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Drive unit coolant leak, tear down/test/repair (hopefully)

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Hello all,

This is my first post. I have a 2013 Model S, salvage, recertified car. Owned it for a little over a year and wanted to get this information out there as I had a lot of difficulty finding anything. This means the car has no warranties. I finally got a straight answer from Tesla on this, battery and DU warranty are not valid. I was told a handful of times that I did still have battery and drive unit warranty, but after a little persistence finally got an "official" email and document from Tesla confirming it is not active.

Going back to the beginning of March, I got an error message. "Car needs service. May not restart". After my drive home (lucky I was on the way home when I got the error) and I parked the car, I tried searching online for potential troubleshooting. I went back out to the car, got in and saw "Systems shutting down". Everything went black. My local service center was in the middle of a move to a new location and I wasn't able to get in touch with them. I spoke to the phone technical help multiple times and tried to get information related to what my error codes were actually related to on the car. My first conversation lead me to believe I had a HV issue based on the technical support interpretation of the code. Also, the car going black was because the HV issue wasn't charging the 12V battery. Photo tech support told me about the charging posts behind the nose cone, so I hooked up a battery charger and let the car sit. Later that day I went out to the car and it was again powering up, and had no immediate error codes.

The next few days I spent discussion the warranty question, finally got a hold of the service center, discussed whether Tesla would tow the car for service (told they would not send a truck as it was out of warranty and I would need to call a towing service to get the car there, later was asked if they wanted me to have them send a tow truck and charge it to the repair service) and ultimately decided I would take the car in for service. At this point I was still under the assumption, based on my calls with phone tech support, that I did still have a batter/DU warranty. The last call I had, I was told, get the car there as soon as possible.

So, one day after work, I decided if the car would "start", I would try and drive it to the service center (the location they were moving from per the address phone tech support told me to go to). I arrived and was lucky to find a sales person still there, as all the service department had already moved to the new location. Finally someone showed up that was able to help with service and apologized about the confusion, explained the move, and said leave the car, then gave me a loaner. I was a little surprised by the loaner.

The next week, I got a call. There was a HV isolation issue. Water/moisture was in my drive unit and I was sent a picture of the orange cover on the inverter side of the DU with condensation on it. I was told I needed a new DU, $7,000 with taxes for parts and labor. I started to research the drive unit, learned there was coolant running though the unit and then asked the SC, water or coolant??? I was told water. I began going through the process of asking to buy the DU outright (obviously no), then can I buy a used DU and have Tesla push firmware (again no) and ultimately left with either Tesla does the work or the car will never drive again.

I kept driving the loaner, trying to exhaust all my options, ultimately getting a hold of someone on here. The people I needed to learn from for how to do the swap myself and get firmware pushed. At this point, Tesla was getting fairly angry that I was just drying their loaner without having given them the approval to fix the car, so I had to return the car. I probably had it 2, maybe 3 weeks. Throughout that time, I continued to try and connect to the car through the app and had limited success. So before I dropped the loaner off, I asked them to charge the 12v on the car, which the actually did. And even though they had told me the contactors wouldn't close in order to be able to charge the HV battery, the day I was set to pick it up, they started charging the car (thanks to the app notification I found out). Side note - I was also told the car wouldn't drive and charging the 12v would only allow the car to power up and that if I did drive it would be on 12v power alone HAHA.

Anyway, drove the car home, error message sporadically coming on the whole way but nothing noticeable on the drive. Car sat for a few days. Randomly checked app connection and even tried to drive a few times. No issues really except for the error code, and it was very random. Would come on then go off, come back on....

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I finally decided, due to the help from the members here and the posts, I'm going to take out this DU. Basically this is were it gets good, but I thought the long back story would be good for all those people that might run into similar issues and question. Got the drive unit out, pulled the inverter cover off and immediately saw a droplet of moisture. Got the cover fully off and sure enough, there was liquid. But it wasn't water, it's coolant. This leads to the question. Can you please off coolant from an inverter and what areas would/could be affected by the coolant. Thanks to some more off from a member on here, I learned that DU's can be saved and how to start cleaning the inverter. Also a potential way of testing the inverter to see if it's "fixed" before it goes back in, using a megohmmeter. That's where we stand right now, testing of the inverter and how to test the inverter.

