Sill welding advice - The Unofficial BMW M5 Messageboard (m5board.com)

IvanDias · 9th July 2008, 16:17

Hi,

I had some welding work done to the front drivers (RHD) side sill done last year to go through the MOT.

The car has been developing a leak into the drivers footwell. Once I drained that I checked the windscreen seal, looks ok. I guessed sunroof drain and duct-taped the sunroof closed which immediately stopped water ingress.

Removing the carpet in the drivers side footwell shows a nasty spilt in the inner metal of the footwell and cill. To my mind it looks like the welders made busy with the external damage and left the internal split open.

The metal looks to be very thin here. I admit I cannot weld and have never seen it done so I have no idea what they do in these cases. What is of concern to me is that simply welding a plate over the hole will further compromise the thin metal in the area and the repair will corrode from behind so the issue will come back.

Would this be the logical way forwards, to let them do this if they want, or would I be better off locating and either extending or re-routing the sunroof drain away from the cill and then getting it filled with wax-oyl/foam/foamy-grease or some thing to inhibit rust in the cill area?

As further *****, the MOT runs out today, (I thought it was in three weeks), so I have to address this first and can't get straight on the welding job, so the car will not be ready with it's new interior for Gaydon this year as there are too many jobs to do.

I hope the time before the MOT gets finished is enough that someone here will give some advice or if you are a welder (!) near South UK offer to do the job for cash!

Regards

Ivan

farrell · 9th July 2008, 19:15

Hi Ivan
Alot of the cars go in this area.
Does not seem to have been helped by careless jacking in the past.

Just get the rotten areas cut out & get it plated.
I would return the drain outlet for sun roof / A pillars to roughly the same area.
Once you have rid of the rot, then wax oyling internally & underseal externally.
If it's neat, it will hardly notice.

A little OT.
I remember an Electronics Engineer I used to know 20 yrs ago, was really
in love with his 100 Audi Avant with a sunroof.
Decided he knew better than Audis body in white chasis Engineers.
Went on the rampage with the good old Waxoyl.
About 3 years later, his roof started to blister like a spotty teenager.
Dozens of the little things.
Turns out that his over exuberant applications had extended to the "A" pillar cavites &
double skinned roof.

The thing blocked with laying water & salt from winter use.
The summer heat did its thing & hey presto, the roof was rotten as a pear.
= Technical writeoff & no warranty claim.

Imagine the scene in the car park as a dozen male Engineers pi55 themselves
laughing.

Do it right, do it once.

Mmm-Five · 9th July 2008, 19:39

Just buy another, there are plenty for sale. Although dog knob red is 'not common' I'm sure Faz & I can source you some parts from a similar vehicle

farrell · 9th July 2008, 19:44

Yep, Buckles bangers would be able to supply lots of mint doner parts from the comfort of it's heated, fur lined garage.

Sebring NL · 9th July 2008, 21:27

Ivan

It needs to be cut away about half an inch in excess of the rotten area or further if there is a good opportunity to mate with an existing piece of metal ( hard to explain in words, but basically you want to prevent the car from looking like a puzzle)

It is indeed very thin and it would be wise to drill a hole in the 'new' piece that will have to be made to fit, through which you'll be able to put some cosmoline/waxoyl/tectyl with a U-shaped nozzle in order to spray the back end of the new metal.

Let them be very careful that the car doesn't go on fire.

Also, they must be extremely careful that the car doesn't go on fire.

Very much worth looking into is to prevent the car from going on fire.

Teamsreth · 9th July 2008, 21:57

Quote:

Originally Posted by Sebring NL

Let them be very careful that the car doesn't go on fire.

Also, they must be extremely careful that the car doesn't go on fire.

Very much worth looking into is to prevent the car from going on fire.

This would not be a good thing then?

richardbaxter · 10th July 2008, 00:32

Ivan

This area went the sameway on my car, except that in addition you may find that the lower area of the jacking point may also be missing (through corrosion)

As Farrell mentions cut it out and replate - fortunately (perhaps) this whole area is concealed from view - the inner floor edge (by the carpet and the outer cill by the body kit).

Therefore it does not need to be the prettiest repair so long as the rot is removed.

day · 10th July 2008, 20:47

Don't try to replace the floor to sill join with an "L" shaped section - this won't add any great strength (but may fool an MOT man!) and it will simply trap more water an accelerate further rot. As said above you need to cut out to good metal and butt weld new sections in.

I'm tackling mine this weekend. Looks like I will be needing a small piece in the inner sill and floor right next to the jacking point. New section is on order from BMW for the outer sill/jacking point to make a proper job of it.

The sill covers certainly give a false sense of all being well as it was only after removing mine and attacking the jacking point itself with a hammer that the rot revealed itself. As has been said before it looks like a weak point on the cars and looking at a few E34s in the scrap yard there seems to be surpisingly little rust protection in there.