Parking brake not releasing quick enough

[JodyS21]

Has anyone else had this occur?

Today, waiting at a busy junction, was at a complete stop so the auto brake (green P) was holding the car, had to pull out quickly (was in E3), so put my foot flat to the floor.
I was expecting a bit of wheel spin - especially as I was turning right so had the wheel turned.
The car took off with a clunk noise (and a bit of wheel spin), then after straightening up and going I could smell a brake burning smell (the smell went within about 30secs).

I think the car had engaged all the power to the motor/wheels before it had (completely?) disengaged the holding brake.
Given it’s all electronically controlled I thought the car would ensure then appropriate process was followed I.e. issuing brake release command, pause for the necessary number of milliseconds, before applying power to the motor.

 

[Jomarkh]

Hi,
My MG5 is a bit slow on releasing the green p i wonder if it was in Sports mode it would release quicker

 

[SCB86]

Sometimes when I'm reversing the parking brake doesn't disengage at all and it locks the back wheels and skids backwards. I have to press park and select drive again before it will release.

 

[Deleted member 823]

was at a complete stop so the auto brake (green P) was holding the car, had

Can you clarify what you mean please? It might be me being daft and not having had enough coffee yet...

 

[Gomev]

Autohold, the button next to the Parking Brake button in front of the drinks holder (centre column).

When activated automatically applies the handbrake when you have braked to a complete standstill and releases when you apply pressure to the Go pedal.

From the manual
If the vehicle is required to stop frequently for a length of
time (such as traffic lights, traffic queues or stop/start), and
the power system is running, the auto hold system assists
in stabilising the vehicle, enabling you to remove your foot
from the brake pedal when the vehicle is stationary and the
Auto Hold active.
Auto hold has 3 main states:
1 Off: Function in Off state.
2 Standby: Function in Standby state. The function is
active but the vehicle has not stopped. Once the
vehicle has stopped, and all other conditions are met,
the system will automatically select Park.
3 Parking: Function in Parked state. In this state the
green indicator on the instrument pack illuminates.

With the driver's seat belt fastened, the door closed and
the power system operating, press the auto hold switch to
switch the auto hold function from Off to Standby state.
With the brake pedal firmly pressed and the vehicle
completely stopped, the auto hold function will switch
from the Standby state to the Parking state.

 

[Cocijo]

If you are at standstill with the auto hold engaged (green p) , after about 2 mins the parking brake engages (red p). I think auto hold and the parking brake engage different systems.

 

[Kithmo]

This is one of the reasons I don't use Auto hold, too clunky for my liking. Hill start assist is much more useful and smooth.

 

[JodyS21]

This is one of the reasons I don't use Auto hold, too clunky for my liking. Hill start assist is much more useful and smooth.

Hill start assist is switched on/off via the touch screen isn’t it?
How does it differ/how is it used?

 

[Mike]

Hill start assist is switched on/off via the touch screen isn’t it?
How does it differ/how is it used?

That’s Hill Descent. Hill start is when you stop on an incline without auto hold the car will stay still for a few seconds before it starts to roll backwards down the hill.

 

[JodyS21]

This is one of the reasons I don't use Auto hold, too clunky for my liking. Hill start assist is much more useful and smooth.

So to confirm, you have the auto hold switch off; you keep your foot on the brake pedal until you want to pull off, the hill start assist stops the car from rolling whilst you’re moving your foot from the brake to accelerator pedal?
Is Hill start assist permanently on?

 

[Mike]

So to confirm, you have the auto hold switch off; you keep your foot on the brake pedal until you want to pull off, the hill start assist stops the car from rolling whilst you’re moving your foot from the brake to accelerator pedal?
Is Hill start assist permanently on?

Yes

 

[Gomev]

Yes

What @Mike said.

from the manual

Hill Hold Control is a comfort function. It works on
inclines when the car detects it has come to a ‘stand still
status’. As long as D or R is selected and the brake pedal
released, the vehicle will maintain pressure in the braking
system for 1 – 2 seconds. After this, the Hill Hold will
release.
HHC assists the driver by 'holding' the vehicle during hill
starts.
The following conditions must be fulfilled to activate HHC:
• The driver's door is closed and the driver seat belt is
fastened.
• The vehicle is stopped on a slope in excess of 4% and
for more than 2 seconds.
• SCS is active and fault free.
• EPB is released and fault free.
• In D or R gear.
• Power system is READY/RUNNING.
• Sufficient brake pedal application force has been applied.
If the driver releases the brake pedal on a hill, HHC will
maintain brake pressure for 1 - 2 seconds, after this period
the vehicle may roll backwards.

