DIY Tesla Drive Unit Repair

[howardc64]

I pulled my speed sensor for the first time. Guess it looks as expected. That flyover tube is going to be a real problem to remove.

Not sure you have coolant yet from those pics. EVERY SINGLE first speed sensor pull on LDU from Tesla looks like this (also confirmed with @ajbessinger at QCC) I believe Tesla is greasing the seal on install. All PTFE seal literature says to keep it clean on install but I'm guessing grease will just burn off the lip contact surface quickly. Tesla maybe greasing it for installation. Triple lip seal with excluder lip require experience and procedure to install properly without folding. Even single lip seal probably require quite a bit of force over the chamfer on the rotor shaft opening as PTFE seal lip (feels like hard plastic) is more than 2mm smaller than shaft diameter. Cutting PTFE seal lip will cause instant leak.

I think the spun off grease is what you see on yours so perhaps still very early stage to no leak yet stage.

Have also heard/seen some early S's able to get 100k+ miles and 8+ years without a leak. My guess is the grease on triple lip seal with its 2 in betwen lip chambers might have something to do with it. But no proof or careful study of course.

BTW, what is really strange is ALL seal of any type and any design leak some minute amount (eal designers work towards such specs. Doesn't make sense LDU seals don't leak even a little even if working as designed and we are talking about much thinner viscosity than oil. But its a sealed environment so not really sure where the leak went. Perhaps we are just not seeing an LDU opened up without chasing a leak to see its internal condition "before" noticeable leak.

 

[j.harris]

No turning back now. Managed to get it cut and plugged off.

 

[MrMoparMan]

No turning back now. Managed to get it cut and plugged off.

Looks great, nice job!

 

[j.harris]

The manifold has now been violated. I wish the m18 fuel oscillating tool wasn't so long. If I were to do it again I'd get the m12 version. Moparman's kit should be here tomorrow, I'm excited to get it back together.

 

[MrMoparMan]

The manifold has now been violated. I wish the m18 fuel oscillating tool wasn't so long. If I were to do it again I'd get the m12 version. mroparman's kit should be here tomorrow, I'm excited to get it back together.

You're not messing around! Nice cut, you'll have it back together in no time!

 

[j.harris]

Back together! Everything went well but access is so cramped none of it is fun. I would also like to note the bolts holding the new flange on are a little too long. The flange on mrmoparmans kit is thinner than the original manifold so it felt like the bolts were bottoming out before they tighten the flange completely. I added washers behind the heads of the bolts to take up the space.

 

[MrMoparMan]

Back together! Everything went well but access is so cramped none of it is fun. I would also like to note the bolts holding the new flange on are a little too long. The flange on mrmoparmans kit is thinner than the original manifold so it felt like the bolts were bottoming out before they tighten the flange completely. I added washers behind the heads of the bolts to take up the space.

Nice clean work! Good info on the bolts/washers, thanks.

 

[howardc64]

Regarding running the PTFE seal dry, the other concern would be frictional heat. When installing a new PTFE seal, its sized like 2mm+ less than the 30mm shaft and material is like hard plastic. At least initially, it grabs pretty tight and would provide some friction.

A triple lip PTFE seal surely has its excluder lip (closest to the bearing) running dry but the shaft is getting cooled by coolant. With shaft cooling removed, dry running lip's frictional heat has no place to go.

Don't really know how much problem this is in addition to the rotor not getting cooled. Just noting for reference.

 

[asavage]

I would also like to note the bolts holding the new flange on are a little too long.

On mine, all six M6 holes had excess RTV in the bottoms. I re-ran all the holes with an M6 tap, so I could use the entire holes' depth.

I needed full-depth holes on the upper four for the puller bolts to remove the end cap without beating or prying on things.

[This forum's software is configured such that it won't accept the filesize of the pic of the puller, and I refuse to make it smaller to accommodate it on one forum, so the puller is shown over there.]

 

[Hank42]

Good thread with lots of information and options! Took the easy way out and eliminated cooling to the rotor and diff by cutting off the original cooling manifold and just gave full flow to the stator. I removed the coolant tube and capped off either end. Been running it for a few weeks and everything seems great, possibly slightly lower stator temperatures.

What is this part? Custom made? 3d printable?

 

[MrMoparMan]

What is this part? Custom made? 3d printable?
View attachment 1047501

I make them, The aluminum is most popular but I also print polycarbonate.

 

[j.harris]

On mine, all six M6 holes had excess RTV in the bottoms. I re-ran all the holes with an M6 tap, so I could use the entire holes' depth.

You are correct my bolts had silicone at the ends. I didn't think to try to clean it out with a tap but I also don't have a m6 bottoming tap.

 

[mr_hyde]

Sounds great.
Please keep us posted when you get some caps.
I could setup a webshop but as you said better to go with an existing platform.
If you change your mind I would be happy to buy one from you
Regards
// Per

The production run of caps will be available around the end of the month. I'll put single units on ebay for DIYers and wholesale larger quantities to shops that are interested. There are four prototypes out in the world including the one in Howard's car and it is working great!