There's plenty more to this story and pictures coming soon. This was all done on the garage floor without any fancy tools (except the megohmmeter which I just bought). Hoping this all works out, not just because I'll be able to drive the car again, but so other's know it's possible. Oh....and figuring out how to fix that coolant leak!!

Shane
 
To date, it seems that Tesla's answer to drive unit issues is simply replace it. This is not a realistic answer for someone without the DU warranty. This has not been an issue for me so far, but my DU warranty is up in a little more than 2 years - and I just had another replacement due to an unfamiliar noise.
These are not magic boxes, and something as mundane as a coolant leak should not cost $7k to remedy.

Thanks for this thread, and looking forward to progress updates!
 
I believe someone on here posted the instructions to redepoly firmware if you decide to go the used drive unit route. It was a pretty simple process of hooking a laptop in behind the AP computer and sending a command over telnet.
 
I admire those who are willing to pioneer the DIY/independent mechanic route of Tesla. To date it seems like Tesla does sporadic updates/revisements and swaps out the troubled part for one in their inventory. We all assume Tesla is remanufacturing/refurbishing the questionable unit (battery modules, drive unit, axles, etc). What we haven't seen is an aftermarket supplier support or parts servicer which makes most of us dependent on Tesla Service Centers.

I can understand why the service center would be annoyed by your case. They weren't getting any money from you, you took an extended loaner from them, and you took up space on their facility for some time. However, I am very sympathetic that out of warranty owners face some pretty high repair costs for batteries and drive units. I would hope that you'd see a 50% off reman price (with perhaps 50% of the warranty of a new unit). Secondly, if they want $7K for a replacement DU, what would they be willing to buy your old DU for? Most would just surrender it, but how ridiculous would it be if that "troubled" DU just needed $50 of replacement parts and resealing?
 
Have you located the leak?
There are 3 o-rings that seal each channel of coolant to the inverter. I have not found any issues here and have looked at the aluminum housing that the coolant runs though. Long story short, no. I do intend to apply slight pressure to the inverter coolant housing to test those. Otherwise, I've measure the o-rings and will be measuring the grooves to see if I can put in a new o-ring.

I believe someone on here posted the instructions to redepoly firmware if you decide to go the used drive unit route. It was a pretty simple process of hooking a laptop in behind the AP computer and sending a command over telnet.
My understanding is this can only be done in certain states that have access to Tesla Toolbox, or someone that has learned how to hack the cars. I'm not in one of those states but have found the right guy that can help with the firmware push.

I admire those who are willing to pioneer the DIY/independent mechanic route of Tesla. To date it seems like Tesla does sporadic updates/revisements and swaps out the troubled part for one in their inventory. We all assume Tesla is remanufacturing/refurbishing the questionable unit (battery modules, drive unit, axles, etc). What we haven't seen is an aftermarket supplier support or parts servicer which makes most of us dependent on Tesla Service Centers.

I can understand why the service center would be annoyed by your case. They weren't getting any money from you, you took an extended loaner from them, and you took up space on their facility for some time. However, I am very sympathetic that out of warranty owners face some pretty high repair costs for batteries and drive units. I would hope that you'd see a 50% off reman price (with perhaps 50% of the warranty of a new unit). Secondly, if they want $7K for a replacement DU, what would they be willing to buy your old DU for? Most would just surrender it, but how ridiculous would it be if that "troubled" DU just needed $50 of replacement parts and resealing?
I asked multiple times, they had plenty of loaners and that wasn't an issue. I did have to pay for their diagnostic time, 1 hour. And, the DU would be kept by Tesla, no questions asked. How dare they leave me with such a "dangerous" component. New DU came with 1 year warranty only which also helped me to decide it wasn't really worth it to have them replace when it could happen a year later and they would want the money to replace again.
 
My understanding is this can only be done in certain states that have access to Tesla Toolbox, or someone that has learned how to hack the cars. I'm not in one of those states but have found the right guy that can help with the firmware push.

No toolbox required. It was connecting to ethernet and sending a command. I'll see if I can find the post.
 
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Basic removal pictures

First sign of coolant in inverter case

Obvious coolant in inverter case, although not that much
 

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Attempts to clean. Using IPA (91% rubbing alcohol). No major signs of coolant except for at the HV leads, boards all looked clean.

