Steps To Replace Alternator On 1998 Ls400

listener10 · December 11, 2010

I decided to post the steps for replacing an alternator on a 1998 LS400.

I’d only found instructions posted online for 1990-94 models and found it is similar, but there are additional significant steps for the 1998. Note, if you are going to replace your power steering pump on this car (apparently it is common the pump will leak and fry out the alternator), it looks like you would have to remove the alternator to be able to access the rear power steering pump bolts.

The alternator is somewhat hidden slightly below and to the right of the power steering pump on the passenger side.

1. Raise front of car, you will have significant under car work to do. The Wheels will not be in the way, so I just pulled up on Ramps.

2. Disconnect battery!

3. Remove the under-engine plastic cover. This is secured with about a dozen 12mm bolts (you will now be able to see the underside of the alternator)

4. Remove plastic cover / air intake assembly over the radiator.

5. Check to see you have the sticker showing the fan belt routing under your hood (if not, make notes), the remove the fan belt. This is simple using a 14mm socket with a 4” extension on the belt tension, rotate counter-clockwise to relieve tension and just slip off the belt.

6. You will need to remove the fan shroud in front of the engine to be able to have room to remove the Alternator, unlike the 90-94, there is not room to have it lowered out the bottom to the ground. The fan shroud is secured by 4 10mm bolts at each corner. There is a lower plastic baffle on the shroud that is just “clicked in”, remove this first. You also have to temporarily disconnect the driver side upper radiator hose to pull the fan shroud up and out – hold a rag under this to catch any spilling. It is a tight fit, but will come straight up and out with some wiggling. Put the radiator hose back on to avoid further spilling of radiator fluid.

7. You will need to remove the pulley off of the front of the Power Steering pump to be able to slide out the alternator. This is different than the instructions for the 90-94 LS’s. This was a challenge on my car. It can be easier to tackle this with the passenger side radiator hose removed, but you have more fluid to deal with. I gave in and disconnected the hose at the top to get more room. This is what worked for me:

a. Apply penetrating oil to the nut

b. To act as a brace, use a deep well ½” socket on a 2” extension, slide the socket through a hole in the pulley (they are similar size) and rotate the pulley counter clockwise until you can brace socket against the power steering pump housing, stopping the pulley from turning.

c. Using a long wrench or breaker bar with 17mm socket remove the nut (lefty-loosey / righty-tighty). This was not easy.

d. Once the nut is off, you still need to get the pulley itself off. It is friction fit. What worked for me was getting under the car with a very small ballpene hammer and tapping the back side of the pulley from below. Tap tap, turn, tap tap, turn…there was little room to do this, but it eventually came off.

8. Remove the alternator mounting bolt and nut. The 14mm bolt is on the bottom, it can be removed from below or above, just slightly easier from below. The 14mm nut is on the top, now that the power steering pulley is out of the way, this nut will be easier to remove.

9. You now need to release the cables from two cable clips attached to the alternator. On mine they were taped on. I carefully cut the tape. The cable clips themselves can be removed (one nut each) but that would be very difficult to accomplish while the alternator is still on the car.

10. You will have two wire sets to remove from the alternator working from below. The first is the “terminal B” heavier wire. Remove the rubber boot to access the nut. This was secured with a 12mm nut on the original, but my replacement had a 13mm nut.

11. To more easily remove the next wire set, you can now slide the alternator off the mounting post and rotate the alternator so you can access the wire connector. Remove the rubber boot. On one side (the outside edge) there is a little tab you can push in, then you can (with difficulty in my case) wiggle the connector off.

12. With alternator fully disconnect, lift out through the top of the hood.

13. Note the positions, and remove the two wire clips from the alternator. You will need to install these on the new unit.

14. When reinstalling, I used zipper ties instead of tape to again attaché the wires to these clips.

15. Assembly is the reverse. When putting back on the power steering pump pulley I found it difficult to brace the pulley to effectively tighten. I made a brace using a piece of oak hardwood with a hole for the wrench to slide through, and two lag bolts going through the wood but the protruding out far enough to catch the holes in the pulley to hold it in place. Yes, there is a special tool for this that I didn’t have. Putting the belt on first would add some friction but I’m not sure it would be enough to effectively tighten.

16. I was told to be sure the battery was charged before the first start with the new alternator to avoid stressing the diodes in the alternator. Not sure if this is true, but, I charged it up while I was doing the replacement.

This took about 4-5 hours for me to complete given some trial and error to figure out the extra steps vs the 90-94 model instructions and some stubborn bolts/connections. If I had to do it again, I could probably complete in 2-3 hours.