backyak Posted May 20, 2019 Report Share Posted May 20, 2019 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! Quote Link to comment Share on other sites More sharing options...
grege Posted May 21, 2019 Report Share Posted May 21, 2019 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! Our 2017 and 2018 make "normal" brake noises, although some odd ones at times. Best would be posting a video WITH audio of yours to compare.Greg backyak 1 Quote Link to comment Share on other sites More sharing options...
jestevens Posted May 21, 2019 Report Share Posted May 21, 2019 (edited) There are two different braking systems in the car - regenerative braking that turns motive energy back into electrical energy stored in the high voltage battery and traditional hydraulic brakes if more stopping power is needed. I think this car is "brake by wire" - there is no direct connection between the brake pedal and the hydraulic system - the pedal sensor only tells the computer how much force you are applying and then the computer can decide what mix of regenerative and hydraulic braking to apply to charge the battery and/or stop in emergency. The C-MAX and Prius seem make a hiss/buzz/whir noise while replenishing the brake accumulator, that part is probably normal but I've never heard a "hop hop". You could test drive another C-MAX to see if it makes a similar noise? Edited May 21, 2019 by jestevens Quote Link to comment Share on other sites More sharing options...
plus 3 golfer Posted May 21, 2019 Report Share Posted May 21, 2019 (edited) There are two different braking systems in the car - regenerative braking that turns motive energy back into electrical energy stored in the high voltage battery and traditional hydraulic brakes if more stopping power is needed. I think this car is "brake by wire" - there is no direct connection between the brake pedal and the hydraulic system - the pedal sensor only tells the computer how much force you are applying and then the computer can decide what mix of regenerative and hydraulic braking to apply to charge the battery and/or stop in emergency. The C-MAX and Prius seem make a hiss/buzz/whir noise while replenishing the brake accumulator, that part is probably normal but I've never heard a "hop hop". You could test drive another C-MAX to see if it makes a similar noise?Not quite, if the brake pedal is pushed far enough, the brake booster push rod is forced into the master cylinder and conventional friction braking occurs. Brake by wire is a necessity for EVs, PHEVs, and HEVs for regenerative braking purposes. But, I doubt there is any brake by wire system that does not have a mechanical link from the brake pedal to the master cylinder for safety. One can look up the NHTSA Standards and Rules that apply to braking and see what is required. Here's a snip on the how this is implemented in the C-Max. Edited May 21, 2019 by Plus 3 Golfer jestevens 1 Quote Link to comment Share on other sites More sharing options...
plus 3 golfer Posted May 21, 2019 Report Share Posted May 21, 2019 (edited) With respect to the brake noise, OP, try posting question on the C-Max Energi Forum also and even the Fusion Energi Forum. Noise from the ABS is considered normal as a vacuum pump motor, fluid pump motor, and booster solenoid will be operated. Did the dealer scan for Diagnostic Trouble Codes? The ABS is considered a part of the OBDII monitoring because it controls regenerative braking which affects FE. If dealer found no faults, the noises are likely normal. So, are you holding the brake pedal all the way and the noise repeats every 10 seconds? If so, that could be the operation of the electric hydraulic brake fluid pump by the ABS module. I don't know the frequency of testing / monitoring to detect faults. What happens when you take your foot off the brake? no noise? How far are you pushing the pedal if not holding it in? and is the noise still there if not all the way in? There is the brake booster solenoid (see snip in above post) that will open to allow vacuum to draw the booster diaphragm and push rod towards the master cylinder piston, building hydraulic pressure. Air will rush in on the other side of the booster diaphragm. Edited May 21, 2019 by Plus 3 Golfer Quote Link to comment Share on other sites More sharing options...
backyak Posted May 22, 2019 Author Report Share Posted May 22, 2019 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! Quote Link to comment Share on other sites More sharing options...
plus 3 golfer Posted May 22, 2019 Report Share Posted May 22, 2019 That thumping doesn’t sound normal to me. I’ve never heard it with foot on brake.I’ll look again at the manual for any tests that might be done continuously that might have a frequency of a few seconds. Maybe the solenoid valve is operating on / off and the push rod is being drawn into the master cylinder or the fluid pump is kicking on / off. Another potential use for the FORScan App to look at ABS data. There are other valves that control the pressure to the front / back brakes, dump valves and so forth. Dealer won’t do anything without a DTC showing. Quote Link to comment Share on other sites More sharing options...
plus 3 golfer Posted May 22, 2019 Report Share Posted May 22, 2019 Maybe try activating the ABS by driving at 40 mph and slamming on the brakes and see if a DTC is thrown, (CEL) or message pop up. Quote Link to comment Share on other sites More sharing options...
backyak Posted May 22, 2019 Author Report Share Posted May 22, 2019 (edited) 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... Edited May 22, 2019 by backyak Quote Link to comment Share on other sites More sharing options...
grege Posted May 22, 2019 Report Share Posted May 22, 2019 Backyack, Nice job loading video and sound. I agree with Plus3 with respect to the thumping sounding unusual; doesn't mean it's bad necessarily, but don't recall either of ours sounding like that, although I do notice my wife's brake pedal often "thumps" when taking your foot off it while mine will not. I will pay more attention the next few trips I make and let you know if mine sound similar to yours. If it bothers you enough, try one more dealer to gauge their findings. Cars today a lot more "odd" sounds than ever. Greg Quote Link to comment Share on other sites More sharing options...
backyak Posted May 23, 2019 Author Report Share Posted May 23, 2019 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. Quote Link to comment Share on other sites More sharing options...
plus 3 golfer Posted May 23, 2019 Report Share Posted May 23, 2019 Because ICE may not be running all the time, there is a electronic vacuum pump which is the primary source of vacuum for the ABS. If it fails, the backup would be ICE vacuum, and software would keep ICE running in that event. Look at the attached pdf starting at page 180 on the ABS. If you don't have a DTC (vacuum low, vacuum leak detection), it's hard to justify replacing parts with the hope it fixes the noise. I've found the best way to use FORScan is to record data and then analyze the data via a spreadsheet comparing data when the issue (noise, brake pedal in) is present and not present. You could also record engine data when starting car and do the same comparing rough idle condition with normal condition. How many miles on your car? "Vacuum level sensors are used to monitor the vacuum being provided by the engine and vacuum pump, and isused to control the state of the electric vacuum pump. Failure modes sensed and detected include vacuum supplylow, and vacuum leak detection." OBDSM1503_HEV.pdf Quote Link to comment Share on other sites More sharing options...
backyak Posted May 23, 2019 Author Report Share Posted May 23, 2019 Hi, Plus 3Thanks 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. Quote Link to comment Share on other sites More sharing options...
plus 3 golfer Posted May 23, 2019 Report Share Posted May 23, 2019 Oops I attached the 2015 document not the 2017 which is attached below. OBDSM1700_HEV.pdf Quote Link to comment Share on other sites More sharing options...
grege Posted May 23, 2019 Report Share Posted May 23, 2019 Tested it on mine and while it makes the constant electrical pump or "whine" sound when depressing the brake pedal, it does not make the rhythmic thumping sound. Greg Quote Link to comment Share on other sites More sharing options...
backyak Posted May 23, 2019 Author Report Share Posted May 23, 2019 Greg, Thanks for your confirmation! Quote Link to comment Share on other sites More sharing options...
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