Went to start the beater of a truck and the starter turned slowly for a second then nothing. Had this happen last year and tightened the cables at the battery and it was fine. I went to clean up the positve cable at the battery and that went fine...re-attached to the battery and tried it and nothing. I figured to clean up the negative terminal and just as I cracked the nut loose the battery started to smoke out the front...so I ran away. I waited for the smoke to stop and undid the neg. cable at the steel alternator bracket end cause I did not want to be close to the battery. I went to undo it from the battery end and the nut was really hot. I am getting sparks from the neg. terminal nut every time I try to loosen the bolt. I am not sure how there could be sparks coming fom that nut as the positive cable and the negative cable from the alternator bracket end is disconnected......essentially the nut on the neg. terminal at the battery is sparking while the battery is disconnected. I am sure this would rule out a short in the trucks electrical system......so is the battery shorted out inside? Should I be worried about the battery exploding?

If you love your face man, ruuuuunnnnnnnnnnnnnn.

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I would consider that battery a total loss. Get it to a recycle center ASAP, no need to risk your health/safety on a questionable part that can be replaced fairly easily.

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2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)

Sounds like the starter is still engaged. I agree that battery is finished

X2 on that one.

I drove my beater chevy truck to the 7-11 one evening...everything was fine... when I came back out to go home.. BAAAAAAMMMMMM
Covered the whole inside of the hood with acid..
avoid that battery like the plague...

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Is there advice for the OP to somehow disconnect a sparking battery? He's said the positive post is disconnected and the other end of the negative cable is disconnected. So it's arcing from where to where?

It sounds like there's another path to ground from the negative cable and the battery is shorted internally. Any other guesses?

Assuming the bad worst case of hydrogen fumes and sparks, I'd say having a fire extinguisher handy is a must-have. Facemask, gloves, long sleeves, etc.

Thanks. Got brave and removed the old battery. Put a new battery in and as soon as I touched the positive wire to the terminal the starter engaged. So you were right. Funny thing is, the keys were in my pocket. Scared the !@#! out of me and all my tools...nuts bolts fell in the tall grass when I jumped backwards. I was already on edge from the smoking battery I guess. All is well now... thanks again.

That's what I could not understand either...how can a battery that is not connected to anything produce sparks from the negative terminal?

So I open the top of the cells today and found one cell to be almost totally dry and all rusty and corroded looking inside. All the other cells looked fine. Since you guys are all confirming this is probably not safe I will go take it out of the garage. I don't want to burn it down....or have an exploding battery. Judging from the smoke or gas or whatever was coming out of it I don't think it is worth messing with at all. Y ah when I ran away I got the hose too. Just a junky old chevy but its my dump truck.

I'll bet if you put a socket on that engine and roll it over the starter will disengage. Probably need to replace though.