I have tried everything... vac booster
 

I bagged my trip to Yellowstone .. snow and no brakes held me up.
I posted earlier and got some great help but I am stumped. I will keep this simple and straight forward.

80 Merc 240D 190k miles runs like a dream

I decided to repack my front wheel bearings. I had to spread the caliper to remove it from the rotor. No problem... worked fine and repacked the wheel bearings. As I drove it ... it became obvious I had no booster at that point. Very stiff brake and no booster . I looked for vac leaks. BTW the key woould no turn off the motor now as well... so had to be a vac leak.
Ihave no locks or other vac lines hooked up other than the two brwon that go in and out of the key. IP shutoff works great btw when I add any vac with mouth suction or miteyvac.
I pulled off the main vac line to the booster and replaced with a direct setup from the vac pump on front of motor to the vac booster.
I am pulling 20 hg and holds well. Vac booster does not work.
I do no believe the booster is bad but thats all I have left. I have a spare booster but don't want to go through the brake/cluthc bleed unless necc.

any suggestions.. I am pulling my hair out
remember I have only one vac line on the entire car right now..( I unhooked the key vac lines as well) from vac pump direct to booster . When driving around I get a boost as I slow then the pedal get real hard and I have to stand on it....I just don't believe in coincedences... eveything was fine befoe the bearing pack and now no booster.

confused.... all opinions appreciated.. forgive my ast type/spelling and punctuation.

Bennett

I'm not really understanding you!

You removed the caliper to pull the hub in order to add grease, or re-pack the wheel bearings, and then re-installed the caliper.

How should anything you did have anything to do with the vacuum, or with the vac booster?

Did you touch anything associated with the vac and vac booster system? If so what?

There are questions that remain when I read this.

1) If you pulled off the main vacuum line to the booster and you replaced it with a "direct setup", please describe, in detail, what a "direct setup" is. The main line has a proper fitting at the booster end and it does not leak. I'd be very suspicious of a "direct setup" and question why you did this??

2) If the vacuum shutoff is not functioning, you need to find and correct the vacuum leak that causes the ignition switch to go without vacuum.


When you properly correct the original cause of no vacuum to the shutoff, I'm confident that the booster will function properly.

If you are positive that the booster is getting vacuum (which I am not), then put a T in the line to the booster and monitor a vacuum gauge in the setup and report back.

I guess no Yellowstone put other breaks on, but anyway, whatever you did to effect vacuum supply should not have, or have anything to do with, re-packing wheel bearings! You must have inadvertently, mistakenly, interfered with your vacuum system somehow. Tell us what you did....step, by step..

answer:

I am positive I am getting 20 hg vac from the pump... I pulled the new hose off the booster and put my vac gauge on teh new line going direct to the vac pump =20HG and it held after shutoff as well.
Checked the same way with the original plastic hard line with the TEE and pulled full vac.

Have you had a mysterious brake fluid leak you could never find.......where you have to top up the master cylinder a couple times a year or more? Yet you could find no leak?

I have retraced my steps ... I jacked her up and spread the brake calipers.. I don't know how that could affect the booster but somehow it did.
I repacked the bearings and got in and noticed weak pedal at first. I started it up and drove around the block and pumped the pedal and I got that hard pedal feel and have to exhort great pressure to stop! I never had the hood opened during the whole bearing pack scenario...
Remember this car has only 3 vac lines in operation, vac locks are not an issue.... the main line from teh vac pump to the booster and the 2 brown operating the IP shutoff... the shutoff and booster were never a problem and worked flawlessyly unit I spread those calipers..which was mmaybe 1/8" at the most.. no brake fluid came ouot of teh master.
:confused:
I do appreciate the continued help btw.. keep the questions coming.

No leaks... we have put 4000 miles on since owned in JULY

Ok...then your mastercylinder hasn't started to leak and filled up the booster like my W116 did last year...leading to hard brakes.

I'm at a loss to tell you the problem. You seem to have full vac at the booster, but the vehicle behaves as though the booster is not functioning.

However, the chances of coincidence whereby the booster fails at the exact moment that you perform work on the calipers is just about nil.

Are you sure that you are not mistaking a "high pedal" for a "hard pedal". Do you definitely need more leg to stop the vehicle??

Something you did to upset the calipers is at fault! mAYBE YOU DIDN'T PUT THEM BACK IN, or on, PROPERLY!

God knows, but it is not, I repeat, not, involving, or should have involved the booater, or vacuum system, to remove and replace right or left calipers period... so how does vacuum come into this picture....explain with even mooooore detail pleaSE!

BHD, could you please explain this to me in a little more detail? This caught my attention because I have also had to top off the reservoir twice in the year I've owned the car. Sorry not trying to hijack the thread.

From when I bought my car (W116) 3 years ago I needed to put fluid in ever few months...not a lot just a little.well last year my brakes got intermittantly hard and I finally noticed the slowly sinking pedal symptom sitting at a long light. I could never find ANYTHING that was even damp with fluid anywhere.

When I got a replacement master cylinder adn went to replace it I found the booster 1/2 full adn I mean up to the center hole full of brake fluid.

Now since that does not do good things to the booster I went out and got a remanufactured booster also... Which via a call to Partsamerica.com I found out they were getting one for a tidy price of $114 exchange....junkyards wanted $99 for one.

What happens is effectivly it reduces your vacume capacity and resulting brake assist. The Master cylinder rear seal had been slowly leaking for several years to drink that much fluid.

As pads wear its normal for the level to drop...but not as fast or as much as I was experienceing.

here's pic of whats goin on...

ask away

check out my small vac hose going into cab from the IP pump to shut-r-down
that where you can't read that yellow writing in the middle right.

:D
thats the small black tube going into the cab.. I suck on it to shut down the IP

ya.. redneck...I suppose

How does one test a brake booster if I have one out of the car ready to go into another one?

I don't think a mighty vac will do it??