master cylinder brake booster question

nissansentra

Active member
Joined
Mar 27, 2012
Location
Indianapolis, IN
TDI
2005 Vw jetta pd1.9l
Hello All,
2004 vw jetta tdi gls manual transmission
I am leaking fluid between the master and brake booster. my question is can I just replace the oring behind the master cylinder and everything will be good? If this seal brakes then will brake fluid leak into brake booster thereby needing brake booster as well? Im trying to do it as cheap as possible, but also to do it right the first time.

THANKS!

Jordan
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Can't say I have ever seen that before, but yes you can get just the master cylinder for the brakes. So I suppose if that is all that is wrong you could do it that way.

The ESP cars use a different one that those without.
 

nissansentra

Active member
Joined
Mar 27, 2012
Location
Indianapolis, IN
TDI
2005 Vw jetta pd1.9l
Can't say I have ever seen that before, but yes you can get just the master cylinder for the brakes. So I suppose if that is all that is wrong you could do it that way.

The ESP cars use a different one that those without.

so the way the master and brake booster mate I wont have a problem in the future with a corroded brake booster diaphragm right? Sorry to be redundant just dont want to waste money! thanks for your help!
 

Dieselmonkey02

Veteran Member
Joined
Dec 26, 2011
Location
Edinburg, Pa
TDI
02 jetta
As long as the booster didn't take on a lot of brake fluid I think you'd be ok. Brake fluid eats paint faster than just about anything so keep the fluid cleaned up.
 

nissansentra

Active member
Joined
Mar 27, 2012
Location
Indianapolis, IN
TDI
2005 Vw jetta pd1.9l
As long as the booster didn't take on a lot of brake fluid I think you'd be ok. Brake fluid eats paint faster than just about anything so keep the fluid cleaned up.
roger that. Funny thing is it stopped leaking all of the sudden? weird huh? it does this occasionally. I will go ahead and order a new master. Thanks for all of your help

Jordan
 

Chris

Veteran Member
Joined
Jan 27, 2000
Location
Bloomfield Hills, Michigan, USA
If fluid is leaking out there you may have a booster full of fluid (or actually about half full).
The booster can function this way but at reduced boost.

The seal between master cylinder and booster is supposed to seal air from leaking into the booster.

You'll want to remove the booster from the vehicle so you can dump it out, when the time comes.
 
Last edited:

03TDICommuter

Veteran Member
Joined
Dec 8, 2016
Location
So. Cal
TDI
01' NB, 5spd
The seal between master cylinder and booster is supposed to seal air from leaking into the booster.

You'll want to remove the booster from the vehicle so you can dump it out, when the time comes.
What he said.

One thing I would say though is that brake fluid is hydroscopic. It will absorb moisture and you're going to eventually rust your booster from the inside out. It eating the paint or coating away on the inside won't help.
 

jimbote

Certified Volkswagen Nut
Joined
Jul 10, 2006
Location
spiral arm, milky way (aka central NC)
TDI
Tacoma 4x4 converted to TDI
"hygroscopic" not "hydroscopic" ... brake fluid is designed to absorb moisture to prevent brake lines and components from rusting by suspending water molecules in solution rather than it settling to low points in the system
 

03TDICommuter

Veteran Member
Joined
Dec 8, 2016
Location
So. Cal
TDI
01' NB, 5spd
"hygroscopic" not "hydroscopic" ... brake fluid is designed to absorb moisture to prevent brake lines and components from rusting by suspending water molecules in solution rather than it settling to low points in the system
Thanks for the correction. So not a concern about rusting from the inside of the booster?
 

Ol'Rattler

Top Post Dawg
Joined
Jul 3, 2007
Location
PNA
TDI
2006 BRM Jetta
Thanks for the correction. So not a concern about rusting from the inside of the booster?
Yes it's a concern. Brake fluid absorbs water out of the air. The humidity in the air is absorbed anytime brake fluid is present that is not in a sealed system or a sealed container, such as when there is brake fluid inside the booster.

Inside the cabin or outside the cabin does not matter.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
If the fluid is into the booster, wouldn't it end up in the vacuum system? Would it be possible to purge/clean it using the vacuum fitting?
 

jimbote

Certified Volkswagen Nut
Joined
Jul 10, 2006
Location
spiral arm, milky way (aka central NC)
TDI
Tacoma 4x4 converted to TDI
If the fluid is into the booster, wouldn't it end up in the vacuum system? Would it be possible to purge/clean it using the vacuum fitting?
yes, you would need to suck as much out as you can first followed by a safe solvent, rinse repeat ... but once down to mostly solvent the vacuum should boil the remainder away... i've actually thought about using the vacuum pump to evacuate the AC system after repairs but i already have an AC vacuum pump
 

Chris

Veteran Member
Joined
Jan 27, 2000
Location
Bloomfield Hills, Michigan, USA
I'm going to guess that the level of vacuum that the pump in these vehicles provides won't be nearly as effective as an AC vacuum pump.

As to the risk of ingestion, the port is up near the top of the booster housing. By the time the brake fluid reached that level you'd be experiencing a near total loss of boost (hard pedal).
 

AnotherPerson

Veteran Member
Joined
Oct 24, 2015
Location
New Orleans
TDI
1999 Beetle
My original booster had the diaphragm eaten up by brake fluid causing a vacuum leak. If you pull the booster just replace it. You can get the new upgraded booster setup with upgraded master from vw for around $250.


Sent from my iPhone using Tapatalk
 

Ol'Rattler

Top Post Dawg
Joined
Jul 3, 2007
Location
PNA
TDI
2006 BRM Jetta
I'd say don't buy it from VW. go to ID Parts, Bora parts etc for OE/OEM parts for less money.
 
Top