Pelican Technical Article: Alternator Replacement Wayne R. Dempsey
Time: 4 hours
Tab: $400
Talent:
Tools:
Socket set
Applicable Models:
986 Boxster (1997-04) 987 Boxster (2005-08)
Parts Required:
New alternator, new drive belt
Hot Tip:
Tap the inside bushing to release it from the bracket.
Performance Gain:
Consistent charging output
Complementary Modification:
Replace drive belts
This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your Porsche Boxster. The book contains 312 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 950+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Boxster owner's collection. The book is currently available and in stock now. See The Official Book Website for more details.
Check out some other sample projects from the book:
One of the nice things about the configuration of the Boxster engine is the relative ease with which you can replace the alternator. The alternator is nestled neatly on the right side of the engine compartment: very easily accessible. The replacement and repair process is straightforward, and should take you about an afternoon to complete.
The first thing that you need to do is to make sure that your alternator is indeed the cause of the problems with your charging system. Sometimes bizarre electrical problems can be caused by a number of faults other than the alternator. It's important to troubleshoot the system prior to replacing your alternator.
The first thing to check is the belt that drives the alternator. Is it tight and amply turning the alternator pulley? If it's worn or close to breaking, then replace it and recheck the alternator (see Pelican Technical Article: Drive Belt Replacement). Modern belts seldom break, but they get brittle and glazed with age, and can slip on their pulleys.
The next item to check is the voltage at the battery. This should read a little more than 12 volts with the engine off. When the car is running, the voltage should read at in the range of 13 to 14.5 volts with the engine at 2000 rpm. If your battery appears to be leaking, then your alternator's voltage regulator has probably failed. The battery will usually only leak acid if it has been overcharged at a much higher voltage. If the voltage measured at the battery is more than 16 or 17 volts when the engine is running, then the regulator is probably bad. If your battery has boiled over and has acid overflowing out the top, make sure that you clean up any spilled acid immediately. Dousing the area with a water and baking soda solution should help considerably to neutralize the acid, and prevent it from eating away at the metal.
An important item to check on your car is the engine ground strap. The engine is electrically isolated from the chassis by rubber motor mounts. If the engine ground strap is missing or disconnected, then you might have a whole bunch of problems, including electrical system malfunctions and difficultly turning over the starter. See Project 81 for the exact location of this ground strap.
The first step is to remove the belt that drives the alternator. Refer to Project 5 for detailed instructions on the belt removal. Removing the alternator from its bracket itself is a relatively straightforward process. Start by loosening the large B+ cable that is located inside the top of the engine compartment. See Project 3 for instructions on how to access the engine compartment.
Now, loosen but do not remove the lower alternator bolt (green arrow, Figure 3). Then, loosen the idler pulley that is located next to the alternator. Loosen the bolt and back it out about 3-4 full turns. Then, using a drift and a hammer, tap on the bolt. The purpose for doing this is to loosen up the metal bushing that is located inside the rear flange of the alternator. With the bushing loose, lift up on the idler pulley, and the alternator assembly should rotate counter-clockwise. Remove the lower bolt, and the alternator should be able to be lifted up and out of the engine.
On this particular car, this bushing was a tight fit and required quite a bit of tapping, and quite a bit of wiggling to remove. Specifically, I had to use a very long drift to tap directly on the rear bushing to get the assembly loose. Other mechanics seem to indicate that this is a common problem, so you might have to work at it a bit to get your alternator out.
If you are replacing the alternator completely, then the installation of the new alternator is simply the reverse of the removal process. Make sure that you reconnect all of the wires to their proper terminals when you are done. If you're still not sure if your alternator is bad, you can take it to any good auto parts store, and they should be able to test it for you for a modest fee.
Figure 1
Shown here is a brand new rebuilt alternator. Unlike older-style Porsche alternators, this one is pretty much plug-and-play. The regulator is internal, and the alternator should come with the proper pulley installed on the front. The green arrow in the inset photo shows the metal bushing that may give you trouble when you try to remove the alternator. This bushing is the one that needs to be tapped on in order to loosen the assembly for removal.
With the top of the engine compartment open, loosen and disconnect the cable that attaches to the alternator. This will allow you to pull the unit out and away from the engine compartment.
You can access the alternator assembly through the engine compartment access panel behind the seats. Simply loosen both mounting bolts. Turn the idler arm bolt back about 3-4 turns.
Using a metal drift or punch, tap on the bolt to push out the rear metal bushing. This may require some significant tapping. If the bushing is stuck, you may end up damaging the idler pulley bolt. Don't fret though, as a new one is only $5.
With the alternator disconnected from its bracket. Pull the unit out of the engine bay and disconnect the two electrical connections on the rear (blue and red arrows).
