Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes ShopForum > Technical Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 01-20-2010, 09:04 PM
Austin85's Avatar
Smells like Diesel..
 
Join Date: Jun 2005
Location: Boca Raton, Fl
Posts: 2,722
Can lost vacuum = lost brakes?

Any connection in common that could have caused this?

Last weekend for 1st time the vacuum locking on the 300SD (81) stopped

working automatically. No hoses knocked off...so I figured lost vacuum somewhere.

Then when I first drove on Monday I have an obvious soft brake pedal, going to the floor...

Almost no brakes. My rears were just done 4 months ago, and the fronts were checked same time and were ok 4 months ago..

The brake fluid level is showing full So I assume no leaks......

Any suggestions for possible issue ? Is a connection possible ?

Thanks,

Austin
__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

Reply With Quote
  #2  
Old 01-20-2010, 09:12 PM
Registered User
 
Join Date: Sep 2006
Location: Middle TN
Posts: 3,445
Quote:
Originally Posted by Austin85 View Post
Then when I first drove on Monday I have an obvious soft brake pedal, going to the floor...

Almost no brakes. My rears were just done 4 months ago, and the fronts were checked same time and were ok 4 months ago..

This is the SD? Soft pedal usually indicates air in lines. Since the system is closed, assuming that you haven't opened the lines, expect internal leak in the master. Physically check front & rear calipers for leaks. Put a vacuum gauge on a line & measure vacuum from vacuum pump. I would expect a hard pedal if the problem were caused by lack of vacuum.
__________________
85SD 240K & stopped counting. 84SD 180,000. Thinking of painting both.
Reply With Quote
  #3  
Old 01-20-2010, 11:12 PM
Registered User
 
Join Date: Jun 2006
Location: Southeast
Posts: 1,542
Unless you know

Unless you know what you're doing, trust me, you don't want to mess with your brakes.
Reply With Quote
  #4  
Old 01-20-2010, 11:24 PM
dantheman67's Avatar
Registered User
 
Join Date: Jan 2010
Location: California
Posts: 172
Quote:
Originally Posted by jbach36 View Post
Unless you know what you're doing, trust me, you don't want to mess with your brakes.
Can you cite your reasons for not working on one's brake system.
__________________
1982 240D 4spd, 327,000mi
Reply With Quote
  #5  
Old 01-20-2010, 11:29 PM
Crazy_Nate's Avatar
Registered User
 
Join Date: Jan 2008
Location: Hampton Roads
Posts: 567
Wouldn't a lack of vacuum be a hard pedal, not a soft pedal?
__________________
1982 240D, sold 9/17/2008
1987 300D Turbo
W124.133 - 603.960, 722.317 - Smoke Silver Metallic / Medium Red (702/177), acquired 8/15/2009
262,715 and counting
Reply With Quote
  #6  
Old 01-20-2010, 11:38 PM
okyoureabeast's Avatar
Rogue T Tolerant
 
Join Date: Jul 2009
Location: North America
Posts: 1,392
Quote:
Originally Posted by dantheman67 View Post
Can you cite your reasons for not working on one's brake system.
Needing to stop from 73 mph to 0 in a quick amount of time.

I don't mess around with my brakes. I have my indy do that stuff. I would rather pay the money to have someone who's done this before do it right then me be cheap and cause the death or damage to myself or someone else.

Granted practice makes perfect. If you want to go ahead and bleed your brake lines promise me that when you're all done you will put both of your feet on the brake peddle and push in as hard as you can. Then pump the brake and do a lot of slow and fast tests around your neighbor hood.

If you have a brake failure, have it occur when you're going slow near your house and not on the highway
__________________
Quote:
Originally Posted by Yak View Post
Going back to the original post: "Can you get the vac to blow instead?" No. Vacuums are low pressure so they by nature "suck" and nature abhors them.
1984 380SL

Last edited by okyoureabeast; 01-21-2010 at 12:40 AM.
Reply With Quote
  #7  
Old 01-20-2010, 11:41 PM
dantheman67's Avatar
Registered User
 
Join Date: Jan 2010
Location: California
Posts: 172
Quote:
Originally Posted by okyoureabeast View Post
Needing to stop from 73 mph to 0 in a quick amount of time.

I don't mess around with my breaks. I have my indy do that stuff. I would rather pay the money to have someone who's done this before do it right then me be cheap and cause the death or damage to myself or someone else.

Granted practice makes perfect. If you want to go ahead and bleed your brake lines promise me that when you're all done you will put both of your feet on the brake peddle and push in as hard as you can. Then pump the brake and do a lot of slow and fast tests around your neighbor hood.

If you have a brake failure, have it occur when you're going slow near your house and not on the highway
Fair enough.
__________________
1982 240D 4spd, 327,000mi
Reply With Quote
  #8  
Old 01-21-2010, 12:20 AM
4x4_Welder's Avatar
Registered User
 
Join Date: Dec 2009
Location: Poulsbo, WA
Posts: 504
Locks and brakes are separate vacuum systems on that car- Locks are run by the pump in the trunk, brakes off engine driven pump.
If you had to make a hard stop recently, that could have caused the brake failure. In the master cylinder, corrosion builds up in the areas the pistons normally do not travel in. When you stomp on the brakes, the pistons go into this corroded area, and the corrosion (aluminum oxide or iron oxide depending on what the master is made from) cuts the seals allowing fluid to leak past. This results in extremely soft pedal and total loss of brakes in a short time.
For a test, with the car idling, put your foot on the brake lightly. If the pedal slowly drops, then the master is done and needs to be replaced. Having this failure, you should also replace all the rubber flex hoses in the brake system. Chances are they are just as old as the master.
Reply With Quote
  #9  
Old 01-21-2010, 12:33 AM
Austin85's Avatar
Smells like Diesel..
 
