Sanity check on jack point and brake line repair approach

[megatron]

Hi guys,

Just wanted to think out loud on this and get your thoughts to make sure I'm going about this optimally. I'm preparing a M42 318i sedan for inspection, and found a few things.

1) The right rear body jack point is not only collapsed, but it looks like there is rot around it, likely starting from where it collapsed.
2) The fuel tank is also dented up at the bottom near that spot, probably related.
3) The brake lines, particularly the main hardline from front to back, are rusted.

I want to do this properly, meaning dropping the subframe. Problem however, is the subframe cross member is the jack point if not using the body jack point.

So I'm thinking to do this:

1) Hold car up by cross member in the right rear
2) Drain and remove fuel tank
3) Cut and weld in replacement right rear jack point and surrounding metal
4) Move jackstand to the replaced rear jack point
5) Drop subframe
6) Replace brake lines
7) Opportunistically replace fuel lines
8) Opportunistically replace bushings while subframe is on the the ground/bench
9) Reassemble

Does this sound like a sound approach? Is there a faster way I haven't considered?

I'll probably end up rerouting the lines to 318ti style routing when replacing them.

Thanks!

[jlevie]

Sounds reasonable to me.

[redlightpete]

I haven't used the factory jack points for fear of the damage you're describing. In the back I've put jack stands on the 'frame rails' behind the rear spring perches. It is a tight fit on the exhaust side, and you need some tall jack stands. I used some pieces of wood between the car and the jack stands to avoid damaging the underbody coating.

[Coupenut]

I'm just about finished replacing the hard brake line from the front of my 88 iX, as well as all of the rear lines and other components. I was able to accomplish this without removing the rear sub-frame.
One suggestion however, it is very difficult to remove the hard line from the proportioning valve at the front of the car. There's very little space or visibility. There's a writeup here and on Bimmerforums about this particular task and the author (barbierij) talks about difficult it was to remove the hard line from the proportioning valve.
Rather than deal with this issue, when I replaced the line on my car I removed the master cylinder and booster, not a difficult task, now you'll have plenty of space to work and the valve is easy to see.

[megatron]

Sounds reasonable to me.

Thanks!

In the back I've put jack stands on the 'frame rails' behind the rear spring perches.

Didn't realize that was a option. Are those points "officially" deemed OK as jack stand points?

Rather than deal with this issue, when I replaced the line on my car I removed the master cylinder and booster, not a difficult task, now you'll have plenty of space to work and the valve is easy to see.

Great tip, will do this, thank you!

[jlevie]

Thanks!
Didn't realize that was a option. Are those points "officially" deemed OK as jack stand points?

Dunno if those points are "officially" blessed, but a lot of weight is going to come off the rear when you drop the subframe, diff, etc. So I'd think they'd be okay.