W116 115-amp Alternator install - PeachParts Mercedes-Benz Forum

thesst · #1 07-13-2008, 09:00 PM

How the heck do you get this thing to fit? I can get top and bottom bolts on but then it won't move in far enough to slip the belts on.

Any ideas/tricks/tips on doing this install in a W116?

Thanks.

Diesel911 · #2 07-13-2008, 09:43 PM

Maybe you need longer belts.

yellowbenz · #3 07-13-2008, 09:44 PM

There should be a third bolt to loosen. That should allow it to pivot enough to slip on the belt.

thesst · #4 07-14-2008, 06:54 AM

Where is this third bolt?

yellowbenz · #5 07-14-2008, 07:27 PM

Bent my alternator bracket - should I be worried?

check out post 14 on this thread. Bottom picture should show the third bolt that connects the upper bracket to the block. You may have a slightly different set up if you don't have the york compressor. Probably covered by alot of dirt. May need to pb blast it before loosening.

300SD81 · #6 07-14-2008, 07:45 PM

If you have a 617, make sure you don't forget the tube/long washer thing on one of the bolts, you will bend your bracket... and its a real pain to un-bend.

I need to do this upgrade again on my new car, voltage was bottoming out on the trip home with my laptop running (rated 8A at 18.5V, draws more occasionally, so 13A at 12V if the inverter/transformer combo was 100% efficient)...

pawoSD · #7 07-14-2008, 11:46 PM

My alternator has been "strange" for quite a while, its a 1.2 year old reman bosch unit (65A) it sounds like banging cans and you can feel the grinding when you touch the casing while its running...

But....its been doing it for thousands of miles without failing.....we'll see if it does.

When it does I am going the full power 115A route as well, I would not mind the extra juice. If I can find a good job sometime soon I will likely just replace it before winter comes (along with my wiring) so I can run ALL I want (blower, defroster, fog lights, headlights, etc...) at idle in the snow/cold without it bogging down to 11V.....my afterglow system kills the voltage for a couple mins too....

DEB1979MB300SD · #8 07-15-2008, 01:38 AM

Here is info I saved on my computer when I had to change my alternator out. I would like to give credit to original poster but did not save that info.

Exploded picture of alternator
http://i331.photobucket.com/albums/l459/dkkuhnphotos/Alternator.jpg
"Let make sure your loosening all the correct bolts.

Look at the parts diagram below.

One note, first, Bolt #89 and 86D are now a one piece welded bolt.

At the rear of the alternator you are going to loosen 3 bolts/nuts.

The bolt head of #81E which goes into a mounted nut on the upper bracket #78 ( this is a pivot bolt for the upper bracket, which must pivot while loosening )
The nut at the rear of bolt number 73D ( this is the pivot bolt for the alternator)
The nut to bolt 86D, not shown (this is a clamping bolt on the upper part of the alternator)

Once all three bolts/nuts are loose you rotate nut # 79 to loosen the alternator belt by moving the alternator towards the center of the car. Once move enough the belt can be removed.

I recommend Mercedes belts. I got Gates belts for my daughter’s car and have had problems with all three.

Now if your bolts are rusted PB blaster is the best. If not all 3 are loose, then it will not budge."

On my 1st 79 MB 300SD (aka Rusty) I broke head off bolt

even after soaking with PB blaster several times for two days. 2nd one needed alternator rebuilt & had no trouble at all removing and reinstalling it. Good luck.

thesst · #9 07-15-2008, 03:19 AM

Quote:

Originally Posted by DEB1979MB300SD

Here is info I saved on my computer when I had to change my alternator out. I would like to give credit to original poster but did not save that info.

Exploded picture of alternator
http://i331.photobucket.com/albums/l459/dkkuhnphotos/Alternator.jpg
"Let make sure your loosening all the correct bolts.

Look at the parts diagram below.

One note, first, Bolt #89 and 86D are now a one piece welded bolt.

At the rear of the alternator you are going to loosen 3 bolts/nuts.

