Hey all,

Okay so short back story. I had my brakes fail earlier this year while I was driving. I had the master replaced as well as a caliper, and haven't had a problem since. My mechanic even told me he couldn't get the master to fail, but replaced it anyway.

Flash forward to today and I'm swapping driveways in Norm. I go to push the brakes, and nothing. I pump them a bit and still nothing. I almost ran in to my garage door before a hard slam stopped the car. I tried to turn the car off, and it hesitated for about 5 seconds then shut off violently. All signs point to vacuum.

I started the car again, let it idle for a few seconds, then turned the key. It shut off like normal. So I started it again, pumped the brakes which still felt soft, then tried to turn it off. It stumbled and shut down violently again. I did these two things a number of times, and all the results were the same.

I checked under the hood and all my vacuum connections looked good and everything was where it should be. I'm starting to think this problem is what happened before it went in to the shop for the brakes.

I've put about 3,000 miles on the car since the replacement master and caliper were done, and it's driven flawlessly.

Any ideas what might be going on here? New vacuum pump? Or maybe a leak somewhere?

Thanks for the help guys.

A vacuum problem would give you hard brakes. No pedal pressure means its a bad master cylinder, or one of the calipers is leaking fluid.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

Right, this is what I though too, but the shut down problem only happens when I pump the brakes which is odd.

Fluid level is right on the dot too, but still it could be a leak. I'll have to check with better sunlight.

Oh and the door locks all work fine.

get under there with a flashlight and look for fresh fluid leaks from any of the soft lines.

The reason the shudown takes longer is because you just emptyed the brake booster of its vacuum supply by pumping the brakes, and the vacuum pump has to fill it back up so it can shut down the motor.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

Bummer, I just spent like $800 getting this fixed and had a big ordeal with my mechanic.

Hopefully Pierre does house calls.

Do you think it might be the booster? Not really all that educated in the brake department.

Check the vacuum, should be easy enough. Plug the T's to the cabin and SOV, see if you still have brake prob's, or check it right at the pump. Don't have the spec in front of me, but I went from nothing at idle to 22" Hg at idle when I swapped. I was probably just braking of of manifold vacuum at the time. Thank got for second gear.

__________________
CC: NSA

All things are burning, know this and be released.

82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times

It's hard to

more likely to

concentrate on

have an accident

two things

when you're on

at the same time.

a cell phone.

www.kiva.org It's not like there's anything wrong with feeling good, is there?

^I'll try that. I pulled a couple of the vacuum hoses to see if maybe one was loose, but didn't check to see if there was any vacuum at them.

Well it looks like I get to figure out how to replace a master cylinder.

Just ordered a new master cylinder. I actually remember having to break rather hard last night while driving, and locked the wheels up. Could that have blown it out?

you should not be able to put enough pressure on the pedal to do damage. damage might come if while bleeding you pushed a worn one farther than ever before which might cause seal damage. no pedal pressure doesnt seem like a vacuum issue. the fluid is either not getting pumped by the master or it is leaking somewhere, otherwise you would have pressure on the pedal. If you cant find fluid on the ground or at the wheels it could be a bad seal in the master piston and it is dumping fluid into the booster, I dont know for sure if it can but that fluid might be travelling back in the vac line so be sure your vac pump or other components dont have break fluid in them

__________________

1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

I had some brake issues not too long ago. I would get not brake boost if I used the brakes 2-3 times in a row, so if felt like I had no power brakes. I checked the vac pump and it was pulling 23, but would drop to 0 if I applied the brakes firmly a couple times. I swapped the pump with a spare and the problem went away. If you've replaced your master and slave I would try a pump rebuild or a used one and see if that helps.

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Slow down, and decompress..

Question 1: Did the pedal go to the floor?

Question 2: What is your current vacuum reading?

My best guess at this point from supplied data:
* Vacuum pump valves failing?
* Main vacuum line from pump to booster damaged?
* Brake vacuum booster damaged by previous leaking master cylinder?





Have a great day.

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1983 300D
1984 190D
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I just went through all of this last week. My thread on that is pretty recent somewhere. My wife had the exact same symptoms you described.

Start at the vacuum pump and work your way towards the firewall. Check the vacuum at the pump first, then pull and check the main line, etc.., etc...

Our problem turned out to be low vacuum at the pump caused by failing check valves. I'm ordering the rebuild kit today.

__________________
AJ

1985 300D (SOLD)

^Is that the kit from AutohauzAZ? I might try that too should my vacuum pump seem to fail.

Also I haven't had this problem in a long time, but I used to have shifting issues. All I would do is unplug the line and plug it back in and it would reset. I'm guessing I've had a vacuum issue for a while now that's grown.

No... I order a bunch of parts from here occasionally. This is one of those times. I'm ordering it from AllPartsExpress (top of the page) along with a couple glow plugs, turbo drain o-ring and some other stuff.

Troubleshoot the system before you buy the kit. Your pump "might" be OK. No sense on wasting your money on a kit you don't need.

__________________
AJ

1985 300D (SOLD)