Comments: Just completed the alternator replacement. One warning that would have been helpful...don't start the engine with the passenger seat removed. I did and now the airbag warning light is illuminated. Any way to clear the fault without a trip to dealer?
March 10, 2012
Mickey
Comments: I just replaced the alternator on my Cayman S and there are a few differences from the Boxster article. First, there is absolutely no acces to the alternator from the upper engine access panel - it all has to be done from behind the seats. Second, it's not a simple bolt but a star bolt and you need a particular socket to get both of the alternator bolts off. The longer one butts up against the bulkhead to you really have to finesse the bolt out.
December 25, 2011
Followup from the Pelican Staff: Thanks for the updated info! - Wayne at Pelican Parts
Brian
Comments: Yeah, just need to hammer away on the bolt with the bushing. I ended up making a video http://youtu.be/jUjJqK8qJDE. Thanks Wayne, your parts and instructions were spot on.
November 11, 2011
Jos V.
Comments: I just replace my alternator. The hardest part is to push out that bushing connected to the roller's bolt. I followed Wayne's instruction. After an hour, there is no luck so what I did is I totally removed out the bottom bolt. Spray the bushing with oil and used my breaker bar or any solid steel bar and pried up the alternator against engine block. It worked.
November 10, 2011
Followup from the Pelican Staff: Thanks for the tip, these can indeed be a bear. I don't know who's the genius who designed this, but it doesn't work very well. - Wayne at Pelican Parts
Wayne at Pelican Parts
Comments: If you have a problem with your alternator, it may be the decoupler pulley, which is a special pulley that is installed on the alternator that allows it to spin up when the engine is accelerating, but free-wheel rotates when the engine is decelerating. This is because the rotating mass of the alternator will work against the belt when the engine is decelerating and can cause premature belt wear. I found this neat video online here from Gates, a well-respected belt manufacturer: http://www.youtube.com/watch?v=hrFcPqZuO3A&feature=related
October 18, 2011
Brian
Comments: I am having a devil of a time getting this alternator out. I have hit and hit the bolt with a punch, the bushing doesn't move. I am able to get the bolt almost out of the housing, it hits the firewall and I'm afraid the force it. Any other ideas on how to get this thing out?
October 5, 2011
Followup from the Pelican Staff: See the comment above here. It's a bear to remove, you just need to keep working at it. - Wayne at Pelican Parts
Thomas
Comments: I have a Cayman, is the process the same?
And does it matter to have a manual or tiptronic alternator? I have a six spped manual
August 4, 2011
Followup from the Pelican Staff: Yes, the process should be almost exactly the same, with the only exception being how you access the top of the engine of course. - Wayne at Pelican Parts
Nathan
Comments: The bushing on my 2002 Boxster S was rusted solid. I was able to get the alternator out. It would have been easier if this bushing had loosened. I have attached a photo of a bushing that HAS NOT been tapped back out of the way
July 14, 2011
Followup from the Pelican Staff: Indeed, as you have seen from the comments here, this is a terrible design. Thanks for the informative photo! - Wayne at Pelican Parts
Jerry
Comments: Thank you so much for the article. I found it necessary to punch the back bushing even further than just loose, to maybe 1/18 inch. Then remove the long bolt. This allowed me to slip a small thin steel pry bar between the engine and alternator to balance the alternator while I rotated it clockwise. Both in and out were a breeze with the back alternator bracket fitting easily under the engine mounting bracket both in and out. The key tool that helped me the most the heavy duty paint finish remover tool that helped balance the alternator and minimize finish damage to all parts involved. Secondarily, I worry about future replacement due to the Bosch Bushing design. I did not do a metal analysis and so maybe it will be of no concern. However, rust, corrosion, whatever, does happen and I visualize the bushing spinning once corrosion starts on the bolt threads. Maybe a light thread surface treatment would be helpful for the next alternator replacement. 20-20 hindsight: Id suggest a protective cloth to cover both the engine front and firewall. The alternator hits the firewall while the electrical connectors are removed and removes the paint on the edge of the firewall. That will rust out at the edge.
Thanks again for the article. Its first Porsche Ive worked on and never been beaten by an alternator. But this one came as close as any.
Thanks again for your help
Jerry
June 14, 2011
Followup from the Pelican Staff: Thanks for the tips. I don't know who designed this alternator setup, but I think they should probably be fired in my opinion. - Wayne at Pelican Parts
Jim
Comments: Where does the metal bushing of the alternator connect to or go when you tap it out. Does the idler pully have to be completely removed?
November 24, 2010
Followup from the Pelican Staff: It's hard to explain - the bushings doesn't really pop out - it's embedded into the alternator bracket. You're just loosening it up a bit so that you can get the alternator out. It's a bit of a goofy design. - Wayne at Pelican Parts
Check out some other sample projects from the book:
