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  #16  
Old 12-23-2007, 03:45 PM
Emu Rancher
 
Join Date: Mar 2002
Location: Washington, DC
Posts: 664
I finally got started today. I've got the power steering belt out but haven't started with the alternator. I'm assuming all of the bolts and hardware are on the inside of the alternator facing the back of the car. Is this a pain to get to. I'm 6'9" and try to work from the top of the car as much as possible. Also I want to doublecheck my belt sizes. I have a pair of toothed belts pn A 004 997 85 92. I'm assuming these are for the alternator but they are the 1000mm in length. I have two smooth belts one is A 004 997 93 92 at 997 mm. the other is A 004 997 99 92 at the same 997 length. Are these for AC compressor and power steering pump? The belt that just came off my power steering pump was toothed with makes me wonder if the dealer gave me the right belts.

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W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.
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  #17  
Old 12-23-2007, 06:12 PM
crashone's Avatar
1983 300SD, 4 speeed
 
Join Date: Jul 2006
Location: Raleighish, NC
Posts: 664
You should have 3 different size belts, 2 are the same size smaller (they work on the alt.) 1 is a little longer it works on the AC, the longest one is for the power steering. Sorry I don't have part numbers or actual measurements this is from my feeble memory. It is a bit easier to get to the bolts etc. on the alternator from under the car, just put it up on ramps and you will have plenty of room. You will be crawling up and down anyway changing all the belts. Insted of replacing the whole alternator you can replace the voltage regulator in 5 minutes. Make sure you have the correct amp alternator for your car. The 300SD uses a 65 amp where as the 300D uses a 55 amp. It will make all the difference in performance. Good luck.
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1983 300SD, 4 speed
1994 C280
1987 300TD wagon
1996 HD Road King

Ride in Peace Eric Peterson, Harley of Macon
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  #18  
Old 12-23-2007, 07:26 PM
Emu Rancher
 
Join Date: Mar 2002
Location: Washington, DC
Posts: 664
Thanks crash, The voltage regulator was replaced a year or two ago so it should still be good. I wasn't planning on changing the alternator but I might pull it and get it tested at autozone while I am down there.
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W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.
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  #19  
Old 12-23-2007, 07:38 PM
crashone's Avatar
1983 300SD, 4 speeed
 
Join Date: Jul 2006
Location: Raleighish, NC
Posts: 664
Autozone can check the alt while the motor is running. They will see how much volts/ amps are being put out. Juust drive it down there and have them hook up their gauges.
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If it ain't broke take it apart and find out why.

1983 300SD, 4 speed
1994 C280
1987 300TD wagon
1996 HD Road King

Ride in Peace Eric Peterson, Harley of Macon
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  #20  
Old 12-23-2007, 08:42 PM
Registered User
 
Join Date: Dec 2007
Location: Roswell, New Mexico
Posts: 82
Chasing this for months

I have had EXACTLY the same scenario in m 83 300D TD for 6 months - 3 new batteries, 3 new alternators, belts/tension checked, etc. and then ultimately the search for a short. I am NOT at all mechanical and have used this site to help direct locally very incompetent mechanics (first thing people tell you in Roswell, NM - DON'T get your car, or anything for that matter, fixed here). I have been told that the "short" was somewhere in to the stereo and several other places. I have been told "Oh, I definitely fixed it this time." Pattern is simple: new battery, trickle charge, whatever, it works for a couple weeks of short local driving and every time I take it for a 160 mile roundtrip to one of two clinics I work in outside of Roswell and on the way home the battery light starts to fade in and out and all the above shi*T starts happening. It will start for another day or two and then, that's it. We're down to jump starts for awhile and then - another new battery. Latest alternator is still good. Yesterday my landlord's son (mechanical guy - ex-Lexus mechanic) and I found some wires dangling below and just behind the bumper - he said they went to the temperature-control system - frayed and in contact - he just separated them and taped them up and stuck them up in the engine compartment. Really wish I could get this problem fixed once and for all.
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  #21  
Old 12-24-2007, 07:14 AM
toomany MBZ's Avatar
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Join Date: Nov 2006
Location: central Va
Posts: 7,820
Quote:
Originally Posted by adiaw83 View Post
I finally got started today. I've got the power steering belt out but haven't started with the alternator. I'm assuming all of the bolts and hardware are on the inside of the alternator facing the back of the car. Is this a pain to get to. I'm 6'9" and try to work from the top of the car as much as possible. Also I want to doublecheck my belt sizes. I have a pair of toothed belts pn A 004 997 85 92. I'm assuming these are for the alternator but they are the 1000mm in length. I have two smooth belts one is A 004 997 93 92 at 997 mm. the other is A 004 997 99 92 at the same 997 length. Are these for AC compressor and power steering pump? The belt that just came off my power steering pump was toothed with makes me wonder if the dealer gave me the right belts.
Check post #10.
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84 CD
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  #22  
Old 12-24-2007, 03:30 PM
Emu Rancher
 
