Step-by-Step Installation of ReVolt Systems’ Coolant Bypass Kit for Tesla LDUs

How to Install the ReVolt Systems Rotor Seal Bypass Manifold

About four years ago, the team at ReVolt Systems noticed the rear seal failing in a few Tesla Model S Large Drive Units (LDU). Now it’s upwards to about 30+% and on the rise as these motors see higher mileage. A lot of these earlier models are now falling out of warranty and Tesla charges over $6K for a replacement, which also has the potential to leak. So ReVolt Systems developed a kit that addresses these notorious rotor seal issues present in all Tesla LDUs s , drastically extending the life of your motor.

ReVolt has seen the problem develop anywhere between 25k miles on up, so there’s a very wide window of failure, and if you have a Tesla LDU it’s not a matter of “if” it fails, but “when.”

The cause of these failures were due to the seal and sealing surface degrading, allowing coolant to leak into the stator windings and inverter causing isolation issues, inverter failure, and in some cases complete motor seizure. If the rotor seal has not yet leaked, this kit will eliminate all risk of rotor seal failure in the future. ReVolt calls the solution to this catastrophic issue the “Achilles Seal” fix, AKA the Coolant Bypass Kit.

Let’s walk through the installation process together.

**01.** With the LDU removed from the vehicle, first remove the three 10mm bolts securing the external coolant line and remove the coolant line.

**02.** Remove the two 10mm bolts securing the encoder and coolant fitting and remove both components from the LDU. These components will be re-used.

**03.** Remove the six 10mm bolts securing the rotor seal manifold.

**04.** Use a pry-bar to carefully remove the rotor seal manifold. There are two convenient pry points shown in these photos, but take care to pry it off evenly and as square as possible to the drive unit.

**05.** A small amount of coolant will be present when the manifold is removed. If you find rust and corrosion on the encoder wheel and rotor bearing, this is an indicator that the rotor seal is already failing, and you should contact a professional to diagnose any additional damage to the internals of the motor

**06.** The two lower bolt holes are usually full of silicone from factory assembly. Use a 5mm drill bit by hand to remove the silicone from these holes. Do not use a power drill as you risk damaging the threads. Inspect the O-ring on the drive unit and ensure it is free from any debris and that it is seated in its groove.

**07.** Apply a thin bead of silicone sealant around the new rotor seal bypass manifold as shown. Apply a thin film of O-ring grease to the new Rotor seal bypass manifold.

**08.** Install the new rotor seal bypass manifold, taking care to seat it correctly the first time to avoid dislodging the O-ring.

**09.** Loosely screw in all the 10mm bolts. Once all bolts are in position, torque them to 8Nm in a crisscross pattern.

If the bolts start to get tight before they are fully seated, STOP, and see if the bolt hole still has old silicone stuck in it. These threads are easily stripped, especially the lower two.

ReVolt has seen the problem develop anywhere between 25k miles on up, so there’s a very wide window of failure, and if you have a Tesla LDU it’s not a matter of “if” it fails, but “when.”