Tesla Coolant Delete: How This Simple Fix Can Save Your Tesla Model S/X Drive Unit

Join Amber’s Bobby Tessmar as he travels to Great Lakes EV to learn from owners Suzi and Pete about a coolant delete that can save the drive unit on 2012-2020 Tesla Models S and X. The Tesla large drive units on these models contain a coolant valve that routinely fails; the coolant delete prevents coolant leaks that can cause costly damage to the drive unit and potentially full failure if left unchecked.

Get a firsthand walkthrough of the issue from Suzi and Pete, the repair, and the steps you can take to protect your Tesla for long-term ownership.

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Video Transcript: 

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Bobby: Today, I am headed to meet up with Susie and Pete, who are the owners of Great Lakes EV in Dayton, Ohio—an independent repair shop that services mostly Teslas. They are going to be walking me through the process of an LDU coolant delete on a Tesla Model S.

We're going to be learning firsthand how the modification is done, why it matters, and what Tesla owners should know before considering this mod. I'll be arriving at the shop in just a few minutes, so we'll check back in when we get there with Susie and Pete.

Pete: What we're doing right now is related to a pattern failure in Teslas. The vehicles affected are 2012 through 2020 models—anything with the larger drive. To narrow it down, it's either rear-wheel drive or performance models. The larger Drive Unit has a coolant seal that will always fail. Tesla didn't catch it because, originally, the pattern failure with LDUs was bearings. So they basically replaced all these motors back in the beginning. They assumed it was all bearings, and then they made changes to the cooling system.

They said, "Oh, our coolant seal design is good," and they reduced the number of lips in the coolant seal. But then they leaked much faster in the second revision. So basically, right now, you have something coming to a head where all of the original motors are reaching the end of their life because the coolant seals are finally failing. At the same time, all of the newer motors with the less robust coolant seal are also failing. We are doing multiple of these a week.

They are fixable. Tesla's answer is, "Hey, let's throw an $8,000 new Drive Unit in it," but they're fixable, and you can even repair them preventatively. Actually, over here, I can show you one of these motors. This is the larger Drive Unit. This is the notorious coolant manifold. You'll hear a lot of people talking about how you need to pull your speed sensor to check for coolant ingress because that's basically where you'll first see it. Coolant enters the manifold here, flows through the stator, but also flows through the rotor, and then comes back through this flyover tube.

The process that we do is to delete that coolant channel through the rotor. Basically, unless you're exclusively using the vehicle for towing or driving on the Autobahn, you do not need this coolant channel. If you do want the high-performance option, there are ways to install an upgraded seal. This just gives you an idea of what one of these looks like out of the car. That’s the actual motor portion. This is the gearbox, which is just a gear reduction, and then you have the inverter side. This covers all the big, fancy power electronics. You can see some of those out of the car right there. Some of those are bad phases, so we have to go through and diagnose and repair them.

These systems are modular, and we can actually go in there and completely repair the stators, rotors, and the inverter electronics.

Okay, so now we free up the cables—oh, they came right out. Oh no, no way. These cables—so part of the reason that we make sure we leave the back doors unlatched is that, in lots of these cars, especially when there's a lot of coolant ingress, the cables will get stuck in the motor. There have been times where we've even had to suspend the motor in the air.

Alright, cables are clear. I'm going to start dropping down the lift table. Oh, this hose clamp was caught. There we go. Okay, come off the battery tab. Now we're back on track.

It's a "Q." Of course, it's a "Q." Alright. So then we’ll line up the stand. The heavy side is the stator. Oh, that’s why it's supported from that side too—because that's the big, heavy side.

They were so loud. Now we do the thing that most shops can do to pre-inspect these.

Alright, so yeah, not a horrible amount of coolant, but that right there is bearing grease. So we know that we have some—well, we can hear that. But actually, from the amount that's on there, it means that most of it's probably spread out, so there's probably not a lot of grease left for the bearings.

Here we go. Not terrible. Not terrible at all. Yep, so there's our coolant seal, and we can see there's all kinds of bearing grease in it.

These motors have all kinds of different writing on them—it's so inconsistent. It's pretty wild.

Here, I'll take these back up front.

Hey, the rotor's moving! That's a good day when the rotor moves.

Yeah, okay, so the bearings are destroyed on this unit, but this actually isn't terrible. Oh yeah, look at all the bearing grease in this case. That used to be bearing grease. It is no longer bearing grease.

Oh, it's dry. Yeah, interesting. Oh yeah, new. So this customer actually got super lucky. The bearings just destroyed themselves, but there's not too much coolant ingress. This is actually lucky, as far as we're concerned.

What's the worst-case scenario if it isn't caught early enough? The motor will flood in an unrecoverable way. Coolant gets into the stator, floods it out, and permanently destroys the laminations and the windings. At that point, it's basically a new motor.

Oh no, there was plenty of coolant in this motor. Oh boy.

Okay, let's see how this harness is. The harness doesn't look too bad—there's a little bit here. The connector has a lot of stuff on it. This is what happens when they leak—they flood with coolant, and a lot of times, they'll kill the electronics when it gets into this housing.

Again, I think this customer just got super lucky. Sometimes, this coolant can wick up these wires and actually rot out these cable ends and connectors. We'll pull this harness off and clean it to make sure there’s no corrosion. Worst case, we have all the components to build new harnesses. We can re-pin them, we can resolder connectors onto the board. But this control board looks okay.

This is the primary brain of the inverter. It drives the three power phases. You have your 400 volts coming in here, which is distributed to phases A, B, and C. That actually goes through the three-phase bars into the stator and makes the motor turn. This is the part that makes the horsepower—this is the actual power electronics.

This is a weird set of failures. Typically, the older generation ones had the better triple-lip seal but worse metal bearings. The later ones had a single-lip seal with ceramic bearings, which were bad in a different way. But occasionally, especially these Rev Qs, there's this horrible mix and match.

We've seen plenty of triple-lip Rev Qs, but this is a single-lip Rev Q. We're not quite sure what was going on in 2016 to 2018 when they were manufacturing these motors.

Yep, you can tell a decent amount of coolant has leaked in there. You can see it on the inverter housing.

We can see that there's some coolant ingress into the harness here. You can see all the coolant—it’s still wet. There's evidence of the glycol. What we're looking for are nice, shiny pins on the back of each of these connectors. It hasn't wicked up far enough to ruin these connectors, so we will not have to do a harness repair. We’ll simply clean all the existing coolant off, and it will be good to go.

A regular ohm meter is not sufficient to determine the insulation of systems operating at this kind of voltage. A normal multimeter only puts a couple of volts through the test. For insulation testing, we need to run much higher voltages. We're going to run 500 volts through and check the isolation. This is going to come up to above 100. If we were rebuilding this, this would be considered an excellent stator.

We want to see above 10—above 100 is excellent. It's going right up to 200, so this stator is in fantastic shape. We need to do nothing to it.

Beautiful.