backyak

Greg, Thanks for your confirmation!

Hi, Plus 3 Thanks again for your kind response. The attachment is extremely helpful. I'll read it very carefully. If there is a vacuum sensor for break, I think my car doesn't have any mechanical problem. I tried ABS (hard stop) more than 10 times today and checked FORscan at each try. There was no issue and break worked perfectly. Also, engine is not turned on while breaking. It would be another evidence that vacuum system is okay. (The noise occurred at both ICE and EV modes.) My car is about 11,000 miles and I've leased it since Dec 2017 (ends this winter). I think I'll keep this one as I love this car but only if this noise is not a serious issue. Currently, nobody knows where it comes from, which is what I want to know at first. :D For being sure, I'll visit another Dealer asap. But, I agree with you that dealer won’t do anything without a DTC showing. If I find the answer, I'll write up the details for everyone's information.

BTW, According to the diagram attached by Plus 3, C-MAX's brake booster is just behind the brake pedal, and brake booster, master cylinder and pedal are all combined? Does C-MAX brake booster has a link to the ICE for vacuum? If so, how to make vacuum when ICE is turned off? I sometimes have a rough engine at idle (while warming up the engine at cold start), and I thought it might be related with a vacuum leak at break booster. But if they are not linked, my thought is completely wrong. Is it difficult to replace the brake booster? To be honest, I don't want to replace anything as my C-MAX is still under 12,000 mile so relatively new.

I have OBD so can easily check the ABS data. I just have done it. FORScan doesn't show any error message at ABS. One error appeared at Accessory Protocol Interface Module - Invalid Dat Received from Body Control Module. How about the vacuum leak at brake booster? The ABS has never activated in my car as my braking is always very smooth. I'll check it. Thanks for your suggestion. I'm happy to know that you don't have this issue...

Grege, Jestevens, Plus 3 golfer, Many thanks for your answers. I don't know how to upload movie file at this site, so uploaded it to youtube. https://youtu.be/VKWMr0g6s7o Today, I visited Dealer once again and got a response. Of coarse, they say it is normal operating noise. Mechanic and I checked other cars, 2016 CMAX energi and 2019 Fusion energi. Both of them doesn't have this sound. But, still, they think it is normal operating noise and don't know where it comes from. If I release the pedal, the noise goes away. Whenever I press the pedal at full stop, it makes sound. Do you have any suggestion? As brake is fully functional, I don't worry too much but need to understand where it comes from. Have a nice evening!

Hi all, I have C-max Energi SE 2017, and I have annoying noise at a full stop. I wonder if you have the same issue as Dealer says it is normal operation noise. Below is the symptom. At a full stop (even just after turning on my car), while pressing the brake pedal, I can hear "hop, hop" noise every 10 secs — the interval and level of noise changes. It starts with electronic noise "W---- wing" then begin to "hop, hop". The noise comes from the brake pedal or nearby. The noise seems like an air leak. Do anybody has a same noise? Many thanks for your kind answers!