Not a happy discovery- rusted floor pan

[VWScott]

Well today I got all the carpet removed and yes this is what I discovered. Well its only half shown here. Driver side is the same. So... I've done floor pan quarters on many VWs but since this is my first BMW I have questions. 1. I know there is a rail that runs down the middle or so underneath the front floor pan. What is the way to cut out this whole area then? How do you separate the two? 2. I can only assume that once separated this rail will probably be toast or Swiss cheese and beyond repair.Are they available?

I will probably take this opportunity to replace the fuel line even though it has no issues but still it is almost 50 years old. I havent looked real closely but it appears that the floor pan half wont cover the extent of the rust or barely reach good metal at the front. I'm curious what folks do if that underneath rail is trashed? especially if there is not a replacement piece available. It seems a difficult item to make from scratch if needed. Ideas???

Driver side has additional landmines of return fuel line and brakeline underneath yes?

[tech71]

The frame rails are critical, integral structure, they basically

support the subframe, engine and drivetrain.

1 hour ago, VWScott said:

What is the way to cut out this whole area then? How do you separate the two?

Cut the rotten floor panel out around the rails, dont cut the rails yet!

The rail is attached to the floor panel with spot welds, normally you separate them by carefully drilling out the spot welds.

1 hour ago, VWScott said:

Are they available?

Yes, available from W&N, MVP and a few others.

A couple of members are currently or have recently completed floor pan replacements, check it out, hit them up😉

 

Edited January 19 by tech71

[tech71]

1 hour ago, VWScott said:

I havent looked real closely but it appears that the floor pan half wont cover the extent of the rust or barely reach good metal at the front.

All that vertical metal is not part of the replacement floor pan, I dont believe there is a repair panel for that. a decent piece of metal must be obtained from a donor car or it has to be fabbed up.

 

1 hour ago, VWScott said:

I'm curious what folks do if that underneath rail is trashed? especially if there is not a replacement piece available. It seems a difficult item to make from scratch if needed. Ideas???

Repair is possible in some instances by welding on doublers, patches ect but if its too far gone it must be replaced.

Have to pull engine/drop subframe to replace them.

Corrosion looks pretty heavy but I dont see any holes...

What ever you do, its time to correct whatever problem is allowing moisture to get up in there... probably a blown out heater core or a leaking front glass seal.

Edited January 19 by tech71

[tech71]

58 minutes ago, VWScott said:

Driver side has additional landmines of return fuel line and brakeline underneath yes?

Your 76 was built with a fuel return line routed along the rocker panels, think brake lines are located running thru the tunnel.

[VWScott]

I only took a quick glance under there this afternoon. Two lines running underneath along the rock on underside driver floor pan. One bigger than the other. I just assumed one fuel return and the other brake line.Will investigate further when I get to that part.

[tech71]

Actually, That may be the brake line, might have been thinking of my 71..My bad.

I would get it all cleaned up before doing any cutting

Edited January 19 by tech71

[JsnPpp]

I didn't know MVP also made frame rails, thats awesome. I don't have anything else to add that hasn't been said 🙂 

 

Jason

[VWScott]

There is evidence that heater core was leaking at some point. It must have been repaired because it is not currently so damage has been done. Seals? they are my list for the Spring repairs. I only purchased this car in November so I am discovering as I go.

[tech71]

Heres another possible source of repair panels

 

BMW Parts: Restoration Design Inc.

WWW.RESTORATION-DESIGN.COM

 

[VWScott]

Yes let's cross our fingers that rail is in adequate shape or at least fixable

[lunarkingdom]

You will want the MVP panels, that link to the floorpan restoration on my 1974 was mine and the MVP flor pans have an extra 1.5-2 inches in the front and on the tunnel sides which came in very handy as the front and the tunnel was rotten about the same so once I cut out all the rust and sand blasted it I was able to attach the MVP pans in very nicely.

Look out for not only the brakes lines in the tunnel but also the clutch master and slave hose that goes between them, right under the tunnel where your gas pedal is. check out the thread of mine it shows almost everything. Good luck!

[Son of Marty]

The 75 and 76 years in the US had the brake lines moved to the left frame rail to keep it away from the heat of the thermo-reactor exhaust.

[VWScott]

98hp won't cook bacon let alone thermo-reactor😉thks SOM!

[VWScott]

Thks lunarkingdom! I just checked out your thread.Way helpful.I was curious how to attach rail to pan or mor to the point how to know where the rail was once the pan was in.Drilling through from below!!!! Anyway I bought the pan halves this morning from Koogle

[TobyB]

I try not to be little miss doomandgloom on here-

 

but I've seen rust, and I've seen RUST, and what you gots there is R U S T.

 

With a capital RUST.

 

Now, if someone dumped 5 lbs of rock salt into the footwells by accident in 1984*, 

then you might be OK, but what I see there is a lot of salt- accelerated rust.

So before you buy anything, it's time to really start taking the rest of the car apart,

and attack all the usual rust spots with malice.

Because if the floorboards look that bad, the rockers, rear subframe mount structures,

spring perches and so forth may be that bad, or worse.  And when you add all that rust

repair, different shells beckon.  Because there are still lots of shells out there.  

 

As to the specifics,

Quote

The frame rails are critical, integral structure, they basically

support the subframe, engine and drivetrain.

isn't quite correct.  The 2002 has no frame rails- what you see under the floor is the trailing end of

the bottoms of the front fender structure, which DOES support the subframe.  The trailing boxes that

go into the floor are just for a bit more stability, and control of structure deformation in a crash- basically, they

pull the floor down, so that it doesn't buckle UP and into your feet, and so that the engine and trans will be directed down

under the shell as it crumples.

Had they been for strength, they would have been tied into the sills, and they intentionally avoid that.

The 'inner front fender' is carrying the weight of the car, and attaches to the sills and the a- pillar

(oh, yeah, these structures can rust like hell too, so go at THEM with a pointy hammer, too)

which provide the 'structure' of the shell.  It's pretty soft, partly by intent- it sacrifices itself to reduce peak G's on the 

people inside.

The bottom of the inner front fender's tied into the sills via some pretty heavy sheet metal in one plane,

and then boxed to prevent it moving laterally when it's vertically loaded with the weight of the passenger 

compartment. The 'firewall' structure maintains the relationship between the inner fenders, more or less,

as does the front subframe.

Then there's some triangulation to add stiffness to that front 'fender-firewall-fender' plane, and also to help

transfer the weight of the shell onto the front upper spring perches.

It's pretty neat.  And very intentional.

 

And a sumbitch to fix when it's all rotten out.

 

t

*I own a 1965 Volvo 122 'Amazon'- the driver's floorboard looked almost that bad,

because the heater core leaked into the floor material, and the floor material became

very acidic when combined with the coolant.  The rest of the (Florida) car had almost

no rust anywhere.  So if that's your case, ignore me and replace the floorboards, and motor happily.