Hey guys! I got my 2004 e320 V6 (petrol / LPG) a month ago or so. It really is in inmacular shape to be honest - I was looking for a good w211 for a long time. It's 260k km on the clock, previous owner took extremely good care of it. So far everything looks fine, but I had a nasty surprise a day before yesterday. Right after the first cold start for the day (around - 5°/ -7° C outside temperature) and after I pressed the brakes this message popped on the dash, beeps and all whistles:


This message appeared.

The brake pedal stiffened extremely hard and I had no brakes basically. Thankfully I was still just parked outside my apartment block. Turned the key back, took it out, restarted the car and it was all gone. No sign of anything. Fast forward the same day, but in the evening - I've driven the car around 50 km or so during the day (highway) and I cold start it after a few hours (same temperature outside, maybe even colder), start driving and around 4/5 minutes later, while pressing the brakes the same thing happens, only this time I was on a crossing and narrowly avoided collision. Same procedure - turn the key, take it out, restart - everything is fine and dandy. I drove it the whole day yesterday - no signs of trouble.

I forgot to mention that both cold starts I didn't wait at all before pressing the brakes (the second time I just took off right away), I am mentioning that because when it's cold I usually give the car 1/2 minutes idle and then put it in D and give the tranny oil 1/2 minutes to get going. Didn't do that when all this happened.

Also I don't think it's the SBC going out, because it was replaced by MB official dealer under extended warranty 70 000 km ago. But I don't really know? Could it be it?

​​​​​​Personally I think it might be a battery or something. I think I should check the voltage. Small battery is 4 years old, the big one I don't know. Also I got the "Electrical malfunction ; Conviniences switched off." message a couple of times since I have the car (usually when it's cold) but never paid much heed to it since I figured it's typical w211 behaviour. After I drove the car for a bit and started it back again after a while it always went away.

Any ideas?

 

I'll personally thank you to stop driving the car today and to fix the issue before you drive it again.. Get the codes read (there are codes stored but a cheapo reader won't retrieve them) and go from there. The Benz extended warranty is still in effect; use it before you kill someone.
It does sound like you might need batteries too; I'll bet there's a code in your computer for an error there.

Cars that stop reliably are arguably better than cars that go.

 

The computer is saying: "No brakes, Stop!"

But how to stop then...???
Honest shortcut: don't drive this vehicle!

I 've been in a car with busted brake lines... it scared the living Jesus out of me.

 

It’s been a couple of days since first posted, but I sincerely hope the car is in the shop. None of the things mentioned are the”typical” W211 quirkiness. Even if the SBC was replaced once, the warranty still covers it. And yes, turning off the key will sometimes clear the error, for it to come back at the worst time. Our 2003 W211 had 300 000 km when it was retired. The SBC was replaced once. All the strange behavior was around non-safety related systems: radio & entertainment, door locks, remote key fob, sunroof.

 

Yeah, I guess the other possibility is that it failed and the guy is dead.

But assuming he's still alive, it could still be the SBC pump. It's a rebuilt pump so it could fail sooner than expected. That's typical of how they fail, no brakes and then brakes when you restart it. There's a backup SBC battery and I think you usually get warning notices when the battery voltage is too low. It's a 25 year unlimited miles extended warranty so the SBC is still covered.

 

OP he ded
RIP