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Noise from standstill

Most likely brake related, possibly the parking brake not fully disengaging.
I would also point to the parking brake as the unwinding of parking brake calipers is suspiciously too long. And you will not see that hold indicator on IC if you do not let the brake pedal free. That hold is always used on parking brake so it’s there even if you come to a stop on any traffic light. That permanent magnet motor function is only available for FSD and is fully electric, meaning the standstill is performed by motors, not by the brakes. Have you checked the pads on parking brake, yours should be separate calipers?
 
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wk057

Vendor & Senior Tinkerer
Feb 23, 2014
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14,856
Hickory, NC, USA
And you will not see that hold indicator on IC if you do not let the brake pedal free. That hold is always used on parking brake so it’s there even if you come to a stop on any traffic light. That permanent magnet motor function is only available for FSD and is fully electric, meaning the standstill is performed by motors, not by the brakes.

This is quite incorrect.

The parking brake is only used for the park "gear". In cars up to about 2018, this was a separate caliper with an electric gear to engage and disengage a separate set of brake pads on the rear wheels to use as a parking brake. Later, this was integrated into the rear hydraulic brake calipers which have an electric system for actuating the rear hydraulic calipers to double them as a parking brake. Regardless of model/type, the parking brake system has never been used for any other purpose other than when the car is put into park.

The hold/standstill function, on AP1 and newer vehicle (Q4'14+), is done using the iBooster electromechanical braking system that controls the hydraulic brakes of the entire car. This is how autopilot/FSD is able to control braking at all in the first place. The hill hold system just commands the iBooster to maintain hydraulic brake pressure to keep all of the brakes at whatever pressure was originally commanded.

Never vehicles have an updated version of the iBooster/ABS system that gives finer control (about 2018+), which is how they're able to do the newer regen/brake blending thing, as well as the driving mode that allows completely one-pedal driving. This is all done with the hydraulic braking system via the iBooster. The parking brake is never used for these functions.

This is quite obvious when using any of these car-controlled-braking setups, because the physical brake pedal actual moves as the iBooster is commanded to different levels of braking. Tesla even includes a warning with the new regen/brake blending that the brake pedal will feel different when using it, since it will be already partly engaged during this faux regen deceleration.

The traction motors are never used to hold the vehicle at a stop, in any variant. This would not only be bad for the motor and power electronics, it would be ridiculously wasteful on the energy front. Holding the car in place on a hill using the powertrain requires generating sufficient energy continuously at the wheels to basically counter gravity's effect of trying to move the car down the hill. The car would have to put in at least that much energy to hold the car still, and this would all just be lost as heat in the powertrain as it strains the motors to perform this task. Instead, more sanely, the car just uses the hydraulic brakes to lock the wheels in place and tells gravity, "Look, you're fight is with friction now. I'm out." 😁

On pre-AP1 vehicles, there is still a hill hold function that activates upon a full brake pedal press when on an incline above a threshold. Since pre-AP1 cars don't have an electronic braking system and instead use a classic vacuum assisted braking setup, this hill hold function is handled by actuating the ABS system's hydraulic pump and valves in a clever way that delays the release of hydraulic pressure from the brakes for about a full second. This pretty much just gives you sufficient time to move your foot from the brake to the accelerator without risking rolling backwards.

I'm not sure where people get the misinformation, like quoted above, but hopefully this clears up how these things work.
 
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It was just my humble assumption and my understanding about how the hold of brakes work. I had always thougt that the non-movement was done by parking brake as you are releasing the main brakes. I thank you for your clarification and long explanation. My assumption about the hold and the braking functions during Autosteer was mainly gathered from the internet and about the claims that auto stopping was never possible (software side) without the new permanent magnet motors that came soon after Model 3 appared. So apologies for misleading and thanks for the great support you are providing.
 
Have you checked the pads on parking brake, yours should be separate calipers?

Just did a visual check without removing the tires:
Parking break passenger rear Driver rear

Parking Rear Passenger.jpg
Parking Rear Driver.jpg



I went ahead and ordered new parking brake pads, I figured it wouldn't hurt to change them out.

Regular brake pads seemed to be still good with pad wear:

Driver Front.jpeg
Passenger Rear.jpeg
Driver Rear.jpeg
Passenger Front.jpeg


Sorry about the formatting of the pictures, due to the way the cell phone was positioned to get a decent pictures.
 
Some additional information as I took car out for another run. I wanted to see if I could notice the noise or feel something happening without coming to a full stop to rule out the brakes being part of the issue. I noticed a subtle noise and felt something give when letting go (might be normal when lifting off the accelerator) of the accelerator. I pressed the allelotor again without touching the brake pedal at all. I noticed the same noise but it was very subtle and felt like something engaging. This almost tells me since the noise is still happening without the brakes being engaged at all, it might be a linkage issue either having a slack or just being loose. Of course this could just be my wild guess.
 
I forgot to mention that I've noticed when braking I was hearing the brakes squeal like the pad was worn down, I'm sorry I had forgotten to mention that before (must my old forgettable mind again). This happened for a couple of days regularly when applying the brakes, and then disappeared. It came back once on yesterday's drive and that's how I remembered that I had forgotten to mention it here. It's odd that there was this brake squeal though as the regular brake pads seem to have a decent amount of pad left on them at least on one side and I would hope it to be the same on the other side. The original noise issue was still present when the accelerator was pressed though.