Join Date: Mar 2002
Location: Washington, DC
Posts: 664
I'm working on loosening the bolts on the alternator. I got the large pivot at the bottom of the alt loose but I am struggling with the adjustment bolt. i dont have ramps but I can fit under the car and I've tried from down there and from the top with the assembly going from the turbo to the air cleaner removed. Is there another way to get to it?
__________________
W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.
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  #23  
Old 12-24-2007, 10:59 PM
Newguy's Avatar
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Join Date: Jul 2006
Location: N.E. Colorado
Posts: 98
You have to loosen all 3 bolts in the alternator.
The one closest to the block has a nut on the front, requiring a wrench on the front and the back of the bolt.
The one on the top left (furthest away from the block) has the tensioning bolt attached to the front of it. Loosen the head of the bolt from behing the alternator. You already have the 3rd bolt loose, which is the only bolt requiring you to get under the car.
Once all 3 are loose, you can turn the tensioning bolt CCW to loosen the belts.

Do it all in reverse when the belts have been changed out.
Good luck.
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1980 300SD W116 - Daily driver. 362,800 miles and counting. (about 100 miles / day) -- on hold, have a ticking vacuum pump. New one on the way.
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  #24  
Old 12-25-2007, 05:58 PM
toomany MBZ's Avatar
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Location: central Va
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Quote:
Originally Posted by Newguy View Post
You have to loosen all 3 bolts in the alternator.
The one closest to the block has a nut on the front, requiring a wrench on the front and the back of the bolt. This is the one I bent my ratchet on, way too tight.
The one on the top left (furthest away from the block) has the tensioning bolt attached to the front of it. Loosen the head of the bolt from behing the alternator. You already have the 3rd bolt loose, which is the only bolt requiring you to get under the car.
Once all 3 are loose, you can turn the tensioning bolt CCW to loosen the belts.

Do it all in reverse when the belts have been changed out.
Good luck.
I'll wish you good luck also.
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1983 300SD electrical problems-file-108.jpg  
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Last edited by toomany MBZ; 12-25-2007 at 05:59 PM. Reason: more info
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  #25  
Old 12-25-2007, 06:14 PM
Emu Rancher
 
Join Date: Mar 2002
Location: Washington, DC
Posts: 664
That's not going to be fun. Were you able to finally get that out from the top or were you working under the car?
__________________
W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.
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  #26  
Old 12-25-2007, 06:57 PM
toomany MBZ's Avatar
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Join Date: Nov 2006
Location: central Va
Posts: 7,820
Quote:
Originally Posted by adiaw83 View Post
That's not going to be fun. Were you able to finally get that out from the top or were you working under the car?
I was able to do all except that bottom bolt you have gotten to from the top. Move the fan around to gain access from the front. I put an open end on the back, and used that ratchet with a cheater bar, took about all the strength I had, chest hurt for awhile afterward, OK now. ALL the bolts were on too tight. I removed the turbo "U" tube while working on it. Be very careful with the adjusting "L" bolt, easily damaged, and expensive to replace.
If you have the chance, once the belts are removed, take to a parts store and measure to get the proper length.
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  #27  
Old 12-27-2007, 01:18 PM
Emu Rancher
 
