[PassiveDefect]

new to the forum, tried searching but I have no idea what these are so dunno how to even go about searching for them.

got a 2008 335i, had the car on a lift and saw corrosion on what seems to be the outside of the battery tray.

[Welcome to NBA Jam]

The small one looks like the battery vent tube, the other ones I have no idea. One of them looks like a big red positive cable, so the other must be negative.

Clean the area and see if it's just mud/gunk and not rust. If it's rust, you'll want to take care of it now while it's minor.

[OTO335i]

Originally Posted by Welcome to NBA Jam

The small one looks like the battery vent tube, the other ones I have no idea. One of them looks like a big red positive cable, so the other must be negative.

Clean the area and see if it's just mud/gunk and not rust. If it's rust, you'll want to take care of it now while it's minor.

That's correct, The small tube is the vent and the two others are power and negative cables. The negative cable seems to have some corrosion at the grommet. I would clean the area and keep and eye on it.

[PassiveDefect]

Originally Posted by OTO335i

That's correct, The small tube is the vent and the two others are power and negative cables. The negative cable seems to have some corrosion at the grommet. I would clean the area and keep and eye on it.

it seems like the corrosion cracked the housing. if you zoom in you can see wires. gonna take a trip to the dealer and see if I can buy this separately

[Cabdriver]

You caught this at a good time, highly recommend cleaning up this area, sand, respray. It would not at all be difficult but do some research and prep on how to get that rust out.
Its becoming more than surface but still treatable.

[gbalthrop]

Originally Posted by PassiveDefect

new to the forum, tried searching but I have no idea what these are so dunno how to even go about searching for them. Got a 2008 335i, had the car on a lift and saw corrosion on what seems to be the outside of the battery tray.

BOTH of the cables are 12V+ or B+ battery supply lines that run to the engine compartment and BOTH should have RED insulation. The larger gauge wire is connected to the Starter & Alternator, as well as the Jumpstart Terminal. The smaller gauge wire goes to the E-box and provides power to the DME, etc.

Here is a TIS procedure for changing one of the two cables that shows BOTH from the battery compartment (inside) and explains function:
https://www.newtis.info/tisv2/a/en/e...ble/1VnXWUgICS

The corrosion/rust shown in your photos suggests that either you have/have had water in the battery well, or worse yet, a defective voltage regulator causing more than 15.0V alternator output, boiling battery acid that is VERY corrosive. In either event, I would suggest:
1) checking system voltage with engine running to make sure <15.0V;
2) removing the battery cover, removing the battery, and properly removing/treating any rust/ corrosion present on the inside of the well;
3) With battery removed, disassemble & clean the transfer point connections & insulators, as well as treating the rust around the "passthrough" holes in the chassis.

BTW, you appear to have a "NOW-small" hole in your R muffler at the hanger-rod weld, and corrosive exhaust on that area can't help. High-temp epoxy can buy you some additional muffler life.

George

[PassiveDefect]

Originally Posted by gbalthrop

BOTH of the cables are 12V+ or B+ battery supply lines that run to the engine compartment and BOTH should have RED insulation. The larger gauge wire is connected to the Starter & Alternator, as well as the Jumpstart Terminal. The smaller gauge wire goes to the E-box and provides power to the DME, etc.

Here is a TIS procedure for changing one of the two cables that shows BOTH from the battery compartment (inside) and explains function:
https://www.newtis.info/tisv2/a/en/e...ble/1VnXWUgICS

The corrosion/rust shown in your photos suggests that either you have/have had water in the battery well, or worse yet, a defective voltage regulator causing more than 15.0V alternator output, boiling battery acid that is VERY corrosive. In either event, I would suggest:
1) checking system voltage with engine running to make sure <15.0V;
2) removing the battery cover, removing the battery, and properly removing/treating any rust/ corrosion present on the inside of the well;
3) With battery removed, disassemble & clean the transfer point connections & insulators, as well as treating the rust around the "passthrough" holes in the chassis.

BTW, you appear to have a "NOW-small" hole in your R muffler at the hanger-rod weld, and corrosive exhaust on that area can't help. High-temp epoxy can buy you some additional muffler life.

George

thank you! man you guys are awesome, gonna take it to a body shop Saturday. not really good with paint/prep.

the car sat for 3 years with a stone dead aftermarket battery on grass so both I guess :

battery been replaced with an OEM one for few months now. gonna take it out and examine the rust from the inside
will update with repairs