 

[howardc64]

Hello everyone,

I find myself in a similar situation where I received a message on my display (2014 MS P85, got the “P” version LDU in 2017) regarding a potential coolant leakage issue that may prevent my car from starting. Before I embark on the repair process (rotor coolant delete), I'm ensuring I have all the necessary parts. According to the service manual and common practice, it's essential to replace certain o-rings and seals. Does anyone have a comprehensive list of sizes for these components? While I know Tesla provides these (not all, jsut most of the) parts, I'm uncertain about their prices and would prefer to explore local shops for alternatives. (2 pcs Axle seal, HV cables,Pipes,Coolant line o-rings, etc)
Around the bearings there is a special red o-ring size is unknown?! What is the purpose using o ring on the bearing house? (I saw that cad youtube video from DIY EV Guy)

In my town there is a Toyota official service but Tesla is far away.

I've managed to locate the sizes for the bearings online (btw this community is amazing!). As I'm based in the EU, I'm opting for SKF hybrid bearings. Oil will be Dexron VI, 1.4 litres.
Silicone will be CX-80 or Permatex Ultra Black.

Additionally, for those in Portugal, I stumbled upon a coolant delete kit available at:

Tesla LDU SEAL DELETE kits | speev
Thank you in advance for any assistance provided.

Axel seal is $4 each at Tesla ~2 years ago. Seal comes pre greased

No reason to change o-rings for B+ B- cover, 3 phase bolt cover, coolant inlet, speed sensor. Flyover tube. Nothing happens to these. Can reuse.

The rotor bearing oring is just there to stop outer race from spinning in the bore. No need to change. Johan’s inner bore had no oring (seems to be the case on RAV4 EV LDUs) so needed to be glued down. My rev Q LDU had oring on both bores and no Locktite was necessary.

Most desirable o-rings to replace are unique shape and Tesla do not sell. Manifold to motor end plate. End plate to stator housing. Between the gearbox halves. These get RTV on them and I couldn’t even get all the permatex black RTV off of them on the 3rd rebuild. Since not sold, have to preserve them

3 orings if pull the inverter can be reused but need to not crimp/rip them on reinstall. My earlier post on this thread shows alignment method. It’s advisable to not pull inverter if possible. Mounting bolts are too short and bite on only 1 thread into the alum gearbox mount holes. My reman LDU had 2 stripped from Tesla. Longer bolts (18mm instead of 16) is possible. Need small head to clear nearby walls (hardware store hex heads were narrow, VW torx heads too big, will bite into the wall and strip threads) all this noted on my prior posts in this thread.

In summary, get axle seal. No need to buy orings but careful cleaning thise that may have some RTV on them.

If inner rotor bearing is glued or rusted onto the bore, may need more specialized tooling to get it out.

 

[Hank42]

Incredibly stupid question - in the middle of a rebuild due to HVIL fault on a Rev Q Unit installed by Tesla. Thought I found my culprit - as I had low impedance between ground and B+ on the input lead (~400Kohm vs > 2Mohm). Replaced the B+/B- harness and impedance checks out. No sign of coolant in the inverter cavity at all. Some signs of coolant on the speed sensor - so I installed the QC charge bypass on it.
Before reassembly, for giggles, I measured the Impedance on the windings to ground and I see a dead short on all three phases.

Just for sanity check ,that is not NORMAL right?
(I mean, I know it is wrong, but that glass half full part of me is really wishing someone will tell me I know nothing about electronics and that that is normal LOL)

I guess I'll pull the inverter apart to see if its a dead short on the inverter side or the motor side. Was really hoping to not have to do that.

 

[asavage]

Before you waste too much time and money on parts, be sure to disassemble the unit and check the resistance of each winding of the stator. If it has an internal short you need a completely new drive unit. I have three with dead shorts in the stator windings.

A ReVolt representative has said:

I can't get into the specifics, but we found a solution that dissolves the crystallized coolant without affecting the stator potting material nor the wiring insulation. Our method takes a stator with iso under 200k ohm and gets it to 40M ohm or higher (typical lately is 80 to 120 megaohm). We also replace the ceramic bearings, coolant seal, and perform the weep hole we have posted elsewhere about.

It seems that some of the wet stators may be revived.

 

[asavage]

. . . in the middle of a rebuild due to HVIL fault on a Rev Q Unit installed by Tesla. Thought I found my culprit - as I had low impedance between ground and B+ on the input lead (~400Kohm vs > 2Mohm).

The High Voltage Interlock Loop (HVIL) is designed to make certain that all HV wire harness connectors are properly installed, prior to the HV contactors closing. It does not measure HV isolation.

