Broke down I-95, need help. Suddenly no brakes!
 

In my 93 300d, 165,000 miles. Driving up I-95, brakes suddenly hard to press, then find out engine won't shutoff. HELP! What should I check?

Thanks!

vacuum
 

I think both are vacuum aided. Loose hose? Vacuum pump?

Yep. Either a bad pump or a bad leak. My money's on a bad pump. Be careful, when some MB vacuum pumps fail they can do substantial engine damage.

Depending where on 95, I may be able to help, yet not familiar with that engine.

I'll join the chorus .... definitely a vacuum problem. Given that both engine and brake booster are affected, my guess would be something central, like vacuum pump failure. I'm shooting from the hip since I'm at work, but on my 603 I believe the vacuum line that runs to the brake booster also ports out to the ignition. So if that line broke or leaked, both brake and shutoff function would be affected. That would be much easier to fix than the vacuum pump. Unfortunately I have no idea if that's the case on the 602 ... if so it's a thick black tube from the front of the engine compartment to the booster. Again, I could be entirely wrong as I haven't toyed with that area of the car recently. Just trying. Good luck. Where on 95? Hope it's not a snowy part like here.

By the way, you still do have brakes. It's just that they will take a lot more force to apply. Probably need to use both feet.

By now, we'll assume you have either run out of fuel or have found the red "stop" button on the side of the injection pump.

If its a vacuum pump or leak, you've got brakes, just no power assist. If its a leak you may be able to find it, do a patch job to get it home or just drive rather carefully. If it appears to be the pump, AAA rollup to take it home/repair shop. Let us know.

X 10
 

If it's not a Leaking Hard Plastic Hose (or Fitting) from the Vacuum Pump to the
Brake Booster/Ignition ShutOff ...it's your Vacuum Pump and you're about
50K miles outside our Non-Georgia Tech engineering diagnostic envelope
of 100K being the SAFETY zone for these Pierburg Vacuum Pumps.

If you EVEN suspect it's the VP don't drive it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Many thanks to Klaus Kallas. He responded to an email I sent him. He was very close to where my son had the car problems and got him back on the road. It turned out to be the vacuum pump and FORTUNATELY, we seem to have avoided catastrophic damage.

Danger, Will Robinson!!! If you ever suddenly lose your brakes, stop the car!!! I did not know that the vacuum pump was still such a threat to our engines. I knew that the 617 engines had this problem, but I ASSumed that Mercedes would have come up with something better.

Thanks again Klaus!

I'll make light only because no one got hurt... that's a tall order! :D

Do you know how the pump failed? Valve elements ruptured? Bearing disintegrated? Pivot arm broke free? Was it an old style or new style pump?

Sixto
87 300D

It appeared that the bearing race came apart. Wore a groove in the cam face.

Check the magnet we put on the oil plug for small pieces of metal.

Keep us posted it should be interesting to know how this works out back in the shop.