Lexus GS450h Transmission Oil Pump Bearing Replacement
Unlock the car and disconnect the 12v battery for safety and to clear any fault codes. I also took the opportunity to run my HV battery conditioner (courtesy of Richard at Hybrid Battery Solutions) while the car was laid up:
Put the car up on a ramp or over a pit or, worst case scenario just get it as high as you can safely. I used four axle stands and thin blocks of MDF/wood to protect the side jack points, and the lifting was done one end at a time with trolley jacks under the front crossmember and rear transaxle casing, again protected by MDF blocks:
Front view. The long piece of cardboard was free and invaluable for sliding under and out from the car without wearing out my backside or the back of my head! And for catching some oil drips. You might have a proper runner or something better:
10mm socket used to undo the long plastic cover under the transmission. You may find other fittings such as cable ties and string, especially if your cover has sustained some damage over the years! Mine had!:
Make sure the exhaust is cool then remove the bracket going across from the two exhaust pipes and under the transmission. Two nuts from the transmission:
Then a nut and bolt each from the exhaust flanges:
And remove the bracket:
Here on the driver's side of the transmission, you see the cylindrical black motor of the transmission oil pump:
Here's a better view showing the grey pump section at the front and at least one of the four bolts holding it to the transmission. Before you take this off you need to:
Drain the old transmission fluid by removing this plug in the recess of the bottom pan:
But have your oil tray ready of course!:
Once drained, replace the plug to stop drips and remove the four bolts for the pump. Access to the top two is tricky so have plenty of tools to try. I used 1/4" sockets (12mm I think?) and a T bar but you might find an offset ring spanner gets in there better:
The pump should drop down a bit but there's a strong set of cables and clips holding onto it. Avoid losing the gasket. Also note a small rubber pipe (drain?) which comes down above the pump and is a push fit onto a spigot on the top of one of the pump flanges. Pull that off:
Loosening a few cable clips I was able to lower the pump enough to work on it comfortably, but you may prefer, as Hayne, to detach the cables all the way back up through the engine bay and unplug the connectors to get the whole assembly off the car.
Use an allen key to undo the bolts (mine were stiff but not seized) holding the motor front plate to the impeller housing, then remove the impeller housing, preserving the big O ring between them:
Removing the remaining bolts and the allen screw holding the single black earth cable freed up the motor front plate and the magnetic rotor with front and rear bearings:
The front bearing inside the housing was fine. If your front bearing is bad you might prefer to go back to the engine bay and get out the whole cable to take the whole thing to the bench. You can see from the colour of my rear bearing it looks scorched and it was also stiff to turn:
A wooden mallet, or a piece of wood to protect the front shaft of the motor while you tap it with a hammer, should free the rotor assembly from the front plate and bearing. If you have the whole thing off you have the option of using bearing pullers or whatever you prefer:
On the bench it's pretty simple job to pull off the back bearing and replace it. The rotor is a magnet so keep it clean from stray fragments of metal which might end up living in your motor and killing it again:
A cleanup and a smear of white silicon grease on the bearing casing to aid reassembly. If you want to replace the front bearing it will be easier to take the cables and motor front plate off the car. You will need to undo three screws securing the rotation sensor, then push out the bearing and replace it. Mine was fine:
Reassembly, as the Haynes manual would say, is the reverse of disassembly. Make sure everything is clean, particularly the gasket, seals and the rotor. Be careful of rear bearing damage when tapping the rotor back into the front bearing. Keep the rotor central as you push it back into the motor body and seat the rear bearing. Rotate the motor front cover to align the earth cable and screw holes. Make sure the rotor is free to spin with the motor back together. Fit the pump back on the motor with the O ring. Then the pump goes on the car with the clean gasket, reconnect earth, (drain?) pipe and refit bolts, probably the fiddly top ones first. Tidy and clip your cables well away from the exhaust.
Make sure the sump plug is tight and recheck everything else you have touched. Refit the exhaust bracket. Remove the oil fill plug on the side of the transmission. I filled with fresh ATF, (messy process), until the oil was seeping back out of the top hole. It used about 4L. Then refit the plug. Clean up everything especially any visible oil. I disconnected my HV battery conditioner but you likely won't be using one. Reconnect the 12v battery. I started and ran the car for 15 minutes while I checked for new fault codes with my Mini VCI and TechStream. Check for leaks.
Reset the security and steering sensors. Open drivers door, wind window fully down and back up. Should hear (3?) beeps. Repeat for the other three doors. Similar for the sunroof I think. Wind steering fully left and then right and repeat a few times and then back to centre. Then shut it down, let things cool. Final leak check. Put your bottom cover back on. Get it back on it's wheels.
Done!