Join Date: Jun 2005
Location: Boca Raton, Fl
Posts: 2,722
Quote:
Originally Posted by 4x4_Welder View Post
...........
For a test, with the car idling, put your foot on the brake lightly. If the pedal slowly drops, then the master is done and needs to be replaced. Having this failure, you should also replace all the rubber flex hoses in the brake system. Chances are they are just as old as the master.
Sounds about right...thank you..
__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

Reply With Quote
  #10  
Old 01-21-2010, 01:38 AM
Diesel911's Avatar
Registered User
 
Join Date: Sep 2007
Location: Long Beach,CA
Posts: 23,519
Baring an external leak or not enough Brake Fluid I vote the Master Cylinder also.

It could be an internal leak in the Master Cylinder or an external Leak at the rear of the Master Cylinder; that leak will leak into the Brake Booster where it is no visable.

If someone does not want to work on their Brakes that is OK. However, DIY on the Brakes next to an Ignition Tune-up, and Filter Changes has to be one of the most often done DIY items.
__________________
84 300D, 82 Volvo 244Gl Diesel
Reply With Quote
  #11  
Old 01-21-2010, 05:24 AM
layback40's Avatar
Not Banned
 
Join Date: Nov 2009
Location: Victoria Australia - down under!!
Posts: 4,023
Take note of 4x4 & Diesel !! they are on the money. Time to replace the master an flexible lines. Brakes tend to fail when they are used hard. Like in an emergency, you dont need that risk. Its ok to replace the parts yourself, Unless you know what you are doing I would suggest not trying to rebuild your master. Dont use second hand brake parts from a junk yard. Only new or professionally rebuilt parts.
__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving
Reply With Quote
  #12  
Old 01-22-2010, 12:43 AM
Diesel911's Avatar
Registered User
 
Join Date: Sep 2007
Location: Long Beach,CA
Posts: 23,519
The rebuild kit for a Master Cylinder cost nearly as much as an exchange Master Cylinder and you get no warranty.

On the other hand I ended up with a rebuilt Master Cylinder that only lasted about 1 year.
I did exchange it under warranty but I did not put on the exchaned one. I bought a new FENCO Master Cylinder (at the time Autozone had a good price on it; has gone up since then). That has solved my problem. (I had the same Pedal to the Floor Problem as the OP.)

There is nothing difficult about rebuilding your own Master Cylinder if only the Seals are shot as the kit replaces the Seals and Pistons. The problem is if the Master Cylinder bore is rusted, pitted or erroded inside.
If the bore is not good putting a new kit it will at best get you buy for some months or at the worst not work at all.
The Merceds Master Cylinder has a pin the goes through a slot in the front Piston of the Master Cylinder. If someone wanted to rebuild it they would have to find some clever way to pull the pin out; or you cannot slide the Piston/Seal Assy. out of the Cylinder.
__________________
84 300D, 82 Volvo 244Gl Diesel
Reply With Quote
  #13  
Old 01-22-2010, 02:37 PM
Austin85's Avatar
Smells like Diesel..
 
Join Date: Jun 2005
Location: Boca Raton, Fl
Posts: 2,722
1981 300SD at Mechanic NOW...

Waiting for another call back...........


So far NOT THE MASTER CYLINDER...........



ANY OTHER POSSIBLE IDEAS....HE IS CHECKING CALIPERS NEXT...


AA
__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

Reply With Quote
  #14  
Old 01-22-2010, 03:18 PM
rrgrassi's Avatar
mmmmmm Diesel...
 
Join Date: Jun 2006
Location: Royse City Tx
Posts: 4,872
Any air leaks? Holes in the rubber lines at the wheel, worn out caliper piston seals, and even rusted through metal lines can cause problems.
__________________
RRGrassi


70's SPM #5608 Fairmont A-4 MOW car

06 VW Jetta TDI 210K miles

03 VW Golf TDI 5 speed 372K Miles

RIP--Lost in fire...82 300D 322K was My Daily Driver-On the search for a w126 now...

90 Dodge D250 5.9 Cummins/5 speed. 350K
Reply With Quote
  #15  
Old 01-22-2010, 03:34 PM
Austin85's Avatar
Smells like Diesel..
 
Join Date: Jun 2005
Location: Boca Raton, Fl
Posts: 2,722
Quote:
Originally Posted by rrgrassi View Post
Any air leaks? Holes in the rubber lines at the wheel, worn out caliper piston seals, and even rusted through metal lines can cause problems.
and the answer is............. .........leaking Rear Caliper ...Still under warranty

New one arrives tomorrow morning....No cost.


WHEW!......



..
__________________
'87 924S
'81 280SEL

Sold ->

81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 06:18 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page