300SD Alternator Removal Problem - PeachParts Mercedes-Benz Forum

razookelly · #1 01-31-2011, 06:36 PM

Hello All... I'm trying to take the alternator out of my 1984 300SD and I'm having trouble with the bottom bolt. I've found plenty online about people having trouble with the top bolt because of the tensioner, which I had no problem with. I've unscrewed the bottom bolt until it doesn't seem to come out any further, yet it's still difficult to turn and won't slide out. I'm sure I'm past the threads. The alternator wiggles and is lose. Has anyone else had problems getting this bolt out?

toomany MBZ · #2 01-31-2011, 08:33 PM

Is this bolt closer to the right side of the car (bolt #2), or engine block (bolt #3)?

razookelly · #3 01-31-2011, 09:01 PM

Hi. Thanks for the help. It's the #2 bolt - the bottom point that the alternator pivots on. I unscrewed it about 3/4", until turning the bolt no longer made the bolt move out. It still turns, but doesn't make any more progress. The bolt has been really hard to unscrew and is only slightly easier to turn now. Thanks again.

vstech · #4 01-31-2011, 09:04 PM

to make it easy, remove the third bolt on the bracket where it attaches to the mount near the block. upper side of the alternator rear close to the engine block.
remove that bolt, and the bottom bolt on the back of the alternator as far from the engine block as you can get. the alternator will drop right out, with the adjuster bracket and bolt still attached.

razookelly · #5 01-31-2011, 09:17 PM

Hi and thanks for the advice.

After getting the top bolt (that screws into the tensioner) out, the whole alternator swung down - pivoting on the bolt that I'm having trouble with. When it did, it exposed the nuts that hold the bracket to the block. It sounds like you're talking about removing those nuts and removing the bracket, with the alternator still attached. I took the 3 nuts that I saw off, but stopped there because it looked like the bracket extended further back and connected to a heat shield and maybe more. Is that not the case?

Thanks again

toomany MBZ · #6 02-01-2011, 09:05 AM

I had to take that bracket off, as bolt #3 would not come all the way out.

Bolt #2 threads into that bracket, see arrow. If that bolt (#2) is stripped, you're going to have to get it out of the car to repair it, I would think.

vstech · #7 02-01-2011, 09:34 AM

the NUT on the bracket at the block, is welded to the bracket, or it's supposed to be. I've seen several that were broken. but if you remove the bolt, yes the heat shield is in the way sometimes... but if you take out the lower bolt, and the bracket bolt, the bracket stays attached to the alt, and you don't have to mess with the adjuster bolt contortions getting the alt out.

LNGfish · #8 02-01-2011, 05:37 PM

1982 300SD Alternator Pivot Bolt won't unscrew!

This is a thread I started when I had the same problem. I'd take car to a muffler shop and see if they can get some heat on it and get it loose for you like I did unsucessfully.

The guy I used got some heat on it but I still had to soak it in penetrating oil since he gave up on it. I soaked it 3 days after he was unable to get it out but he did get it to turn 3Turns CCW.

I read the other responses here also. They may work also.

I can tell you that I far exceeded the force I figured would break the bolt but it finally came out. You may see it is cross threaded like mine was but I was able to reuse with some anti-seeze put on it. I used a 8" box wrench with a 2 foot cheater.

Get some really good rust buster. I use the stuff sold in CarQuest. Let us know how U make out. I know it is very frustrating.

razookelly · #9 02-02-2011, 02:19 PM

SUCCESS!!!!!!

I bought a pneumatic palm nailer (I had been looking at them and the battery ones for a while, but didn't think they would be useful - WRONG) and put a metal dowel in the threaded hole of the bracket. With this setup and progressively longer dowels, I was able to knock the bolt through. I love solutions where I get a new tool as part of the deal.

Before I reuse the bolt, I'm going to use my Dremel to grind the bolt and clean it up, so it will slide back in without binding.

Thank you to everyone who replied to my post. I hope I can return the favor someday.- David