Loss of brakes!

Wife had a worring one yesterday.
Whilst parking after relatively slow town driving the car lurched forward as she came to stop.
She wasn't sure if the engine accelerated by itself or the brakes released.
She had to press down on the peddle hard to stop it 4 ft further on than she had planned. Good thing nobody infront of her.
I suspect she lost servo vaccum but can't see how.

Wow, worrying indeed.

At least no major damage happened this time, but could have been a lot worse.

Was it cold? Was it on auto choke still? I need to look back and see what model you own.

I've heard about this before, it is a faulty valve somewhere, it was on the Eurovan forum.

Here is some of the text:

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... here is my english version for all our members in other european countries:

As reported here our 807 suffers from a brake problem at idle speed / low engine rpm. Pushing the brake two or three times back-to-back and than once more you have to push harder to get the car stopped. Because there are individually different ways to use the brakes of a car some people maybe are not aware of a problem like this. Testing it is easy: start the engine, let it run idle and push the brakes three times back-to-back. If you got a “hard” brake when pushing once again you had the same case we had with our car: the vacuum is to weak at low rpm. As I reported before this can be a matter of safety, in all other situation the brake system of our 807 reacts quite normal. A curious thing is that I didn’t had a vacuum loss after switching off the engine, apparently there must be another reason as reported in that corresponding thread.

Another bug occured one week ago for the first time and then nearly every day. During the start of the engine (or short after it) the engine control light (the yellow symbol on the lower left side of the wheel control panel) flashes for nearly one second. At the same time a beep tone can be heard and the display shows “anomalie antipollution”. Beside that the car drives normally, but together with the brake vacuum problem and a reinitialising of the side windows (they some times do not drive to their end position in automatic mode) I put it on my list for my date at the garage today. An interesting information was that the foreman of my workshop told me during a phone call that he supposes an interrelationship between both brake and anomalie problem, because both are connected to the vacuum system.

When I got my car back in the afternoon, everything seemed to be fine. As an origin for the misbehaviour the workshop detected two leaky electrical valves with flap actuators. To understand it better here’s some technical background: The vacuum system is feed by a camshaft driven vacuum pump. Besides the brake booster, which is connected to the vacuum system via a back pressure valve, there is a vacuum accumulator, which supplies 4 of the e-valves with flap actuators (all of them CAN bus actors): one for the turbo charger (to adjust its variable geometry), one for the intake system (SWIRL), two others that are connected be a T-pipe, which are used for the exhaust recirculation (AGR) and the preheating of the intake air. The last one is necessary for the FAP system.

The reason for the weak vacuum at low rpm was detected by connecting a manometer at different locations of the system using a Y-pipe. Two of the four valves are detected to be leaky, so at idle speed, where the vacuum pump has its lowest effect, the brake system suffers from a weak vacuum. Two replacement parts are available at the workshop, but unfortunately both of them proved to be leaky, too! So they ordered new ones and swap the valves among each other until they experienced a satisfying brake vacuum. After this procedure the car was ready to drive – that’s what I’m told.

On my way home, just going to entry the motorway (Autobahn) driving nearly 80 km/h, I had to brake very hard because another car with a trailer attached and flashing warning-lights crosses several lanes to reach the lay-by lane. Immediately after pushing the brake heavily I changed from the right lane to the middle one to avoid a collision with that trailer. At the same moment the yellow engine control light went on, I heard the beep tone and “anomalie antipollution” was displayed. Unfortunately the engine was forced into emergency mode, so there was no acceleration any more and I had to change the lane back immediately to let a truck overtake me (before it crushes my back bumper). On the next parking place I called my workshop, they told me to switch the engine off, wait a little time and restart the car. After doing so the yellow engine alert was still active, but the engine runs in a normal mode again.

Back at the workshop they used a Diag-Software (called „Planet 2000“) running on a standard notebook to read out the error memory via an OBD-2 interface cable. Two messages are stored: “exhaust recirculation error” and “intake system error” (? I’m not sure how this would be displayed in English). Caused by the hard braking on the motorway the vacuum system was under great demands, so the flap for the exhaust recirculation could not reach the right position in time after this abruptly abortion of the acceleration process. As a consequence the air fuel mixture leans so much that the computer forces the engine into emergency mode. After deleting this errors from the memory and checking all operating parameters with the diag software they told me that the error was caused by the emergency braking, and that it would be no problem to use the car until they get new e-valves (the one with the flaps).

I tried. Same motorway, same problem. This time it occured at driving a constant speed (110 km/h). Everything was like before: yellow light, audio warning “beep”, emergency mode – except for one difference: I was not able to shut down the emergency mode by restarting the car. This time it takes me a little bit longer to reach my workshop, where they give me a replacement car.

So in my opinion the vacuum system, which is loaded with many consumers, is an Achilles heel of the Hdi engine. It is a complex and sensitive system, even the swapping of e-valves (two leaky, two of them OK), which are connected in parallel, causes a change of the systems behaviour. So if this problems would be solved definitely by changing all valves to proper ones, some rehibitory actions caused by unsuccessful attempts to fix the “anomalie antipollution” error became redundant - I'll keep you informed!

Best regards, Matse

Thanks for all that will test and talk to the dealer.
Car wasn't on choke had done 30 miles drive before.