Join Date: Mar 2002
Location: Washington, DC
Posts: 664
I have all of the old belts off!! It was much easier once I got an open ended ratchet wrench. I only had to get under the car and loosen the pivot bolt. Remove the U shaped tube from the turbo and air cleaner. Use the open ended ratchet on the adjuster bolt and loosen. Once this is loose, use a ratchet on the adjusting L shaped bolt to adjust the position of the alternator and remove the belts. I did not have to do anything to the third bolt which is next to the adjustment bracket. My pulleys are showing some signs of oxidation. I little rust has formed on the inner edges of the pulley. How should I prep them before attaching the new belts? Thanks for all of the help. Once I finish up, I'm going to write up a guide on changing the belts.
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W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.
Reply With Quote
  #28  
Old 12-27-2007, 05:51 PM
bulletproofair's Avatar
bulletproof air
 
Join Date: Sep 2007
Posts: 87
I'm curious to if you've finalized the problem being belts? The gauge jumps and strange elec. problems sound like ground problems I've experienced. Usually the ground problems are the same as low battery problems as well. It could obviously be the belt, but if you have the belt tight and its a decent belt at the least, as long as its cranking the alternator there really shouldn't be a problem...make sure you don't overtighten while you're at it though.

Just thought I'd chime in, as I think one person mentioned it might be a ground problem and I just wanted to say that grounding issues really aren't that rare to come across from what I've experienced with these diesels.

There is a ground strap that goes to one of the two bolts that hold the starter to the bellhousing. Sometimes it gets rusted out or may have built up crud over the years if you haven't messed with your starter. Also, the ground battery cable that leads to the battery is rather short and goes directly to the hood spring bracket. The bolt holding it down may have come loose from installing and removing batteries because of moving the cable around to fit it on the battery. Its worth a check at least, if you haven't solved your problem that is.

Anyway, you can CHECK your alternator's output by using a multimeter in volts at the battery. Just check it while your car is running opposed to when its off, and it should be putting out around 14V. A little less is probably normal. Anyway, this will help narrow down the source of your problem. I agree with "crashone" you should take it to autozone and get the amperage tested as well. If you have a nice meter you can do it with your meter, but I believe autozone's machine puts an actual load on your engine (like turning the a/c on would do) to better diagnose your actual problem's source.

As far as "prep" goes for the belts, if you say there is some oxidation or rust, just sand the pulley's to get surface crap off. Probably not a big deal if you don't though.

The fact that Mercedes puts the A/C belt and the p.s. belt before the alternator belt is just plain stupid though...its such a pain because I would think it would be obvious that the alternator would require much more attention than the others would...it should be on the outside. Its just annoying to have to take others off is what I mean. Ah well.

Good Luck,

- James
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1974 240d "Peace, Love and Empathy" - Kurt Cobain
1982 300sd "It all depends upon the Benz!" - Me

1983 300sd
1985 500sel

1992 300se

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  #29  
Old 12-28-2007, 07:26 PM
Emu Rancher
 
Join Date: Mar 2002
Location: Washington, DC
Posts: 664
Problems solved. New belts and battery are installed. The car started up incredibly strong, didn't have to crank. I checked out the ground wire and sure enough the insulation was gone in one spot that looked like it was in contact with the roof hinge. I have duct tape on it right now but I am ordering a replacement. The 1000mm alternator belts worked perfectly. With the right parts and tools this is a 2 hour job. Once I got the car started voltage measured 14.49V across the positive terminal and engine block. I'll write this up for people's future reference.
__________________
W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.
Reply With Quote
  #30  
Old 12-28-2007, 07:49 PM
toomany MBZ's Avatar
Registered User
 
Join Date: Nov 2006
Location: central Va
Posts: 7,820
Quote:
Originally Posted by adiaw83 View Post
Problems solved. New belts and battery are installed. The car started up incredibly strong, didn't have to crank. I checked out the ground wire and sure enough the insulation was gone in one spot that looked like it was in contact with the roof hinge. I have duct tape on it right now but I am ordering a replacement. The 1000mm alternator belts worked perfectly. With the right parts and tools this is a 2 hour job. Once I got the car started voltage measured 14.49V across the positive terminal and engine block. I'll write this up for people's future reference.
WooHoo!!

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