:13 PM

You need pressure.. .it can be from a pressure bleeder.... or from the master cylinder.. but you need pressure to count on doing a good job on all types of systems...

My problem with pressure bleeders is that I suspect the fluid not used when the can is opened and put into it... is used later... stored in the bleeder ... having absorbed moisture... that problem could be overcome by pressurizing it with Nitrogen or Argon or some other dry gas...instead of AIR or just get rid of what is not pumped into the system at the end of the bleeding process.

whunter · #6 03-19-2011, 11:30 PM

Some Facts About Brake Hoses:
#1. The the industry standard average safety life of a brake hose is six years. FYI data SAE: J1401, J1703, J1705, J1873, J1406, J1288, J1403, J1833, J1402.
#2. Brake hoses deteriorate from the inside as well as the outside.
#3. Moisture is absorbed into brake fluid systems through brake hoses.
#4. Contaminants in brake fluid act abrasively on the inner wall of brake hoses.
#5. The brake hose reinforcing fabric deteriorates through expansion and moisture.
#6. High operating temperatures contribute to the deterioration of hoses.
#7. Brake hoses swell with age and restrict flow.
#8. Generally all brake hoses on a vehicle deteriorate at the same rate, So all hoses should be replaced if one is found to be faulty!

Brake hose failure mode:

#A. Rupture (burst hose) = age, exercise (too many miles) or impact are the typical cause.

*B. Partial internal collapse = the inner ply becomes damaged/detached acting as a partial restriction and/or one way valve.

#C. Full internal Blockage = the inner ply becomes damaged/detached acting as a plug = brake pedal still feels good but there is no brake application.

Brake bleeder recommendation
http://www.peachparts.com/shopforum/showthread.php?p=455818

Power Bleeder or what?
http://www.peachparts.com/shopforum/showthread.php?p=707359

Brake bleeder - power bleeder Homemade
http://www.peachparts.com/shopforum/showthread.php?t=117258

Brake system bleeding, master cylinder bleeding
http://www.peachparts.com/shopforum/showthread.php?p=1127978

.

Quirky Mercy · #7 03-19-2011, 11:46 PM

I use a jelly jar and a clear rubber tube. put one end of the tube in the jar and the other on the open bleeder. as you pump it will push out the air and suck fluid in. make shure the res is full and pump until all air is out. works well for me. I was thinking the rear res was for the front?

Ether · #8 03-19-2011, 11:55 PM

Quote:

Originally Posted by leathermang

You need pressure.. .it can be from a pressure bleeder.... or from the master cylinder.. but you need pressure to count on doing a good job on all types of systems...

My problem with pressure bleeders is that I suspect the fluid not used when the can is opened and put into it... is used later... stored in the bleeder ... having absorbed moisture... that problem could be overcome by pressurizing it with Nitrogen or Argon or some other dry gas...instead of AIR or just get rid of what is not pumped into the system at the end of the bleeding process.

I just dispose of what's left. A little wasteful, but not a bad trade off in my opinion, considering how easy it is to do the job.

imagesinthewind · #9 03-20-2011, 12:11 AM

I got great instructions from vtech.
Seems I was trying to bleed the brakes the american car way.
I will try the German car way and report back.

She's been sitting since Oct and I really want to drive her again
now that winter is about gone and Spring is in the air. She needs
a bath. . .

vstech · #10 03-20-2011, 12:25 AM

... american and german hydrolic brakes are all the same... ya needs pressure, not vacuum... and you have to close the bleeders before you release the pedal!

jimbonaz · #11 03-20-2011, 04:28 AM

Quote:

Originally Posted by imagesinthewind

So, you may remember that I needed a new master cylinder back in Sept or so.

I had some trouble getting the front brakes to bleed. Took everything off and tried again. The back bled easy. The front still nothing. I bought and tried a mightyvac and while I can draw some brake fluid out of the left front, when the brake is pressed, no fluid comes out on it;s own. The right front has brake fluid coming out, but not shooting out like the back does.

I had a vac leak, but I used black gasket stuff and that is solved.
So, What the H3LL am I to do now? Even the mighty vac doesn't seem to help. And my hand hurts from trying. Is ther a way to get the vac to blow instead?

I can feel the air sucking and blowing on my finger if I hold it over the screw.
YES there is a full front chamber on the res, I pumped it up with the little pump on the top of the res. If I can feel the air sucking and blowing, see a small bit of fluid blow out of the screw, then there is not a blockage.
I am loath to take it all off again, I'd lose the gasket I made.

What can I do, please help! Thanks to all!

Ginny
78 300SD

Pull the bleeder screws and make sure they are not clogged up with corrosion and gunk. Pressure bleeding is the best wich is easy with 2 people but the bleeders can't be plugged up.

leathermang · #12 03-20-2011, 09:27 AM

Quote:

Originally Posted by Quirky Mercy

I use a jelly jar and a clear rubber tube. put one end of the tube in the jar and the other on the open bleeder. as you pump it will push out the air and suck fluid in. make sure the res is full and pump until all air is out. works well for me. I was thinking the rear res was for the front?

It may have worked well for you.
but it is not good advice for bleeding brakes...and we have no way of knowing how well it really worked for you... specifically whether it left some old brake fluid in your system....this is also the reason you bleed the longest line first... so that when the others are bled you know that NEW fluid it being run into them....
You need a secure one way function.. new fluid in at the top, air and old fluid and junk pushed out at the bottom with force. Not ' some ( unknown amount ) out at the bottom and sucking back in'...
There is also the matter of the threads of the bleeder potentially letting air back in on the suck as that flows easier than the new ( and lower situated ) new fluid...
The regular system is easy and fool proof. Don't try to get tricky or lazy on Brake items...
And do not think I do not know how much trouble it is to get help for this procedure done right if you do not have a bleeder....as I do not... and train the helper.... 40 years of being a one man operation on mechanicing...

benhogan · #13 03-20-2011, 09:34 AM

replace the brake hoses. if they are original, they probably need replacing anyway. they are fairly inexpensive and it's cheap insurance (especially since these are front brakes)

leathermang · #14 03-20-2011, 09:40 AM

Quote:

Originally Posted by benhogan

replace the brake hoses. if they are original, they probably need replacing anyway. they are fairly inexpensive and it's cheap insurance (especially since these are front brakes)

X 1000

Very few people understand how short the actual safe life of those lines is.
I know that reads funny but the ' is' refers to ' life' ...
As Whunter's post shows... they can look good on the outside and delaminate on the inside.. which can cause one side to LOCK in the clamped position...
I and others have had this happen in the past... discussion in the archives...
They are cheap ....and just for the record.. NEVER HANG YOUR BRAKE CALIPERS BY THE BRAKE LINES... make a wire hanger to hold them.

imagesinthewind · #15 03-20-2011, 10:29 AM

Front brake lines are about 6-7 years old. Done by PO about a year before we bought it. Found a receipt for that when going through the stuff after purchase. I'm confident those are in goos shape.

Will be nice to get her moving again, I think she's felt left out over the winter.