Loud explosion inside cabin Z4M

[RossBMWZseries]

So as I park my car, I hear a LOUD bang in the cabin, so loud that I flinched like little b&$%#. Seconds after, I get this burning smell. I turned the car off, checked inside the trunk and hood but see nothing. I’m trying to start my car but it won’t turn. Starter is the culprit as I’ve been having issues with it. Has anyone experienced this? Anything I should specifically check?

[yousefnjr]

I recall a few months ago seeing a thread here with a similar complaint, loud pop out of nowhere and no start. Can’t remember whose thread it was. I think it was some kind of designed explosive charge in the battery cable or something.

Found thread — http://www.zpost.com/forums/showthread.php?t=1390948

[3798j]

Gotta think it's something else than the starter. It's hard to imagine the starter energizing while the engine is running...unless you inadvertently turned the key to the start position.

[Kream]

Same thing happened to me 2 years ago. It was the battery safety terminal. I told my mechanic to solder them back together without the BST.

[StickMon]

^WHS.
Holy Crap!!! Now it's trying to blow you up!

[RossBMWZseries]

Thanks for the thread yoursef, I do remember reading it in the past. My starter needs replacement as it’s been confirmed a few times by different shops, however, I’ve been sitting here in a parking lot for 2 hours now with no luck, leading me to believe that this POP was the BST. If the BST did blow up, there’s no way I can start the car now and drive it home right?

[RossBMWZseries]

By the way, if the BST is gone, is the burning smell normal?

[kav]

Sounds like the battery safety terminal. Some sort of explosive device on the battery terminal that is supposed to setoff during an accident. I had to replace mine a few years back and they are not cheap

[RossBMWZseries]

Yea runs for $200..

Here are two pictures I just snapped. I noticed my negative battery post seems a little toast from the edge and I don’t recall it being like that. Also, the positive terminal doesn’t seem to be intact. Does anyone know where the left red wire hooks into? Should I try reconnecting this or do I call it a day until I get the BST replaced?

[RossBMWZseries]

Here are the pics

[RossBMWZseries]

Originally Posted by Kream

Same thing happened to me 2 years ago. It was the battery safety terminal. I told my mechanic to solder them back together without the BST.

What exactly is being soldered here? Is the BST not necessary for the car to start and run?

[StickMon]

Here's a map of the main power distribution:

[zurus]

Originally Posted by RossBMWZseries

So as I park my car, I hear a LOUD bang in the cabin, so loud that I flinched like little b&$%#. Seconds after, I get this burning smell. I turned the car off, checked inside the trunk and hood but see nothing. I’m trying to start my car but it won’t turn. Starter is the culprit as I’ve been having issues with it. Has anyone experienced this? Anything I should specifically check?

There is your problem

[StickMon]

^WHS.
I think the cable you have in your hand goes to the jump start terminal, and the one that looks like it's still connected goes to the fuse block.
I say looks connected because I would bet that it gets connected to the positive terminal through the bit that vaporized.

As to solder what together. Everything. Both cables and a battery connector.

When this eventually happens to me I'll probably cut all of the crap off the ends of the cables and splice them to something like this.

Did that to my Son's truck when his cables dissolved from corrosion.
Nice solid connectors. Takes some creativity, though, to get it put together.

[kav]

Oddly enough my blown BST presented as an airbag light. The car would start. It cost well over $500 with install in Canada at dealer.

[StickMon]

The BST is supposed to blow when the airbags deploy.
What makes them spontaneously ignite is a mystery that I think BMW should be looking into.
Once the igniter is blown open you get an airbag light, because the airbag module can't see the resistance of the igniter anymore.

There's a fix for that in one of the referenced threads.

[SaltyNC]

You might be interested in this. There are also junk yards if you can find a wrecked Z4.

[StickMon]

^That's the money shot!
Clever guy. You can also see how he connected the cables to the positive terminal.

Problem solved!

I should do this proactively.

[RossBMWZseries]

I just got home, left the car behind. Gonna have to pull the Z4 home later on once traffic dies down. I’ll call the dealer tomorrow morning to see if the BST is in stock. Bypassing the BST seems like it’s out of my comfort zone as a DIY, and I don’t know what shop I’d take it to.

[Punisher3.0si]

Originally Posted by 3798j

Gotta think it's something else than the starter. It's hard to imagine the starter energizing while the engine is running...unless you inadvertently turned the key to the start position.

Euro cars have a manual lock out preventing that from happening.

[dc_wright]

At least for the M you only have to buy the short intermediate cable (61127841239). For the post face lift non-M (didn't check for pre-facelift), you have to buy the full cable that runs from the battery all the way up to the convenience terminal, or you have to rig your own setup including the adapter to fool the SRS computer into thinking the bridge wire in the BST is still there. I was going to go that route but I checked with one of the tech inspectors for the local SCCA chapter and he indicated that I'd either need to have a factory supplied repair kit, a new cable, or a time trials compliant battery cutoff. I went the route of the new cable.

[The HACK]

Have you tried jump starting the car? Car should still run without the battery.