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Model S Technical / Mechanical Issues

sonofagunn

Member
May 4, 2020
54
48
Florida
Just had my rear drive unit replaced after getting the error messages about reduced acceleration, regen, and car may not start. It is a 2014 P85+ with ~ 67000 miles. Got part number 1025598-00-T.
After living with the new DU for a while I am certain my efficiency is way better. My trip predictions are pretty much spot on even if I go 80+ on the interstate. Before the DU replacement, the trip predictions were *very* optimistic and I had to plan on stopping to charge before the trip computer said I would need to even if I were driving slower. I guess the old failing one had lost some efficiency.
 
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ajbessinger

EV Repair Technician at QC Charge
Sep 2, 2020
58
166
San Marcos California, USA
@ajbessinger are all Large Drive Units (LDU) susceptible to this type of failure, or just certain years/models?
Most LDUs are susceptible, apart from maybe some of the newer replacement ones (e.g., within the last 2 years or so), though I can't even say for sure if those are good for certain as I haven't opened one up yet. I would check the speed sensor for leakage at least once per year regardless of mileage or age, but especially if it has higher miles or is an original, older DU.
 

ajbessinger

EV Repair Technician at QC Charge
Sep 2, 2020
58
166
San Marcos California, USA
After living with the new DU for a while I am certain my efficiency is way better. My trip predictions are pretty much spot on even if I go 80+ on the interstate. Before the DU replacement, the trip predictions were *very* optimistic and I had to plan on stopping to charge before the trip computer said I would need to even if I were driving slower. I guess the old failing one had lost some efficiency.
Could be that the old one had started to build up corrosion on the rotor and commutator bars due to exposure to coolant. This will cause the rotor and commutator bars to start to contact each other and "rub", which would of course create a lot of added drag on the motor. At our shop we have frequently seen them get bad enough that the rotor seizes solid in the motor and will barely turn, even with full throttle (or may not even be able to turn at all). When they get to that point, the rotor has to be pressed out using a 20 ton shop press.

The car has no way of knowing that this has happened, so it won't send any sort of error messages until it gets to the point of a catastrophic failure. The error messages you got were likely related to coolant eventually making it's way to the inverter, which of course is game over as coolant + sensitive/HV electronics = bad stuff happening.

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2101Guy

Active Member
Jan 6, 2020
2,140
2,912
USA
The knowledge that AJBESSINGER has shared has really helped my understand these motors more, and most importantly, convinced me to excercise extreme caution if I were to consider going from my Long Range to used Performance S. Because its my understanding that even if you inspect and detect the leak on the rear drive unit? Its still several thousand dollars in cost to fix it. More if you dont catch it early.
 

Lewis88

Member
May 18, 2020
26
12
The Netherlands
So, what would happen if I remove my speed sensor and discover coolant, go to tesla and tell them it's failed? Possibly they deny anything is wrong and I should not touch such components/possibly voided warranty. Should I then rather cover the drive unit in coolant and tell them it's leaking and I read on the Internet the internal seal failed? I mean, warranty is warranty.
 

2101Guy

Active Member
Jan 6, 2020
2,140
2,912
USA
So, what would happen if I remove my speed sensor and discover coolant, go to tesla and tell them it's failed? Possibly they deny anything is wrong and I should not touch such components/possibly voided warranty. Should I then rather cover the drive unit in coolant and tell them it's leaking and I read on the Internet the internal seal failed? I mean, warranty is warranty.
I assume you are still under warranty? If so and if it were me, I'd most likely take photos of the leak and save the pics. I'd then not necessarily tell Tesla about the pics/removing the sensor unless they asked. But Id open a ticket with Tesla asking them to examine the drive unit at my cost if needed, as I heard that inspection of the rear drive unit is recommended by some. Im sure tesla would have no issue accepting your hours labor worth of cash for them to do a quick 5 minute inspection. I'd hope at that point they would A)Spot the leak B)Address the issue properly under the warranty coverage
 

KES16

Member
Sep 2, 2015
20
10
Toronto
Hey guys,

2014 Model S P85 with air suspension a few days ago as I was driving the Yellow air ride light came on and the rear driver side wheel was completely in fender (Not aired up)
I drove the car back home and aired it up to High and it did not leak all all. Went for a 5 min drive and did the exact same thing.

Because the car will stay at height when not being driven I am assuming there isnt a leak in the air system ( I had the rear struts replaced 60k ago and at that time they would sag after sitting so I knew there was a leak)

I am thinking it may be the Ride height sensor on the rear driver going bad.

Any thoughts?
 
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2101Guy

Active Member
Jan 6, 2020
2,140
2,912
USA
Hey guys,

2014 Model S P85 with air suspension a few days ago as I was driving the Yellow air ride light came on and the rear driver side wheel was completely in fender (Not aired up)
I drove the car back home and aired it up to High and it did not leak all all. Went for a 5 min drive and did the exact same thing.

Because the car will stay at height when not being driven I am assuming there isnt a leak in the air system ( I had the rear struts replaced 60k ago and at that time they would sag after sitting so I knew there was a leak)

I am thinking it may be the Ride height sensor on the rear driver going bad.

Any thoughts?
only way to know is to spray soapy water around the air hose connections at the various places to check for bubbles. Thats a good starting point for self-diagnosis
 

Gtech

Member
Dec 4, 2016
539
658
Netherlands, Berkel en Rodenrijs
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Relld05

Member
Mar 19, 2021
5
2
Texas
Hey TMC, maybe you all can help me, since the North Houston Service Center has failed to.
So, extremely similar to hpartsch, my 2017 CPO Model S is making that same creak/squeak sound. It apparently does this when the brakes are applied, either manually, or with AutoHold. Mine also makes a very clear grinding noise when turning the wheel close to it's max. I also get squaking when stopping, either forward or backward. Not the brakes, but when the car itself comes to a complete stops.

I just took delivery CPO direct from Tesla at 39k miles a couple months ago, so I'm still well under warranty... original and extended...

However, after taking it to the Service Center twice with that squeal as a noted issue, they've written it off as "rusty brakes". Speaking in person, I was told that the humidity was causing more rust than normal.... even though my brakes look to be perfectly shiny. It was not until recently, from built up frustration, that I found online that this looks to be a ball joint or suspension issue. I took this to the Service Center, provided the exact video below, and they came back and told me that was "normal". They say that the brakes rub when you turn the wheel, creating this extremely loud squeal and grind. When I asked why my luxury Tesla does this and not any other brand of car I was told "We can only state the facts" (literally all they said), and was asked if they could cancel my appointment.

So now I'm asking other Model S owners.... does the video below sound anything close to "normal" to you? This is the only Tesla I've owned, so maybe these cars just sound this terrible. It's embarrassing to even drive this thing in many situations.

Sidenote: Is there any way to "escalate" service issues?


 

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