Please critique this underbody

[twistinglane]

Mechanicals are newly rebuilt. But why was put together without taking care of underbody is a long story I gather.

Edited October 26, 2017 by twistinglane

[yeewiz]

52 minutes ago, mike said:

That hole is actually a drain hole...like belly buttons on people, every 02 has one (actually two, one per side).  They're the drains for the frame rails' nether ends.  

 

thanks Mike, apologies to all, I thought I was looking at the front of the frame rail.  You would think after owning this thing for 43 years I could tell which end was which

Edited October 26, 2017 by yeewiz

[Conserv]

It's a '74 and, like other square taillight cars, it has a box section at the right rear corner, under the trunk floor, between the fuel tank and the rocker panel.  The photo is slightly ambiguous in this area, but this box section is an amazingly rust-prone component and the bottom of the box section appears to be rusted away completely.  Even my very low rust '76 had this component rusting through by...maybe 1980!  Below are some photos of what my '76 looked like by the time of it's recent/current re-paint.

 

Maybe it’s a trick of the photo, but I believe the boxed section has no bottom.  There are a few threads that discuss this particular area.

 

Other than that area — which warrants a close-up examination or more photos — it’s a pretty darned clean underside!

 

Regards,

 

Steve

 

 

Edited October 27, 2017 by Conserv

[Hodgepodge]

I think maybe you asked the wrong question.   If you ask for a critique, you will get all sorts of comments about the individual areas under the car and a lot of suggestions about things that might be wrong.     You will ALWAYS have some issues under a 40 year old car.    If you ask for a rating of the visual condition of this car on a scale of 1 to 10 where 10 is the best.  I would probably rate the underside of this car an 8+.  Why?  There is virtually no rust other than minor, easily resolvable surface rust and a few spots near the gas tank and potentially in the spare tire well.  There are no patches that I can see, there is no sign of collision damage.  The drive train, including the entire rear-end has been removed from the car and completely rebuilt.  The CV joints, drive shafts, engine transmission and differential don't even look like they have been wet since the rebuild. 

 

Why not a 9?   Well, there is some surface rust and there is no way for ME to tell if the car was just pressure washed or if it was done a while ago.  If it was just done, there could be a fluid leak or two that can't be seen.  Also, LikeStig noticed the gas tank support section at the bottom of the rear quarter panel, which looks to me like it has been cut out to resolve some rust.  This is an incredibly common rust area in all BMWs and should be addressed by welding that little box beam back together.  (My car has exactly the same issue.)    Remove the tank and check the tank seat lip for any rust there.   

 

Oh, there is some tape on the bottom of the spare tire well.  The only reason I can think of for that tape is to cover some rust holes from water settling in the spare tire well.   Pull the spare out and look closely.  Pull the tape off if you can to see what is under it and check the trunk gasket VERY carefully to make sure there are no current leaks.  A new gasket is a lot cheaper than rust repair.  

 

If you wanted a critique to see if you should buy the car.  The answer is not just yes but hell yes. Buy it.  If this is your car and you wanted a critique to see what we thought of the job you did cleaning it up and dealing with the drive train, it looks fantastic!   Whoever the owner is, he/she should be proud!   

 

Thanks,

 

Scott

 

[ray_]

I concur.

 

But, look closely at the rockers.

 

By look, I mean with a screwdriver and a hammer.

 

 

Also if the heater box seal leaked, you wil have hidden firewall/floor rust issues. AMHIK

[TobyB]

Since you asked, whassis?

 

Hard to see exactly, but it's bent, and the rear

lip of the wheelarch can rust.

 

Overall, looks pretty good for corrosion-

and like it'll be a real project to seal up properly.

 

t

 

Edited October 27, 2017 by TobyB
oops. needs moar pic.

[Conserv]

10 hours ago, TobyB said:

Since you asked, whassis?

 

Hard to see exactly, but it's bent, and the rear

lip of the wheelarch can rust.

 

Overall, looks pretty good for corrosion-

and like it'll be a real project to seal up properly.

 

t

 

 

Toby,

 

This was my point above as well, and the reason I showed photographs of the same box section on my ‘76.  But I’m not “equipped” to make these nifty red boxes, so I’m guessing my point went off into the ether!  It looks to me as if the entire bottom of this box section is gone — as in rusted away — but maybe that’s a trick of the photograph!

 

As I said above, that box section on my ‘76 had a rust-through hole by ca. 1980 — on an otherwise rust-free car!  It’s not an important piece: it was simply a stiffener required to comply with higher crash standards.

 

Best regards,

 

Steve

Edited October 27, 2017 by Conserv

[TobyB]

Sorry, Steve, I thought the box section you were talking about was the center spine that got added, not the fender whooahh.  I have cut apart a couple of squaries,

and I don't remember them being much different, at the sides, aside from the stiffener glued into the fender panel.  But it's been a while.

 

And the 'whassis' was for the bending- it's either weird looking in the pic, or it's bent somehow.  Or just rusty, I guess, now looking...

 

t

 

[Simeon]

Having recently refinished the structure around the wheel well and fuel tank on mine, the obvious areas of trouble are the narrow areas against the rear valance. Not convinced they got great coverage when painted in the factory and obviously have the seam of the trunk floor to start rusting. This is before the box sections that BMW added. 

[mbausa2001]

How about the small “hammer” test! Tap all undercarriage areas to assess the weak inside out rust areas?