Alternator Bolt Issue - 85 300D cali - PeachParts Mercedes-Benz Forum

::matthew · #1 03-07-2010, 10:04 PM

I've been experiencing a rattling noise and I had determined that is was the alternator bracket. I tightened down all the bolts and although it improved, the sound did not go away.

Tonight I realized that there is an issue with the "pivot" bolt that connects the alternator to the bottom bracket. The alternator will move within the space between the bracket and it appears that the bolt is actually bent or broken. The bolt will not come out nor will it get super tight.

So, two questions:

1) looking at the EPC drawing, it seems to show the bolt coming from the front of the car, whereas mine is coming in from the back. Has mine been altered or is this perhaps a cali thing?

2) I'm planning on removing the bracket to deal with the bolt. Is there anything I need to look out for? Any common mis-steps that cause this to turn into a bigger project?

vstech · #2 03-07-2010, 10:25 PM

my bracket also is tightened from the rear. and I don't have a cali, so I'm sure it's the same.
the bolt threads into the nut welded to the front of the motor I think... I don't remember. get a good look front and back. (I bet that's hard with that cali air filter in the way!!!)
I bet you have a nut spinning.

::matthew · #3 03-07-2010, 10:32 PM

there's definitely a lot of things preventing a good view from the front. Good to know that my bolt wasn't a "custom" job...
So if the bolt isn't broken, but the nut is spinning, what is the best course of action to get it corrected?
I did look at the front from underneath while turning the bolt from the back and didn't see any movement, so a spun nut might not be the issue.

jt20 · #4 03-07-2010, 10:39 PM

my bolt goes through the back as well. The bracket is threaded to accept the bolt, since its aluminum, perhaps it is toast?

vstech · #5 03-07-2010, 11:29 PM

ooooh... that sucks... gotta replace or helicoil the bracket...
the older models have a steel bracket with a nut welded to it...

charmalu · #6 03-08-2010, 01:27 AM

That is bolt #158 in the above diag.? mine comes in from the rear also. that aluminium bracket is threaded, along with the alternator. the bolt which is steel, will rust along with the corrosion from the aluminium. it hangs down low and is subjected from all the road slush etc.... it will be in there so tight you would think it is welded in.

when I was trying to remove the alternator, the bolt would turn, but not unscrew to the point it would come out. I removed the whole bracket with alt. sat it up on end and soaked it with PB Blaster for 2 weeks. even used an impact wrench to it. finally used a smaller diameter bolt, and beat the snot out of it, finally she came out. now I slather it really well with anti-seiz compound.

Charlie

Cr from Texas · #7 03-08-2010, 02:24 AM

That bolt on mine broke and converted the round hole to oval in both the bracket and the alternator housing. Had to replace both. Found the parts at PNP and switched to the higher output alternator (that's all that was there). I think I suceeded in turning a - into a +.

::matthew · #8 03-08-2010, 08:35 AM

Thanks for the input guys. I'll head to the PnP prior to removing it so I have an extra bracket on hand.

snookwhaler · #9 03-08-2010, 08:45 AM

I removed my alternator last week. After removing the alternator, bolts and bracket from the car I found the bottom bolt to be worn almost all the way through.

From vibration I guess. It was difficult to remove the bolt because of the wear. I had to have a helper wiggle the alternator around as I gently pounded the bolt out. What a PITA!

Both of the gouges in the bolt were about half way through the bolt. I tried to order one from the site. But, it looks like it will be a "dealer part".

That sucks about the bracket Matthew. I know a good local welder that could repair it. If I remember correctly, it is just a nut welded to that bracket.

EDIT: Here is a pic of the worn lower bolt compared to the top.

http://i247.photobucket.com/albums/gg133/litespeed58/Loweralternatorbolttoast.jpg

::matthew · #10 03-10-2010, 12:15 AM

Issue was dealt with tonight.

bolt was broken and was stuck in the cast lower bracket that is attached to the block. Why MB thought that 4 studs on the side plus one in the front was required to keep that thing on is beyond me. I couldn't get the front bolt out and had to deal with the bracket in place, on the car.