The HVIL has many 60 ohm resistors in series; if the loop resistance doesn't add up to the correct resistance (60 * n = total; the number if resistors has varied over the years on the Model S), then an HVIL error occurs. I don't see how this ties in with low insulation isolation resistance.

From the SB-10052449-4313 HVIL Diagnostic Guide:

I guess if your LDU's data connector got wet enough (on the inside, inverter side), it could foul that loop, but you'd see that pretty easily with the inverter cover off, or by using a standard ohmmeter (DMM) on the LDU data connector terminals 7 & 8 to ground (should be open/∞).

Replaced the B+/B- harness and impedance checks out. No sign of coolant in the inverter cavity at all. Some signs of coolant on the speed sensor - so I installed the QC charge bypass on it.
Before reassembly, for giggles, I measured the Impedance on the windings to ground and I see a dead short on all three phases.

Just for sanity check, that is not NORMAL right?

Correct. On my recent LDU repair, measuring from the three bolts (under the center orange plastic cover) of the stator windings to inverter, to ground, I saw ~4.7Mohm (using a Fluke 1507 Insulation Tester, which applies 500v to the circuit and measures decay).

HV Isolation Testing SB-10052460-6095

 

[Hank42]

The High Voltage Interlock Loop (HVIL) is designed to make certain that all HV wire harness connectors are properly installed, prior to the HV contactors closing. It does not measure HV isolation.

The HVIL has many 60 ohm resistors in series; if the loop resistance doesn't add up to the correct resistance (60 * n = total; the number if resistors has varied over the years on the Model S), then an HVIL error occurs. I don't see how this ties in with low insulation isolation resistance.

From the SB-10052449-4313 HVIL Diagnostic Guide:

View attachment 1048180

View attachment 1048179

I guess if your LDU's data connector got wet enough (on the inside, inverter side), it could foul that loop, but you'd see that pretty easily with the inverter cover off, or by using a standard ohmmeter (DMM) on the LDU data connector terminals 7 & 8 to ground (should be open/∞).



Correct. On my recent LDU repair, measuring from the three bolts (under the center orange plastic cover) of the stator windings to inverter, to ground, I saw ~4.7Mohm (using a Fluke 1507 Insulation Tester, which applies 500v to the circuit and measures decay).

HV Isolation Testing SB-10052460-6095

Sadly, I'm all too familiar with the HVIL loop diagrams But I do thank you for the hope on the stator windings - If it were crystalized coolant, I'd expect to see some resistance, I'm registering a dead short (less than 2 ohms yikes!). [using AMPROBE AMB-25 Mega-ohmeter set to 500V] But won't know until I separate the windings from mosfets - -maybe I'll attack that tomorrow - just such a PITA to pull the motor assembly apart - need to set up a better work bench to handle the blood that's sure to spill when I crack the case (gearbox fluid ) And thanks for the confirmation and readings I should expect to find on the stator windings if/when I fix it.

 

[asavage]

You don't have to split the gearcase to pull the inverter stack, or the rotor. It's only when you really need to get to gearbox bearings, or you have a rotor that has to be pressed out from the pinion gear side, that you have to open the gearcase.

Exception: if you're going to have your stator soaked in magic dissolver or rewound or something like that. Yeah, it's got to be completely disassembled for those.

I was able to bend a 90° on the end of some thin plastic strips I cut from deli trays or something, and carefully slip them behind the stator wires when the bolts were removed, isolating the stator from the inverter's IGBTs. But I didn't need to, I just wanted an A-B comparison of the iso test results, which were minimal. You might try that before pulling the inverter stack, as Howard notes the problems with the fixing bolts he had (too short, not enough thread engagement, threads pulled after reman; o-ring seating difficult to verify/easy to damage). If you can test the IGBT outputs while isolated from the stator and without pulling the inverter stack . . . might glean valuable info to inform your next move, without diving off the deep end immediately.

 

[Hank42]

You don't have to split the gearcase to pull the inverter stack, or the rotor. It's only when you really need to get to gearbox bearings, or you have a rotor that has to be pressed out from the pinion gear side, that you have to open the gearcase.

Exception: if you're going to have your stator soaked in magic dissolver or rewound or something like that. Yeah, it's got to be completely disassembled for those.

I was able to bend a 90° on the end of some thin plastic strips I cut from deli trays or something, and carefully slip them behind the stator wires when the bolts were removed, isolating the stator from the inverter's IGBTs. But I didn't need to, I just wanted an A-B comparison of the iso test results, which were minimal. You might try that before pulling the inverter stack, as Howard notes the problems with the fixing bolts he had (too short, not enough thread engagement, threads pulled after reman; o-ring seating difficult to verify/easy to damage). If you can test the IGBT outputs while isolated from the stator and without pulling the inverter stack . . . might glean valuable info to inform your next move, without diving off the deep end immediately.

Thanks for the tip - I'll give that a go since what you did is exactly what I am tying to accomplish - test the stator resistance while disconnected from the inverter.