Last picture is my attempt to heat and suck out moisture. Makeshift greenhouse with a large container of DampRid to hopefully remove high humidity air. Placed this in front of a large window in my house for a few days.
 

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I wonder if you can bake that out in an oven set on low?
My initial thought is yes. I've also heard this has been done from Ingineerix. My concern is this isn't just water. It's coolant, so assuming it's propylene glycol and water. After trying to research to get the coolant off, i've basically seen water and dish soap. I'm sure there is a solution cleaner out there that would work but I haven't been able to find it for PCB's. Hoping this doesn't need to happen and my megohmmeter will prove that, but that's my next steps.

The testing and readings I got last night are not what I was expecting and basically say that the inverter is "bad". But I'm not testing like you would for a typical motor test, it's an inverter. More testing to occur tonight. After talking to the meter manufacturer, Fluke, they are as confused as me when it comes to how to properly test and the values I was getting. I also have a call into Megger, original test meter manufacturer, to get their perspective. But once I began explain my application I was told "You can use this on a car". I said "It's an electric car, it's a DC power supply to an inverter to a motor." I think they have no idea Tesla or electric cars exist.
 
I'm attempting to a do a megger test and I'm getting strange results. Now I'm not sure if I can even do this test on an inverter. I've tested the main two leads at 50V first, then 100V, then 250V, then 500V. Each time the meter will slowly ramp up to 15-16V and stop. The insulation resistance will show as .01 Mohm, the lowest possible display value. I took of the main two leads and tested each individual section of the inverter and nearly the same thing. I tested at 50V, tested at 100V. The meter this time was able to achieve the voltages, but at only .12 Mohm of insulation resistance. All three legs of the inverter tested exactly the same. I haven't looked and probably not able to tell if the inverter will ever allow this test to be performed correctly. Is it a closed loop that this type of test can perform? Definitely a little confused right now.

Testing images below.

I'm slightly encouraged that all the values are the same across the different inverter sides, but it worries me that I am getting values so far off what I expected. On the motor, I decided to test as well. Checking between the leads, I get nothing. Not voltage output from the meter and no resistance (assuming the voltage won't rise because there is no resistance). I did an earth-fault test, and everything tested fine (I think).
 

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Well, after inspecting the o-rings another time, I still see no issues with them and I'm a little hesitant to try and find a replacement of the exact same size. 1, because these look perfectly clean and no damage. 2, will getting exactly the same size really fix the issue if the originals are not damaged. 3, I can only measure the o-rings and the groove and I don't want to end up getting a slightly incorrect o-ring and making them all leak.

So, after looking at the sealing on the gear box, there are multiple o-rings that were also "passed over" with the gasket maker on the sealing surface between the casing halfs. So, basically, if Tesla is using RTV around the o-rings that supply coolant to the inverter, through the gear box casing, I should be able to do the same at the inverter sealing surface. My intent is to only place the RTV on the outside sealing surface of the mating pieces, and not actually get it in the o-ring groove, but with installation and the squeeze from tightening, I know some of the sealant will make it's way to the groove. Obviously I don't want to negatively effect the o-ring compression.

Picture of this installation are attached.

Now I'm hoping it's all sealed up and won't have this issue again. I need to get the transmission fluid to fill the gear box and I can reinstall.
 

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I asked multiple times, they had plenty of loaners and that wasn't an issue. I did have to pay for their diagnostic time, 1 hour. And, the DU would be kept by Tesla, no questions asked. How dare they leave me with such a "dangerous" component. New DU came with 1 year warranty only which also helped me to decide it wasn't really worth it to have them replace when it could happen a year later and they would want the money to replace again.

Apparently they don't know their own warranties:

The Tesla Parts, Body & Paint Repair Limited Warranty begins on the purchase date of the part(s), and coverage extends for a period of 12 months. Specific categories of parts have unique warranty coverage periods:
  • Sheet metal: Limited lifetime
  • Drive Unit: 4 years or 50,000 miles, whichever comes first
  • Vehicle High Voltage Battery: 4 years or 50,000 miles, whichever comes first
  • Wall Connectors: 4 years
  • Touchscreen and microcontroller unit: 4 years

But that isn't really surprising as they probably haven't sold any drive units out of warranty yet.