Even with a right angle drill, it was too tight quarters to get an easy out in there. I ended up grinding the "nut" part of the bracket off along with the broken part of the bolt. I used a 5" 3/8" bolt in it's place along with a lock washer and nut. The 5" bolt was slightly short, so I used the grinder to create a bit of a shoulder on the rear end of the bracket.
Not the way I would have liked to have done it, but I needed to get the car back on the road.
The hole going through the alternator is "wallered" out and is way out of round. This causes the looseness and is probably the cause of the bolt failure.

I replaced the voltage regulator while I had the alternator out.

vstech · #11 03-10-2010, 08:54 AM

ya might wanna bite the bullet and get a replacement alt in there. that 3/8" bolt isn't gonna hold up with a wallered out alt, and a ground face to sit on...

snookwhaler · #12 03-10-2010, 09:19 AM

Quote:

Originally Posted by ::matthew

Issue was dealt with tonight.

bolt was broken and was stuck in the cast lower bracket that is attached to the block. Why MB thought that 4 studs on the side plus one in the front was required to keep that thing on is beyond me. I couldn't get the front bolt out and had to deal with the bracket in place, on the car.

Even with a right angle drill, it was too tight quarters to get an easy out in there. I ended up grinding the "nut" part of the bracket off along with the broken part of the bolt. I used a 5" 3/8" bolt in it's place along with a lock washer and nut. The 5" bolt was slightly short, so I used the grinder to create a bit of a shoulder on the rear end of the bracket.
Not the way I would have liked to have done it, but I needed to get the car back on the road.
The hole going through the alternator is "wallered" out and is way out of round. This causes the looseness and is probably the cause of the bolt failure.

I replaced the voltage regulator while I had the alternator out.

Matthew, did you see that picture I put up in the above post? It is a "link" to a picture.

My lower bolt was worn almost all the way through and was slightly bent. It was a serious PITA to get out of the alternator. Not much room to do anything down there with a hammer. I had to pound it out at an angle with a long steel bar. Above is even worse. I'm assuming you had to remove the fan and shroud to grind that nut off? What a PITA!

My alternator lower hole was all "wallered" out too. But, I found that getting that lower bolt really tight stops any movement. I think it was just too loose before and the wear is the cause of it being "too loose".

I did the regulator too. It was completely toast:

http://i247.photobucket.com/albums/gg133/litespeed58/Voltageregulatorbeforeandafter.jpg

::matthew · #13 03-10-2010, 04:16 PM

Quote:

Originally Posted by snookwhaler

Matthew, did you see that picture I put up in the above post? It is a "link" to a picture.

My lower bolt was worn almost all the way through and was slightly bent. It was a serious PITA to get out of the alternator. Not much room to do anything down there with a hammer. I had to pound it out at an angle with a long steel bar. Above is even worse. I'm assuming you had to remove the fan and shroud to grind that nut off? What a PITA!

My alternator lower hole was all "wallered" out too. But, I found that getting that lower bolt really tight stops any movement. I think it was just too loose before and the wear is the cause of it being "too loose".

I did the regulator too. It was completely toast:

http://i247.photobucket.com/albums/gg133/litespeed58/Voltageregulatorbeforeandafter.jpg

the majority of the bolt came out. looked just like yours. The last bit was removed when I ground the threaded part off the bracket. As far as tightening the bracket to deal with the "wallered" alternator hole, just be sure to not tighten it too much. I noticed a hairline crack in mine.

I'll be going back with some JB weld. While I'm down there, I'm planning on taking the lower bolt back out and using a washer on either side of the alternator in the bracket to take up the extra space.

The bolt I used was a Grade 8, so I'm not too worried about it failing any time soon.

Maki · #14 03-11-2010, 02:29 AM

I had the same thing happen. Galvanic corrosion can be a bear. I took the bracket off the car and brought it to an auto parts store with a machine shop (Bumper to Bumper). They Helicoiled it for the proper bolt. Like new again for maybe $25.