I also noticed that first time I move the car for the day, for example this morning I moved the car back and forth for a travel of about 4 feets twice back and twice forward and it didn't make any noise. On the fifth movement going forward it made the original noise (clunk). Its like something needed more use to not make that noise until it was used for a bit.
 
Thing I noticed is that the thump noise does seem to happen even when lifting the foot off the accelerator. The noise isn't as strong though when pressing the accelerator, so I think that might rule out the brakes being the issue. It feels as though something has slack or is loose and when the accelerator is pressed or unpressed this thump comes into question. I've opted for the diagnosis and will update once SC has looked at it on the 16th.
 
Just wanted to provide an update, finally got the car to SC after original appointment was re-reschedule. Dropped the car over at SC yesterday, they looked at it and adjusted the estimate today to reflect that it needs an replacement of LDU and rear half shaft. I had inspected the speed sensor and didn’t notice any sign of moisture. Are the rear half drive and LDU one unit or separate? I’m also inquiring thru the chat to ask which one is the cause of the original noise as well. Just wanted to share in case if others heard similar noise from rear drive area when moving from standstill position.
 
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NewbyMaybe

Newby1Kenowby
May 3, 2021
543
176
Florida
Just wanted to provide an update, finally got the car to SC after original appointment was re-reschedule. Dropped the car over at SC yesterday, they looked at it and adjusted the estimate today to reflect that it needs an replacement of LDU and rear half shaft. I had inspected the speed sensor and didn’t notice any sign of moisture. Are the rear half drive and LDU one unit or separate? I’m also inquiring thru the chat to ask which one is the cause of the original noise as well. Just wanted to share in case if others heard similar noise from rear drive area when moving from standstill position.
Half shafts are the axles that connect the unit to the wheels.

If you feel like you need a second opinion then it might be worthwhile to have an independent put in a new half shaft in and check for play.

If there's no coolant in the oil and the
splines are okay then the service center may be saying to replace the drive unit unnecessarily.

Did they give you a time estimate for getting a unit?
 
Half shafts are the axles that connect the unit to the wheels.

If you feel like you need a second opinion then it might be worthwhile to have an independent put in a new half shaft in and check for play.

If there's no coolant in the oil and the
splines are okay then the service center may be saying to replace the drive unit unnecessarily.

Did they give you a time estimate for getting a unit?
Thanks, I’m waiting to hear back from SC, on the estimate it indicates both half shafts being replaced. I also didn’t find anything on the estimate to indicate what the diagnostic indicated to be the cause of the original noise. It’s as though it seems like let’s just replace everything and the noise issue will be resolved, just figured they would have stated the why the items needed to be replaced. If the root cause is the half shaft(s), and not the LDU then replacing the LDU isn’t warranted unless they found something wrong with the LDU itself too. Just wished the estimate had more clarity.
 
If you do go for a second opinion then also confirm it's the original unit by getting a pic of the label on it.

There's a thread for finding and interpreting it.
Unfortunately in Northern California where I am there really isn’t another choice (no electrified garages nearby) besides Tesla SC’s to get a second opinion. I figured if SC comes back as the original noise being caused by loose half shaft (Not sure if both half shafts would cause the noise) but if both half shafts are in need of replacing that’s still better off than replacing the LDU if I can get away with it for couple of years as the car drove fine without any additional noise other than the click sound when leaving a standstill. But if the LDU is found to be the root cause of the noise, then I might as well get the half shafts replaced since it’s at the SC and I really don’t have any other choice in Northern California.
 

NewbyMaybe

Newby1Kenowby
May 3, 2021
543
176
Florida
An ordinary shop can jack up one side of the car and put it in tow mode to release the parking brake then try moving the raised wheel back and forth.

I'll be corrected if wrong but the down wheel might keep the drive unit stationary, if there's play then the half shaft is bad. Do this to both sides.

But new half shafts may only be a temporary fix if the spline in the drive unit is worn.
 
An ordinary shop can jack up one side of the car and put it in tow mode to release the parking brake then try moving the raised wheel back and forth.

I'll be corrected if wrong but the down wheel might keep the drive unit stationary, if there's play then the half shaft is bad. Do this to both sides.

But new half shafts may only be a temporary fix if the spline in the drive unit is worn.
Thanks again, hopefully SC will get back to me on the chat, regarding the diagnostics finding to justify the replacement of all 3 items. Since I did the speed sensor inspection, I have the low profile jack and puck, I could have checked the half shaft for any play prior to taking it to the service center if it allowed that with the other side not lifted. Good to know for the future though, thanks.
 
Hopefully the check is that simple, how long ago did the noise start?
I had purchased the car late last month, it had the click noise at that time. Not sure how long it had been going on though. I took the LDU, HV battery and MCU2 upgrade into consideration towards the purchase price and it still made sense to purchase it with the price I was paying even with if all three needed to be replaced. It’s getting the MCU2 upgrade while at the SC right now, that was one of the item I had with the clicking issue when I had setup the appointment.
 

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