 

[Kithmo]

When it says, "Sufficient brake pedal application force has been applied" it means press the brake pedal hard before releasing it (the same as on my old Prius), otherwise it might still roll.
I can confirm it works in reverse too, very handy when you've parked nose in close to a wall etc. on a downward slope.

 

[Deleted member 823]

That auto hold as described by @Gomev doesn't apply the brakes, does it? I can't hear anything engage. My usual practice when stopping (at lights, in traffic, junctions, etc.) is to just tap the silver selector disc, then select D/pressing the brake pedal when moving off. Using the auto hold illuminates a green parking brake light in the dash, but I can't hear the brakes engage as you would when using the handbrake button or manually selecting P.

 

[SCB86]

Auto hold holds the brake pressure when you come to a stop, so it doesn't engage the handbrake (until auto hold has been active for too long and then it engages the handbrake)

 

[Gomev]

That auto hold as described by @Gomev doesn't apply the brakes, does it? I can't hear anything engage. My usual practice when stopping (at lights, in traffic, junctions, etc.) is to just tap the silver selector disc, then select D/pressing the brake pedal when moving off. Using the auto hold illuminates a green parking brake light in the dash, but I can't hear the brakes engage as you would when using the handbrake button or manually selecting P.

I almost never use the 'P' on the gear selector unless I am Parking.

In an automatic ICE would you select Park at traffic lights or junctions ?

 

[JodyS21]

I almost never use the 'P' on the gear selector unless I am Parking.

In an automatic ICE would you select Park at traffic lights or junctions ?

Same here.
I have an auto ICE too, very rarely use park unless my foot is aching after a very long pause.

From a racing background though, I don’t like to keep the front brakes engaged for too long when unnecessary/stopped. But unless you’re hammering the brakes so they’re really hot, which rarely happens - especially in an EV, it’s not an issue.

 

[Deleted member 823]

I almost never use the 'P' on the gear selector unless I am Parking.

In an automatic ICE would you select Park at traffic lights or junctions ?

It works for me, whatever others do is up to them.

A related question though for everyone - if using auto hold, as I understand it from this thread, this applies the brakes (excluding the handbrake) whilst the car is in D. Are there any concerns about effectively having it in D - i.e. the car is wanting to move forward and stopping this with the breaks? I too have driven auto recently, and based on a mechanic friend's advice from many years ago, never repeated this whilst stopped.

Also, whilst out yesterday, I tried messing with MG Pilot in traffic, something I've been wary of doing as it seems to approach very closely to the car in front before stopping. I found that hen moving again on an upward incline, the car will roll backwards without driver intervention!

 

[JodyS21]

It works for me, whatever others do is up to them.

A related question though for everyone - if using auto hold, as I understand it from this thread, this applies the brakes (excluding the handbrake) whilst the car is in D. Are there any concerns about effectively having it in D - i.e. the car is wanting to move forward and stopping this with the breaks? I too have driven auto recently, and based on a mechanic friend's advice from many years ago, never repeated this whilst stopped.

Also, whilst out yesterday, I tried messing with MG Pilot in traffic, something I've been wary of doing as it seems to approach very closely to the car in front before stopping. I found that hen moving again on an upward incline, the car will roll backwards without driver intervention!

Interesting, not sure what it really does on an auto and if it’s true it could cause an issue - you’d think it’d engage the clutch.
Definitely shouldn’t be an issue on an EV as the electronics should fully handle it and not engage any power whilst the brakes are engaged.

Does MG pilot take any notice of the ACC distance setting up the car infront? I sometimes use the lane keeping functionality but never turn on full MG pilot. That’s not good if it rolls backwards a bit!!!

 

[macd2401]

A related question though for everyone - if using auto hold, as I understand it from this thread, this applies the brakes (excluding the handbrake) whilst the car is in D. Are there any concerns about effectively having it in D - i.e. the car is wanting to move forward and stopping this with the breaks? I too have driven auto recently, and based on a mechanic friend's advice from many years ago, never repeated this whilst stopped.

Pretty sure when auto hold comes on, the electric supply to the motor stops. Check your current flow next time you're out.

One reason I would agree, and use park at junctions/lights etc, is that I'm pretty sure auto hold keeps the brake lights on, and that's wearing to anyone stopped behind, more so at night, and especially if you've got led bulbs.