Brake fluid leaking into booster?

[kfdisme]

I've had a brake fluid leak for a while that was kinda mysterious, as I couldnt see where the fluid was exiting the system. I've since noticed that the brakes are verrry touchy, meaning a little pedal will cause the front brakes to lock up. This vintage exploder only has rear-wheel ABS. I've noticed that the bottom half of the brake booster appears kinda wet and am assuming the fluid is leaking into it. So my questions are:

1) What do I have to fix/replace to remedy this?
2) Can this be done under shadetree circumstances?

I do have a Hanes manual and they make it appear that this has to be done professionally...

 

[roscoe 0202]

rock auto has rebuilt boosters you can change with common wrenches.
roscoe

 

[roscoe 0202]

you probably have a bad master cyl I would change that too.
roscoe

 

[Rhett]

Also make sure your vacuum modulator is ok. If it is bad then brake fluid can suck into the brake booster vacuum hose.

 

[Centaurious]

If you let it go eventually it will fill to the big vacuum hose and then you will mosquito fog at least half of Houston

 

[kfdisme]

What has actually gone bad here? Some seal between master cylinder and brake booster or what? Can I just drain the booster?

 

[nathan mayden]

The brake fluid has probably ruined the booster but the master has a seal failed and is now leaking.

 

[kfdisme]

Its been awhile but I'm finally getting around to doing this. I found a booster/MC pair on Rock Auto for $120. I thought I might try the job myself since the local shop wants about $500 to do it. There was a tech doc linked somewhere that pretty much describes the problem I have (http://www.cardone.com/techdocs/PT 50-0001.pdf).

However, I got rear wheel ABS and the Haynes manual explicitly warns against mucking with the master cylinder in this case as air can get into the "ABS hydraulic control unit" which apparently requires special equipment to bleed properly...

So is this the case and do I have to get it done by the shop, or is there a common sense way to do this myself?

 

[shucker1]

That brake booster has a monster ass spring inside that is designed to knock your teeth out if not handled carefully.

Better off to buy a rebuilt booster if you have never fooled with one before.

 

[kfdisme]

The booster/MC comes as a unit: https://www.rockauto.com/en/moreinfo.php?pk=258370&cc=1119619&jsn=778&jsn=778. Where is the danger here?

 

[shucker1]

Thought you were going to rebuild your booster.

Speed reading again...

 

[shucker1]

Be sure to fully bench bleed your new master cylinder before you put it on the truck.

If the old lines are disconnected and you don't open the wheel bleeder screws you should have a low potential to get air in the system.

 

[kfdisme]

Ok. Is there something good to use to plug the lines with to prevent too much air from getting in?
And will the air that I do get in them work its way out thru the MC by just using the brakes?

 

[shucker1]

Actually in my humble opinion I would thoroughly bench bleed the new master first.

Exchange both assemblies and leave the lines on the new assembly slightly lose letting fluid drip.

Then start the standard bleed procedure at the new master first but use both fittings simultaneously and then proceed to each wheel to completely flush out all of the old fluid.

Other members on this forum always have some good tricks to provide.