Rear Sub-Frame

[Wilko58]

I'm about to change or upgrade (not sure which route now I've read some project threads!) the bushes and suspension on my Zed but I also saw a post with a picture of the boot area in someone's Zed almost rusted away (rear beam mount?). Three of the spot welds on the boot floor of my Zed (a 2.8) are showing signs of rust - a garage had a look and told me to clean it up, add some kurust and paint it over - should I just do that or should I be worried about the rust and it needing some serious work? Cheers.

 

[Grumps]

@Lee would be by far the best man to advise on this mate. Sure he'll be along later

 

[the Nefyn cat]

Just gone fully Powerflex on mine, feels much nicer and properly planted. Having said which, the rear beam bushes were totally gone, about an inch lift with the centre steel bit totally detached from the rubber part. Makes it a bit noisier inside with the roof up, but that's best avoided anyway. Luckily mine has a nice solid boot floor, and I'll be keeping an eye on it in future.

 

[Rudyrov]

Hi Wilko 58, is this the issue or related to the issue you are addressing;
https://www.bimmerforums.com/forum/...bframe-trunk-floor-differential-mount-failure

 

[Wilko58]

Hi Wilko 58, is this the issue or related to the issue you are addressing;
https://www.bimmerforums.com/forum/...bframe-trunk-floor-differential-mount-failure

Unfortunately yes, I've added some photos. I can't get any underneath at the moment.

 

[Wilko58]

Well I've sent a letter off to BMW Customer Services - let's see what they say (I know it's 19 years old but only done 86k miles) - they can only say no or words to that effect

 

[Brian H]

Not sure you will get anywhere with BMW but worth a try, the issue you have needs to be addressed with some welding, not as bad as you may think so don't worry too much, there was a number of cases like this a while back on the forum and a garage that was good and reasonably priced at the repair, hopefully someone will remember where?

 

[t-tony]

If it were my car I would use a "spot-weld" drill bit and drill from the top which would cut out the weld and leave the lower part of the joint in place.

http://www.ebay.co.uk/itm/Spot-Weld...315187?hash=item1c26b27a33:g:20cAAOSwxg5XyVgC

Then use a Mig welder to re-weld the top layer back to the bottom layer and grind flat again. Then repaint the repaired area.

Tony.

 

[Wilko58]

If it were my car I would use a "spot-weld" drill bit and drill from the top which would cut out the weld and leave the lower part of the joint in place.

http://www.ebay.co.uk/itm/Spot-Weld...315187?hash=item1c26b27a33:g:20cAAOSwxg5XyVgC

Then use a Mig welder to re-weld the top layer back to the bottom layer and grind flat again. Then repaint the repaired area.

Tony.

Cheers @t-tony - do you mean have it seam welded and on the top or underneath?

 

[t-tony]

If it were me I would just plug weld on each of the spot welds. By drilling off the top layer you will have a 6-8mm hole to fill with weld and that should be stronger than a "spot" weld. A spot weld is created simply by crushing two pieces of steel together with 2 electrodes and passing an electrical current through the steel till it melts the two layers (fuses them) together in one small spot. Hence the name.

Tony.

 

[Wilko58]

Cheers @t-tony - I'm going to take the subframe off so I'll be able to give it a good clean and make sure that the box profile hasn't got rusty inside (the spot welds are rusty so water has got in somewhere) or at least fill it with rust cure and waxoyl! Thanks for the advice, will save me a bit of money going that route.

 

[t-tony]

Cheers Tracey, but talk to Martin Scott? first, he's had more experience than I have.

Tony.

ps. If you've got the rear axle subframe out then maybe it would make sense to seam weld round the mounting.

 

[Wilko58]

I'm calling him on Tuesday

 

[Wilko58]

Not sure you will get anywhere with BMW but worth a try, the issue you have needs to be addressed with some welding, not as bad as you may think so don't worry too much, there was a number of cases like this a while back on the forum and a garage that was good and reasonably priced at the repair, hopefully someone will remember where?

BMW replied and didn't tell me to take a hike! I've got to have it inspected by one of their local agents so taking it to them today due a report to be done and then see if BMW will do anything.

 

[Brian H]

BMW replied and didn't tell me to take a hike! I've got to have it inspected by one of their local agents so taking it to them today due a report to be done and then see if BMW will do anything.

Brilliant news, fingers crossed for you

 

[NZ00Z3]

The broken spot welds are an indicator of weld failures that are hard to see on the left where the cross beam meets the main chassis rail. You need to fix that too or you will be back there welding the spot welds many more times if you only do the spot welds now.

Good luck with the repair.

 

[Wilko58]

The broken spot welds are an indicator of weld failures that are hard to see on the left where the cross beam meets the main chassis rail. You need to fix that too or you will be back there welding the spot welds many more times if you only do the spot welds now.

Good luck with the repair.

Cheers. I'll see what BMW say but I'm not confident in their ability to fix it to be honest - the BMW bodyshop I took it to had never seen the issue and was basically bewildered as to the solution and said that he didn't think they (the bodyshop) would get involved as they are very busy with accident repairs.

 

[Dickymint]

I have rusty spot welds over the whole car, I think it happened after spot welding and before spraying top coat maybe they got left out in the rain? either way I have found the rust to be minor surface rust and easily rubbed down and painted over, for a permeant fix I use Epoxy mastic from rust.co.uk, I'm planning to strip off my sills and wings ect and spray them with Epoxy mastic as a first coat just to be sure the rust wont come back, i'm even using some epoxy surfacer as a couple years ago I painted a old rusty metal post with the stuff and it still looks like new and even with some abuse its not been chipped.
I do have a plan If I can get a couple of sills cheap to make some moulds then make some in carbon fibre with a nice clear gel coat over the top not that I have done anything like it before but I saw someone make a mirror cover on you-tube and it looked really nice but I digress sorry

 

[Wilko58]

@Dickymint the spot welds on my car have all cracked so are not holding on to any metal so need a bit more than rubbing down - I wish it was that easy lol! There's a guy called Martyn Scott down in Kent who has fixed my type of damage many times before - strips and cleans the underside, removes all rust, re-welds the spot welds and then adds a strengthening plate on top so might try him if BMW don't do anything.
I've already had the wings and sills done. There's a new metal protector out that can be painted over, although I don't think it's a smooth surface, called Piranha I think - it's designed use was for truck beds but it's so strong it's being used for all sorts including military applications so it might be worth a look at?
I had a friend who could make some fibreglass sills up but needed a minimum order of 10 to proceed (cover the cost of the mould) and I asked on this Forum but only had one person say they were interested. There is a guy in Belgium who does them but won't post to the UK due to the cost. Good luck with the carbon fibre.

 

[Wilko58]

Well, as expected BMW are going to do .... nothing so I'll be sorting it out myself (or getting someone else to do it). I've talked (messaged) @Martyn Scott to death and lily going to him to get the work done but not sure to what extent yet.