Driving Downhill on Cruise Control
Thread Starter
Member
Joined: Oct 2024
Posts: 173
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From: California
2016 E350 Sport
Driving Downhill on Cruise Control
Yesterday, I was driving downhill on a steep grade, and put car on cruise control at 65 MPH. As I nearly reached the end of that slope, I could feel car struggling to keep the braking consistency which was followed by what sounded like slight vibration and noise coming from the rear end. I immediately stepped on brakes to disengage cruise control, which immediately ended the noise and vibration. I'm starting to think this was a rear brake shoes issue, especially with me having had them adjusted a week ago to address the parking brakes not engaging when parked on an incline, which didn't solve that problem. I have an appt with dealer who installed new parking brake mechanism this coming weekend. What do you think could explain the type of noise and vibration I had coming down that steep grade?
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
SERVICE BRAKES SOON...
Yesterday, I was driving downhill on a steep grade, and put car on cruise control at 65 MPH. As I nearly reached the end of that slope, I could feel car struggling to keep the braking consistency which was followed by what sounded like slight vibration and noise coming from the rear end. I immediately stepped on brakes to disengage cruise control, which immediately ended the noise and vibration. I'm starting to think this was a rear brake shoes issue, especially with me having had them adjusted a week ago to address the parking brakes not engaging when parked on an incline, which didn't solve that problem. I have an appt with dealer who installed new parking brake mechanism this coming weekend.
What do you think could explain the type of noise and vibration I had coming down that steep grade?
What do you think could explain the type of noise and vibration I had coming down that steep grade?
>> The top answer is: Warped Brake Rotors. Brakes have many more ways to vibrate including loose suspensions.
Get your brakes serviced during MB dealer visit for best results.
> You can have a quick look at where brake fluid level stands in MC reservoir.
It directly reflects brake pad wear.
> The other quick tip is post 4x picture of your wheels/brake rotors... this should show how your brakes are working (color ; grooves ; smoothness)
Last edited by CaliBenzDriver; Jan 6, 2025 at 05:29 PM.
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From: In the Shadow of the Tetons
2013 ML350 Bluetec
Long downhill counting on the brakes to keep a set speed? Ya, you overheated things. Maybe next time do a downshift for a gear or two, even with the cruise control engaged. Let the engine do what it's meant to do and save your brakes for stop signs.
Thread Starter
Member
Joined: Oct 2024
Posts: 173
Likes: 62
From: California
2016 E350 Sport
FYI: rear brake shoes stay inactive while driving.
>> The top answer is: Warped Brake Rotors. Brakes have many more ways to vibrate including loose suspensions.
Get your brakes serviced during MB dealer visit for best results.
> You can have a quick look at where brake fluid level stands in MC reservoir.
It directly reflects brake pad wear.
> The other quick tip is post 4x picture of your wheels/brake rotors... this should show how your brakes are working (color ; grooves ; smoothness)
>> The top answer is: Warped Brake Rotors. Brakes have many more ways to vibrate including loose suspensions.
Get your brakes serviced during MB dealer visit for best results.
> You can have a quick look at where brake fluid level stands in MC reservoir.
It directly reflects brake pad wear.
> The other quick tip is post 4x picture of your wheels/brake rotors... this should show how your brakes are working (color ; grooves ; smoothness)
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From: KY
2015 E63S Sedan, 2014 E550 coupe
@CaliBenzDriver I thought I read somewhere that Distronic+ activation utilizes rear brakes to modulate speed…no?
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19 GLA45, 86 560SL, former: 14 E550 4Matic, 09 E350 4Matic, 83 240D manual, 78 450SLC, 81 500SLC
@CaliBenzDriver I thought I read somewhere that Distronic+ activation utilizes rear brakes to modulate speed…no?
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
@CaliBenzDriver I thought I read somewhere that Distronic+ activation utilizes rear brakes to modulate speed…no?
It's a lot if fun in stop and go traffic-crawl
The odd braking is Lane Keeping Assist and Blind Spot Assist moves car over like 1Ft using one side only.
So individual brakes don't wear out evenly.
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From: Phoenix, AZ
2016 E350 Sport 2WD
I recently had 2 occasions where my car (2016 E350 Sport RWD) had what I think might be the same braking problem. Both were long downgrades in cool (50's) weather, one from Flagstaff to Phoenix on I-17 and the other from Payson to Phoenix on US 87 with Distronic on and controlling the speed. It felt like a rapid, noisy braking application and I thought it felt like it came from the rear. After I shut off Distronic, I applied the foot brake and the braking sensation was the same for a few minutes. I decided that the brakes were hot and geared down to give the brakes time to cool. A few minutes later, the sensation ceased both for manual braking and speed-controlled Distronic braking. I have looked at my rotors and pads and see nothing that would explain the braking sensation. I expected that I would see some heat spots or irregularities on the discs, but nothing.
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1922 Ford Model T / no OBD
CC on steep downhill activates "hill descent" mode, who will try to slow down the vehicle by engine braking and downshifting.
My diesels do have fins on turbo, who also act as exhaust brake and I can feel braking power when I don't think it ever applied wheel brakes.
Might be different on gasoline engines without exhaust brake.
Either way, reading the manual might be good idea.
My diesels do have fins on turbo, who also act as exhaust brake and I can feel braking power when I don't think it ever applied wheel brakes.
Might be different on gasoline engines without exhaust brake.
Either way, reading the manual might be good idea.
Senior Member
Joined: Apr 2016
Posts: 457
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From: Phoenix, AZ
2016 E350 Sport 2WD
Thanks for your thoughts. I've descended these hills many, many times, and the results were markedly different this year. And I note that even after CC was turned off, the problem continued for a short time, even with manual braking. I don't think the user manual will explain that.
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Joined: Mar 2024
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From: Chicago
19 GLA45, 86 560SL, former: 14 E550 4Matic, 09 E350 4Matic, 83 240D manual, 78 450SLC, 81 500SLC
CC on steep downhill activates "hill descent" mode, who will try to slow down the vehicle by engine braking and downshifting.
My diesels do have fins on turbo, who also act as exhaust brake and I can feel braking power when I don't think it ever applied wheel brakes.
Might be different on gasoline engines without exhaust brake.
Either way, reading the manual might be good idea.
My diesels do have fins on turbo, who also act as exhaust brake and I can feel braking power when I don't think it ever applied wheel brakes.
Might be different on gasoline engines without exhaust brake.
Either way, reading the manual might be good idea.
Though my 240D did have a little butterfly valve in the intake path which I think was added just to give some engine braking, but somehow it didn't have much effect. That engine redlined at 4xxx RPM though....
