I want to thank ajbessinger for his information on rear drive unit failure (sorry can't find the thread) and how to check the speed sensor for coolant leakage. My 2/15 p85D with original drive unit was showing no failure symptoms, but I asked the service center to check the speed sensor for leakage and was rewarded a new drive unit for it. The replacement drive unit is up to revision 'T' BTW. So if you're still under warranty, ask them to inspect it. Might save you a small fortune.
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Have your service center check large rear drive unit for coolant leakage before warranty expires
- Thread starter Asummers
- Start date
The coolant may not be dripping/visible externally. Have to actually remove the speed sensor to look inside. If the speed sensor has any trace of coolant on it? The internal seal on the DU has failed. And total drive unit failure is pending unless addressed fairly quickly
This is the best advice for all teslas model s with large rear drive unit!
My 2012 Model S Signature 85 (out of warranty) had a diagnosis of a bad HV battery from Tesla service center. They were wrong as I did change the hv battery and still had the errors. The DU was the original issue, and the inverter was completely shot so could not have it re-built by a 3rd party. Ultimately went to a different Tesla service center to replace with a rebuilt DU (4-year/50,000 mile warranty).
Original DU lasted 53k miles (buzzing/sawing noise) and covered under warranty. 2nd DU lasted 60k miles (coolant leak failed seal and failed inverter) out of warranty. 3rd new DU on car now 115k miles, and will check speed sensor maybe at 15k-20k on the DU to check for coolant leaks to prevent catastrophe!
My 2012 Model S Signature 85 (out of warranty) had a diagnosis of a bad HV battery from Tesla service center. They were wrong as I did change the hv battery and still had the errors. The DU was the original issue, and the inverter was completely shot so could not have it re-built by a 3rd party. Ultimately went to a different Tesla service center to replace with a rebuilt DU (4-year/50,000 mile warranty).
Original DU lasted 53k miles (buzzing/sawing noise) and covered under warranty. 2nd DU lasted 60k miles (coolant leak failed seal and failed inverter) out of warranty. 3rd new DU on car now 115k miles, and will check speed sensor maybe at 15k-20k on the DU to check for coolant leaks to prevent catastrophe!
I pulled my car's frunk recall paper and annotated what OP said, will have them check as this will be the last service before 8 yrs are over and will not get a replacement until after WW3 is over and the economy picks up minus half the mankind.
Jpandes
Member
Can I check this thing myself? Or will Tesla notice that “someone” other than Tesla tampered with it and try to deny the warranty claim?
Yes you can. They can always TRY to deny, but wouldnt hold up under federal law (Magnusson act) which puts burden of proof on the mfr to show that a modification done to the car is the issue for a part/system failing. Simple removal and inspection followed by proper replacement of a sensor, doesnt constitute a modification
airborne spoon
Active Member
i like the way you think on getting around stuff to get them to inspect thoroughly. Do i just make an appt saying inspect my speed sensor? or do i need to say something is wrong? like should i say my speedometer is reading differently than the radar signs on the highway?
NewbyMaybe
Newby1Kenowby
I learned today that you agree to the diagnostics fee. If there's nothing wrong then you win. If there's a problem covered by warranty then you win.
I have a 2013 model s p85 w/ 62k miles, the DU was replaced under warranty in 2020 with less than 50k miles. New battery in 2022 with 60k miles ($14k). Does anyone know if Tesla has actually fixed the large (sport/performance model) drive units on the replacements? I know Rich Rebuilds ended up putting an s60 drive unit in his 2012 model s p85 and he hasn't replaced it since. I was curious if anyone knows why the coolant is failing - is it heat buildup, lack of coolant flush/changes, fluid interval of 50k miles too much? Since I am now out of warranty on the car (battery still has time) I wanted to know what I can do to get 100k out of this DU. Changing fluids every 10-20k would work for me if it solves the problem. Thanks - Brock
NewbyMaybe
Newby1Kenowby
The o-ring seals fail, allowing coolant to get into the gear oil and electric components.
The 4 year warranty on your drive unit will probably save you.
Not much can be done until they get the o-rings improved or redesigned.
