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1998 STS Aalternator


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I need to replcae my alternator on my STS. From what I can tell this is the original alternator. It only lasted for 142,000 miles..LOL

I did a search and couldn't find anything on how-to, etc.

No Haynes manual at store. :(

Please anyone done this before or has the iinfo they could share.



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Some things that I found helpful in changing out the alternator in the car are: a) removing the alternator access plate on the bottom of the car, over on the right side below the alt. It's approx. a 3" X 4" plate that is held in with a couple of bolts, I think; B) spin the nut off the front of the alternator with an impact and remove the pulley and cooling fan prior to dropping the alternator out the bottom of the car; and c) as a last resort you can remove the two front motor mount nuts and jack up the engine some to help facilitate removal of the alternator out the bottom. There is no way it will come out the top without removing a ton of brackets and hardware. It has to be taken out from below. Good luck!

The above quote is from Mechanix(Cadillac Forums)on how he removed his alternator.

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Since I have never replaced a generator on a '98+ Seville, I can't really offer any advice on how best to perform the job. However, I just accessed an online version of the GM service manual for your vehicle, and it advises removing the radiator and the A/C condenser before even removing any of the generator fasteners! Also, you need to be aware that the generator on '98 - '00 Sevilles (and '00 Devilles) is water cooled. So, even if there is a way to remove the generator without removing the two heat exchangers, as advised by the service manual, then you would likely have to drain the engine coolant, at least partially, before disconnecting the coolant hose on the generator and then removing the generator itself.

Maybe someone else who has actually performed this generator remove/replace job before will post a reply and paint a prettier picture than the one I described above. But, given the apparent difficulty of this job, and your lack of a GM service manual (as many other users of this Web site will attest, any "aftermarket" manual is a poor substitute to the proper GM manual), I'm inclined to suggest that you take your vehicle to a Cadillac dealer and have the work performed there. Furthermore, regardless of who actually performs the job, be sure to use the proper AC-Delco replacement generator -- again, as many other users of this Web site will attest, "aftermarket" generators (and many other parts) for late-model Cadillacs are notoriously unreliable!

Good luck!

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This will take all day if you have never done it before.

1. Disconnect battery negative terminal.

2. Remove top plastic radiator cover.

3. Remove both Headlights - Remove two 10mm bolts from top of headlights and pull lights STRAIGHT forward to disengage the rear headlight support. If you are not careful you will break the rear support. You may want to use a screwdriver and insert it where the back of the headlight meets the fender (where the turn signal is) and pry the headlight forward. Remember to protect the paint with tape or something while you pry.

4. Drain Radiator.

5. Remove hood latch and place on top of engine, out of the way (you will also have to disconnect the air temperature sensor that is mounted on hood latch).

6. Remove top radiator hold down brackets (10mm).

7. Pull the radiator up to disengage the center radiator supports and slightly pull the radiator forward. It will not want to come at this time because all the hoses are still connected.

8. On the top right of the radiator (drive side) there is a transmission cooler line with a quick-connect fitting. Use a small screwdriver to carefully push back (away from the radiator) the white plastic collar to expose the spring clip. Now, you must remove the spring clip with the screwdriver (careful not to loose the spring clip or you will be visiting the dealer). Remove the 10mm bolt that secures the oil line to the radiator and carefully pull out the oil line and move it out of the way.

9. Use pliers to compress the lower radiator hose clip (just under the oil line you removed) and remove the lower radiator hose from the radiator and move it out of the way.

10. Remove the upper radiator hose from the engine and move it out of the way.

11. Pull the radiator forward a little further.

12. There is a plastic clip between the two fans that supports the A/C return line. Use a long screwdriver to carefully disengage and open the clip. Now, bend the aluminum A/C return slightly line away from the fan shroud.

13. Remove the two 10mm screws that fasted the fan shroud to the radiator.

14. On the bottom left of the radiator there is a 3/8” water line that feeds the alternator. Compress the spring clip and remove this hose (or cut the hose).

15. Push the top of the fan shroud away from the radiator and lift it to disengage the lower fan support and wiggle the fan shroud up and out of the car (remember to disconnect the two fan motor harnesses). You will need to angle the fan shroud a little to clear the bottom right trans cooler line.

16. Now you can pull the radiator further forward and access the alternator from the gap between the radiator and upper frame.

17. Disconnect the red cable at the back of the alternator (10mm).

18. Disconnect the wiring harness at the back of the alternator.

19. Remove the serpentine belt.

20. Cut or remove the coolant lines that enter the back of the alternator.

21. There are three 15mm bolts holding the alternator in place. One is at the front of the alternator (passenger side) and two are at the top-side of the alternator (front of car). One of the bolts also has a ground wire.

22. Remove the bolts and pull the alternator out from behind the radiator.

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The manual says to remove the radiator. However, you don't have to do this. If you have a lift, great, but it can be done on jacks. You will have to discharge your

AC system, remove the AC compressor, and then remove the alternator from below. The bolts are hard to get to but it beats removing the radiator. Of course you have to be knowledgeable about AC systems and have access to the proper equipment.

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Hmm, I figured that the alternator replacement on the G body Seville would be like on the Aurora. I changed the alternator on the aurora and did not have to remove the radiator. I did have to take out the radiator fans and disconnect a few of the hoses on the radiator.

It was a real pain, much harder than my 97 - but can be done in a few hours once you know the procedure.

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