Comments on: The Zoe braking system

By: Oleksiy Protas

Oleksiy Protas — Mon, 04 Nov 2019 11:58:40 +0000

Bit of a necroposting here, but I’ve driven a Zoe downhill that both didn’t have its traction battery attached and 12V disconnected. Sure the vacuum was off, but the car did brake, indicating there’s a layer of mechanical fallback on good ol’ unpowered hydraulics if everything falls apart.

Adds to the version that the car above had hydraulic system malfunctioning in first place, not related to electronics.

By: Jeroen Meijer

Jeroen Meijer — Sat, 11 Jun 2016 20:42:18 +0000

In reply to Oyvind. Thank you! That guy in your second link is a mate of mine! I have to defer on how air could have come in. I can only think of two scenario's: a small leak, draining the reservoir. The car should have warned you way way way before the reservoir was empty though. The second is that the booster servo creating an under-pressure in it's suction line. You might want to now and then brake with the gear in N, so full hydraulic braking. If the pedal feels "spongy" instead of hard, that is a sign of air. But as said, I don't feel confident to give any advice. I hope you can still enjoy your Zoe!

By: Oyvind

Oyvind — Sat, 11 Jun 2016 20:36:29 +0000

Internet search revile that similar happenings seems to have been reported. One said also after 5K km use. Is it two independent hydraulic systems? Perhaps there is a leakage where air enters? The shop said they did not know what could cause this situation. Well, have to hope it does not happened again. And, thanks for the link to the information/documentation.
If you intend to take your Zoe on a visit to Norway, her is some info.: http://elbil.no/elbilforeningen/english-please/3801-the-ultimate-tourist-guide-for-ev-driving-in-norway
And this one: http://elbil.no/nyheter/elbilpolitikk/3617-from-holland-to-geiranger-in-his-renault-zoe

By: Jeroen Meijer

Jeroen Meijer — Fri, 10 Jun 2016 12:39:07 +0000

In reply to Oyvind.

Seems my hunch was right then? And that’s about the only positive thing that can be said I guess.

An air bubble in the hydraulics is a very, very bad thing. No car can handle that well, though front and back should be independent. AFAIK (but you’ve noticed my disclaimer earlier) it can only occur with a bad oil type or a wrongly executed (re)fill. The procedure for the Zoe I have not seen, only referred to, but I know it is complicated and cannot be done without the CLIP diagnostic system hooked up. It’s not like the old days with your rosted 2CV 😉

By: Oyvind

Oyvind — Fri, 10 Jun 2016 10:32:13 +0000

The R240 returned after also tech. people from R/France have worked on it, now says it is function and R240 is safe. They said many error code was read from the car, however state only C023. Said no parts were replaced. Said there were air bubbles in the braking system. How does bubbles appear after 1/2 year, and how does the reset procedure (second run) reset braking function? Are the braking computers (software, hardware, sensors) really robust enough in such a bubble situation?

By: Jeroen Meijer

Jeroen Meijer — Sun, 05 Jun 2016 19:42:38 +0000

In reply to Oyvind.

If the car didn’t brake at all (meaning it also didn’t when fully pressing the pedal, so un-assisted), that would be a very serious failure mode. If it were my car I would insist on a printout of the failure codes and descriptions as proof, and an answer from Renault Service in your country. At this moment, I can only imagine an air bubble in the hydraulics, but that’s probably my fantasy failing on me!

DISCLAIMER: I am not a car mechanic, nor involved with Renault. I am a guy interested in technology who happens to drive a Zoe.

By: Oyvind

Oyvind — Sun, 05 Jun 2016 19:03:55 +0000

The R240 had run 5k km when brakes failed. Brake failure indicator on dash. Speed less than 30. Stopped by using parking brake. Called R service which suggested. Did reset procedure. Start the car but brakes do not function. Do reset procedure second time and brake works. Brake do function the 20 km to Renault service. They could read brake failure information in the car diagnostic system. The car is still at service.

By: Jeroen Meijer

Jeroen Meijer — Tue, 31 May 2016 07:24:00 +0000

In reply to Oyvind.

No, it doesn’t work like that. In case of a failure, the backup is entirely hydraulic, using the drivers pushing force. I really think you should read this http://www.scribd.com/doc/256077973/Renault-Zoe-2013-pdf document, which I referred to in my post.

Would you be so kind to substantiate the no-braking rumours?

By: Oyvind

Oyvind — Tue, 31 May 2016 05:22:27 +0000

Is there a diagram/documentation available showing where the sensors controlling the brake pedal movement are, is there more than one computer controlling the friction brake? If the only one computer that is controlling the braking, including the friction braking, is failing, than I presume the Zoe has a total braking failure? Is there available a detailed description of the braking system where it is describing failure scenarios and then the possibility of total robustness or no-robustness?

By: Jeroen Meijer

Jeroen Meijer — Mon, 30 May 2016 21:45:12 +0000

In reply to Oyvind.

The design seems pretty robust (at least as robust as a conventional vacuum or servo powered braking system), with the added torque of the motor. I am not dismissing your observation “just because”, but would such a car even be certified for the road nowadays? Unless of course it was a double failure (failure of the backup system), but then all bets are off.

I would be truly interested in a trustworthy account and how his could have technically happened!