As I understand it, there is no longer a warranty on the DU since it was replaced under warranty in 2020. The car is now 9 years old. The battery was done in 2022 and should have the 4 year warranty. So basically what you are saying is that the o-rings could possibly be replaced pro-actively every 30k miles or so before a failure and re-lube the hybrid bearings at the same time. There is a youtube channel called DIY Tesla Drive Unit repair and it's quite thorough thus far in terms of DIY the whole process. I wonder if it's possible to swell the gasket with something and change the fluid as these reach 30-40k miles to extend the life of the o-ring. It would be interesting to find a used drive unit cheap and run a bunch of tests to see if it can be fixed on the test bench.
ucmndd
Well-Known Member
No, not really. The non-performance AWD cars have fewer problems because they use the “small” drive unit both front and rear, which doesn’t have the same design issue.
All cars that use the large rear drive unit, be they RWD-only cars or AWD performance models, have the same fundamental issue.
ucmndd
Well-Known Member
This is correct. Warranty replacements have no additional warranty beyond what was originally provided with the car.
ajbessinger
Owner of QC Charge #2 (Portland OR)
It's not really that the workload is shared, it's that the Small Drive Units are a COMPLETELY different design than the Large Drive Units. In a Dual Motor Model S/X, the front actually does most of the work except when accelerating hard. The failure mode actually has nothing to do with workload. I don't think there is any correlation between how much power, or how hard the car is driven in terms of how often they fail.
The biggest difference that the Dual Motor (NON-Performance) car have going for them is that the SDUs are oil cooled, and have no seals in the motor to go bad. The rotor, windings, and bearings all have oil squirters or drip systems that lubricate and cool everything off, and since the oil is non-conductive, there's no need for any seals or separation from the windings or conductors. The LDUs that were used in RWD or Performance versions of the S/X on the other hand are "water" cooled, and have a seal to keep the conductive, water based coolant out of the windings and conductors. The problem is that the seal wears out, and then allows coolant to leak into places where it shouldn't be, which causes a buildup of rust in the motor, creates HV isolation issues, and can destroy the circuit boards on the inverter.
Also, the seal that fails is NOT an O-ring seal, its a PTFE lip seal, which is supposed to hold up to the high surface speeds that the rotor spins at (at highway speed, the surface speeds are ~2,000-2,500 SF/M, and at "redline", approach 5,000 SF/M). Around 2015, Tesla switched from a triple lip PTFE seal to a single lip design, which seems way more prone to premature failure. Most of those earlier style motors were replaced due to bearing noise issues since they had steel bearings on the rotor, but that's a different discussion... The point is that the newer style motors are MORE prone to coolant leakage than the early ones. Why they have continued to use that single lip seal design that seems so flawed, I have no idea, but I've even taken apart some of the very newest revision motors (including those with the newer style differential that has 6 spider gears instead of 4), and they are still using the same crappy seal that they have been for years now.
There's really no "permanent" fix for the issue, as it really just comes down to the fact that the rotor cooling setup on the LDU is just a flawed design because the of the seal. Unfortunately the nature of seals is that they will always wear out eventually one way or another... I think that driving the car regularly helps though, I've noticed a trend that cars with really low miles tend to have more seal issues than cars that get driven more often. The only other things you can really do are be proactive about regularly checking the speed sensor for signs of coolant (once a year MINIMUM), and get it taken care of as soon as you see a problem. If you wait until the car starts to get isolation faults, or stops running entirely, it gets a lot more expensive to repair... When we rebuild the Drive Units at our shop, we add a drain kit to mitigate future coolant intrusion, seal up the passages between the motor and inverter, and of course and we also utilize a triple lip seal much like the original that Tesla used (not to mention of course the ceramic bearings and all as well).
ajbessinger
Owner of QC Charge #2 (Portland OR)
Not sure, but maybe the seals hardening up due to a lack of cycling/movement? It's mainly just an observation I've made, not sure how accurate it is, but I work on a lot of these motors...
Most of the seals I've seen go bad at low mileage were in cars that were not driven very often (e.g., under 5k mi per year). I've even seen seals go bad within a year or two of a new motor being installed in a car, and in most of those cases, they had had less than 10k mi put on them (some even as little as 2-3k mi). On the cars that are driven regularly though, the seals seem to last longer in my experience.
There are similarities to that with seals on ICE engines too, a lot of the time cars that sit for extended periods of time develop major leaks because the rubber seals harden up, which leads to diminished sealing properties, and makes them get worn out quicker. Rubber definitely hardens over time if not cycled often (look at tires as an example). The PTFE seals in the LDU are a totally different material from rubber, but it seems like they have similar properties in that respect. Either that, or maybe the seals never got a chance to be properly broken it to mate with the sealing surface and form a tight seal.
