Mild jerking/pulsing at motorway speeds W164 2010 ML350 D,

[daimlerbenzman]

Hello

The car is an ML350, serviced regularly. Note, I've changed the rear brake callipers and discs, as the off side rear had over heated and the calliper cracked for some reason.

I've been experiencing this jerking issue consistently from around 30MPH upwards, more noticeable on the motorway because it stands out when you're holding a steady speed

Its very very annoying and spoils the driving experience even on short trips. additional info

• 80000 miles on the clock
• steering is smooth but sometime some of the jerking can be felt
• the revs stay smooth and consistent, ie the needle does not jerk
• my guess would be 1 - 2 jerks/pulses per second
• it may be engine, drivetrain or even something around the hub (previously I noticed excessive heat and discovered a broken calliper

Any help is welcome, thank you

 

[Smart320]

I wonder if it could be the ABS pulsing on and off ? As you have been working on the rear brakes I would guess it is much more likely to be brake related than engine or drivetrain, perhaps something not right with the ABS Sensors / fitting . Am not an expert but am sure there will be other forum members along soon who will give you a more technical response regarding possible causes.

 

[daimlerbenzman]

That’s such a good thought. I’m compiling a small list of things to investigate

I currently check the temp of the hubs with my hand after a long journey, because I was so suspicious of the off side rear (the heat was obvious), it turned out to be a broken calliper but the ABS could be a factor.

 

[Petrol Pete]

A cracked brake caliper ? Thats rare. Where about on the caliper was the crack ? were pads/pins fitted incorrectly ?

 

[Trickythemerc]

I had something quite similar on my CLK. turned out that the hose clip on the air box side of the turbo had broken allowing the hose to work loose. When it did finally throw a code it pointed towards nox sensor..? On inspection I spotted the shiny end of the turbo and the broken clip, replaced it and all good again.

 

[m80]

I had a very occassional feeling of drag,only noticable while motorway cruising.
Driving a Vito I thought it might have been side wind.
An ABS sensor threw its hand in, now replaced and the accasional feeling of drag has gone.
I guess on it's way out it caused the cruise to hesitate.

 

[daimlerbenzman]

A cracked brake caliper ? Thats rare. Where about on the caliper was the crack ? were pads/pins fitted incorrectly ?

Hi. I didn't see the calliper myself. I dropped the car to a small neighbourhood garage near where some family live, and the chap there found it - I'm starting to think the ABS should be checked, though there were no errors when I got diagnostics done recently...

PS. I got three diagnostic checks done recently, because a big power loss issue could not be found. First by the main dealer, then two specialists. Then the power problem went away

 

[daimlerbenzman]

I had something quite similar on my CLK. turned out that the hose clip on the air box side of the turbo had broken allowing the hose to work loose. When it did finally throw a code it pointed towards nox sensor..? On inspection I spotted the shiny end of the turbo and the broken clip, replaced it and all good again.

Thank you! I'm definitely going to investigate this. Sounds like a good thing to check out anyway

 

[daimlerbenzman]

I had a very occassional feeling of drag,only noticable while motorway cruising.
Driving a Vito I thought it might have been side wind.
An ABS sensor threw its hand in, now replaced and the accasional feeling of drag has gone.
I guess on it's way out it caused the cruise to hesitate.

Thank you. I definitely asked in the right forum! I'm going to investigate this. I do a lot of miles and spend a fair bit of time in the car so checking the ABS sensors is a good idea, thank you

 

[daimlerbenzman]

I wonder if it could be the ABS pulsing on and off ? As you have been working on the rear brakes I would guess it is much more likely to be brake related than engine or drivetrain, perhaps something not right with the ABS Sensors / fitting . Am not an expert but am sure there will be other forum members along soon who will give you a more technical response regarding possible causes.

Thank you. I share the feeling that brakes is a good place to focus first. I will let you know how the ABS check goes

 

[megaguru]

yes do let us know when and what was cause it be interesting