The bolt head of #81E which goes into a mounted nut on the upper bracket #78 ( this is a pivot bolt for the upper bracket, which must pivot while loosening )
The nut at the rear of bolt number 73D ( this is the pivot bolt for the alternator)
The nut to bolt 86D, not shown (this is a clamping bolt on the upper part of the alternator)

Once all three bolts/nuts are loose you rotate nut # 79 to loosen the alternator belt by moving the alternator towards the center of the car. Once move enough the belt can be removed.

I recommend Mercedes belts. I got Gates belts for my daughter’s car and have had problems with all three.

Now if your bolts are rusted PB blaster is the best. If not all 3 are loose, then it will not budge."

On my 1st 79 MB 300SD (aka Rusty) I broke head off bolt

even after soaking with PB blaster several times for two days. 2nd one needed alternator rebuilt & had no trouble at all removing and reinstalling it. Good luck.

My god man you are a lifesaver! Thank you very much!

Great info, very much appreciated I will give all this a try tomorrow.

DeliveryValve · #10 07-16-2008, 12:14 AM

Quote:

Originally Posted by pawoSD

My alternator has been "strange" for quite a while, its a 1.2 year old reman bosch unit (65A) it sounds like banging cans and you can feel the grinding when you touch the casing while its running...

But....its been doing it for thousands of miles without failing.....we'll see if it does.

.......

Make sure you have some shoe strings with you and a knife or maybe some tools to remove the belt from the alternator. Because there is a possibility that the alternator will eventually seize and will seize up the whole motor while your on the road. I had this happen to me and I used my shoe string trick to get me 10 miles back home. It part of my emergency kit.

300SD81 · #11 07-16-2008, 03:42 AM

I've always wondered if it would be a good idea to run one belt over the water pump/crank only and a second in the original config. That way, if you ever have alternator trouble, you'd still have the water pump... Happened to me once 400 miles from home, thankfully, it didn't seize, but driving 400 miles with no electrics and half an hour of rain with windows stuck open does kind of suck too...

thesst · #12 07-23-2008, 02:39 PM

Update: it fits perfectly. Thanks again to DEB1979MB300SD for the helpful information.

So it's official then: the AL129X 115 amp alternator works in:
W123
W116
(anyone tried it in a W115 or W126?)

300SD81 · #13 07-23-2008, 03:49 PM

Quote:

Originally Posted by thesst

Update: it fits perfectly. Thanks again to DEB1979MB300SD for the helpful information.

So it's official then: the AL129X 115 amp alternator works in:
W123
W116
(anyone tried it in a W115 or W126?)

Drops in as easily as the stock one comes out on a W126.

pawoSD · #14 07-23-2008, 04:54 PM

The alternator locking up won't lock up the engine, it will smoke the belts. My dad had one lock up, the starter was actually strong enough to re-start the engine with the alternator seized!

Needless to say, the replacements included two new belts + alternator.

I too have thought of a setup that had one belt to the water pump and one to the alt....but, how would you tension the water pump belt?

I recently swapped mine out with a better one. The old one was junk. Last time I am cheap and use a McParts alternator. (Malaysia) The little resistor in the voltage regulator fell out in my hands when I removed it to check it! Not to mention about 75% of the brushes were gone! And it was only a year old!!

Bearings were shot too, the rotor had all kinds of play in it sideways. I put in a German Rebuilt Bosch, way better.

Eventually I will upgrade if I can find one of those AL129x units for a good price and in good shape. So far the german 65A is doing a good job though. It even has a German voltage regulator (with 90% of the brushes left)

DeliveryValve · #15 07-23-2008, 10:32 PM

Quote:

Originally Posted by pawoSD

The alternator locking up won't lock up the engine, it will smoke the belts. My dad had one lock up, the starter was actually strong enough to re-start the engine with the alternator seized!

Needless to say, the replacements included two new belts + alternator.

....)

Well I must have a weak a$$ engine. Because it kept dying in idle. OK maybe it doesn't fully lock up, but it will definitely make a bunch of noises and smoke as you raise the RPM a bit.