Battery replacement coming tomorrow. Any suggestions on the broken bolt to come?

[Cremaster]

I have the simplest of jobs tomorrow. Replace the battery on the Z. Remove the cables, remove the long hold down bolt on the battery, remove battery, replace battery........................

So I looked at the job this evening and the battery hold down bolt has corroded. The shaft of the bolt has eroded and the threads seem to be acid welded. I tried to bump the bolt both ways but it is in pretty tight. I did spray it with one of those rust buster sprays before I came in for the evening.

In the morning the bolt will break off when I turn it. Anyone know where to go from there, a undetermined length of broken and corroded welded bolt and threads that there is no way to reach with any tool that can do anything.

[BimmerBreaker]

Your local auto parts store will sell battery post clamps to replace your existing ones

[Cremaster]

I am not concerned with that post. The threads are on the bottom of the post and tightens on the bottom clamp.

[z3forlife]

Maybe try some heat from below prior to loosening ? Of course after the penetrant evaporates. If it breaks then soak it in oil or just drill it out slightly smaller than the bolt and you could run a tap through to clean or enlarge if the nuts not replaceable

[Randy Forbes]

I think he's talking about the bolt that secures the battery to the floor...



If it breaks, it breaks! Faced with a job like that, I reach for my LEFT HAND drill bits__and a reversible drill, obviously__and go after removing the stub that way. Left hand drill bits are far more successful at removing broken bolt stubs than any type of easy-out (Vice-Grips may be an exception, provided that there's enough of the stub left to grab?).

[Vintage42]

... the battery hold down bolt has corroded... the bolt will break off when I turn it. Anyone know where to go from there, a undetermined length of broken and corroded welded bolt and threads that there is no way to reach with any tool that can do anything.

Are you sure that you can't keep patiently using spray and heat to eventually get the screw loose without breaking off the threaded end? New parts would be:

61217577620 -- 190mm mounting screw
https://www.ecstuning.com/b-genuine-bmw-parts/mounting-screw/61217577620/

A8 Washer

461217566618 -- Battery Hold Down
https://www.ecstuning.com/b-genuine-mini-parts/battery-hold-down/61217566618~oem/

54318246804 -- M6 Circlip
https://www.ecstuning.com/b-genuine-bmw-parts/circlip-priced-each/54318246804/

If the old and new batteries do not have a vent tube, one can be bought from AutoZone or Amazon:
https://www.autozone.com/batteries-starting-and-charging/battery-vent-tube/dorman-battery-vent-tube/268946_0_0

[rf900rkw]

Heat and batteries do not mix.

[Vintage42]

I forgot about no working room for a heat gun or pencil flame with the old battery in. Maybe a soldering iron will poke down there.

[z3forlife]

Is it accessible from beneath

[Blacklane]

My non-M Roadster has a pretty deep battery well and my hold-down bolts were missing when I got it, so I just inserted a couple of boards (including a 2x4) into the spaces around the battery. That really holds it securely.

[melville]

My non-M Roadster has a pretty deep battery well and my hold-down bolts were missing when I got it, so I just inserted a couple of boards (including a 2x4) into the spaces around the battery. That really holds it securely.

It's a BMW, not a VW Bus! Go spend a couple bucks and get the right hardware.







Full disclosure--I'm a longtime ACVW owner, and the main challenge with an old VW is fixing the PO bodges.

[Cremaster]

The bolt broke in the perfect place allowing the hold down clamp to release and I got the battery out with no problems.

Then the real problems showed. The area that the battery sits in is all corroded and compromised. The little depression looks like Bmw designed it to hold battery acid and eat through the floor of the trunk. The rest of the bottom is crap as well. Where the round part is it has allowed fluid to drip out on to my floor. No biggie but I wonder what else it ate away at to get to the floor.

The picture is not as bad as it was. I cleaned it out a bit. I put baking soda in there and let it fizz for a couple of hours, wiped it all out and did it again and I will leave it over night.

Now the big questions. How to repair this mess. The clamp part nearest to the lip of the trunk has threaded areas and a raised area that the acid can hide in. It looks like I might have to cut it out and weld in a new bottom which I do not have the tools for.battery1.jpg

Anyone have any suggestions on where to go now. Pic attached.battery2.jpg

[jrkoupe]

cremaster?




really.......thats a crazy name to use?

any significance?

[Vintage42]

... The area that the battery sits in is all corroded and compromised. The little depression looks like Bmw designed it to hold battery acid and eat through the floor of the trunk... I put baking soda in there and let it fizz for a couple of hours, wiped it all out and did it again and I will leave it over night. Now the big questions. How to repair this mess....

There should have been no acid in the well unless the vent tube in the photo was disconnected.
You should be able to remove the bottom rubber drain plug and get the well clean enough to treat rust and repaint it.
If you can get the broken bolt out, and the threads in the well are still good, new hold down parts should work. Otherwise there's the wood blocking method.

[Cremaster]

So the round part is just a rubber piece of the drain? Yahoo!!! I will drill new holes for a new battery hold down, it may not be concourse acceptable but it will be good enough for me. The wood thing would drive me nuts if I had to do that.

There was a vent tube but I think the battery vent was defective. The battery looks like it has been very hot and I may have done it with to many amps to get the dead battery to take a charge.

[Cremaster]

cremaster?




really.......thats a crazy name to use?

any significance?

No actual significance really. I took anatomy when windows 95 and all the message boards came out, and I wanted a unique name that was easy to remember, would not be taken by others, but at the same time easy to remember. So in class I learned what it was and also that there was a reflex named after it. I have only signed up to one forum that said the name was taken and I suspect that it was a forum I signed up to earlier.

So none of that "BMW905732vv274" stuff for me, even though I suspect that it is available for most message boards out there on the internets, So did you notice it because you know what it is or because of some other reason? Have a good evening sir.

[Vintage42]

... So in class I learned what it was and also that there was a reflex named after it...

What a sleeper of a name. So that's where "suck it up" comes from. Who knew.

[Adker]

There was a vent tube but I think the battery vent was defective. The battery looks like it has been very hot and I may have done it with to many amps to get the dead battery to take a charge.

You can also put in a acid neutralizing mat, cheap insurance.
https://www.batterymart.com/p-batter...CABEgIBvfD_BwE

[neopolymath]

No actual significance really. I took anatomy when windows 95 and all the message boards came out, and I wanted a unique name that was easy to remember, would not be taken by others, but at the same time easy to remember. So in class I learned what it was and also that there was a reflex named after it. I have only signed up to one forum that said the name was taken and I suspect that it was a forum I signed up to earlier.

So none of that "BMW905732vv274" stuff for me, even though I suspect that it is available for most message boards out there on the internets, So did you notice it because you know what it is or because of some other reason? Have a good evening sir.

I figured we had to have someone with anatomical knowledge to choose that name. Sometimes I use it as a trivia name...

[jrkoupe]

Im in the health field......


its a funny name to choose.

most would have no idea of its meaning or etiology..