mahon257 Posted January 22, 2009 Share Posted January 22, 2009 Looking for a bit of help! I'm mid-way thru replacing the rear-body-crossmember on my 300TDi Disco. Whilst stripping down the car, noticed a few large cracks/holes where the rear chassis cross beams meet the main chassis beams (sorry about cr*p description - photos attached should help). I'm all geared up with a MIG welder, and a locally based skilled welder chap to do the welding, but my question is: The cracks are about 6mm wide - I'm told too wide to "fill" Can I simply plate over the cracks? Would it have to be a seam weld (to seal all edges of the plate) - or would other types of weld suffice (i.e. plug welds) Any advice much appreciated, I love this old banger - really want to keep her going! Cheers Quote Link to comment Share on other sites More sharing options...
Dave W Posted January 22, 2009 Share Posted January 22, 2009 You can patch over them (in this case maybe a piece of angle iron ?) and it will need to be welded all the way around. It's difficult to see from the picture, is the hole in the chassis leg or in the end of the cross member ? As with all these repairs the extent of the damage is likely to be much larger than the visible area. You'll want to take a screwdriver/hammer to the area around it and find out how far it extends before you find something solid enough to be worth welding to. Quote Link to comment Share on other sites More sharing options...
mahon257 Posted January 22, 2009 Author Share Posted January 22, 2009 You can patch over them (in this case maybe a piece of angle iron ?) and it will need to be welded all the way around.It's difficult to see from the picture, is the hole in the chassis leg or in the end of the cross member ? As with all these repairs the extent of the damage is likely to be much larger than the visible area. You'll want to take a screwdriver/hammer to the area around it and find out how far it extends before you find something solid enough to be worth welding to. Thanks for the reply Dave W, The hole is in the end of the cross-member. It's the same story on the other side (looking at the car from the front to back). Fortuntately, the top/bottom edges of the join are fine - it is only the vertical edges - on the cross member itself. Quote Link to comment Share on other sites More sharing options...
Dave W Posted January 22, 2009 Share Posted January 22, 2009 Thanks for the reply Dave W,The hole is in the end of the cross-member. It's the same story on the other side (looking at the car from the front to back). Fortuntately, the top/bottom edges of the join are fine - it is only the vertical edges - on the cross member itself. If I remember correctly that cross member is really thin, much thinner than anywhere else on the chassis. Patch it up then fill it with waxoyl Quote Link to comment Share on other sites More sharing options...
Les Henson Posted January 22, 2009 Share Posted January 22, 2009 If you have a crack 6mm wide, I would be inclined to close it up before repairing it. That's one hell of a distortion of the chassis when you measure the effect at the crossmember ends. Holes in general can be plated over - just make sure the plate is big enough to go back to good, thick steel. Les. Quote Link to comment Share on other sites More sharing options...
stevegibbs Posted January 22, 2009 Share Posted January 22, 2009 I think les has a very good point here, if that crack is 6mm then 1000mm away you could have a big problem. Have you tried jacking the rear up to close the gap? And really clean the area before welding. Quote Link to comment Share on other sites More sharing options...
billyloadsamud Posted January 22, 2009 Share Posted January 22, 2009 All MoT repairs have to be seam welded all way round if it is a patch, if it is a replacement panel, IE; cut out the whole of a wing, sill etc, and are replacing complete part then can be welded as original, ie sills spot welded, wheel arches spot welded, etc (but only if full part replaced not repaired) The MoT for structure states no corrosion causing perforation within 30cm of a seatbelt,braking,suspension, steering or suspension mounting point Billy(MOT tester till last year) Quote Link to comment Share on other sites More sharing options...
drkwack Posted January 22, 2009 Share Posted January 22, 2009 As Les says crack that wide may well lead to other chassis suspension problems,As a fabricator/welder myself I would get hold of as many standard measurements as poss then make sure your chassis is as close as can be before you or your mate do any welding,best of luck Quote Link to comment Share on other sites More sharing options...
Dave W Posted January 22, 2009 Share Posted January 22, 2009 It doesn't look like a crack from the pictures, it's just corroded through in a vertical line. The only thing that cross member supports is the fuel tank, it's not part of the structure of the chassis as such, unlike the cross member the A frame mounts to. That's why it's made of thinner steel than the other cross members. Quote Link to comment Share on other sites More sharing options...
mahon257 Posted January 22, 2009 Author Share Posted January 22, 2009 It doesn't look like a crack from the pictures, it's just corroded through in a vertical line. The only thing that cross member supports is the fuel tank, it's not part of the structure of the chassis as such, unlike the cross member the A frame mounts to. That's why it's made of thinner steel than the other cross members. That makes a lot of sense Dave W. The metal in this cross member is like tin-foil! Really thin (I had a trial run at welding a small hole on the other side - the metal just evaporated!) If, as you suggest, it's only job is to support the fuel tank - then that explains alot... Cheers for that. Quote Link to comment Share on other sites More sharing options...
stevegibbs Posted January 22, 2009 Share Posted January 22, 2009 I think les has a very good point here, if that crack is 6mm then 500mm away you could have a big problem. Have you tried jacking the rear up to close the gap? is it a gap or a hole? its a lot thinner there. And really clean the area before welding. Quote Link to comment Share on other sites More sharing options...
mahon257 Posted January 22, 2009 Author Share Posted January 22, 2009 I think les has a very good point here, if that crack is 6mm then 500mm away you could have a big problem. Have you tried jacking the rear up to close the gap? is it a gap or a hole? its a lot thinner there. And really clean the area before welding. Just to be clear, I think this is a hole, caused by corrosion - rather than a stress crack. The rest of the chassis is intact, and the car drives just fine. It's a bit hard to tell on the pictues I know, but a poke with a screw driver caused a fair degree of further collapse. The metal on this cross-member, I would guess, is about 0.6-0/0.8mm thick. Really thin, so as Dave W suggests, I would be surprised if this beam is structural. I'm not an expert - but the feedback from other members I think is leading to this conclusion. My plan is to fold some 1.6mm sheet metal, and weld a corner patch... hopefully that should do it. When I'm done I'll be posting pictures of the rear-body cross member replacement - seems to be a common failure - which so far I've only seen documented on a Range Rover! Oh - and many many thanks to all of you that have replied... I'd truly be stuck without this forum. Quote Link to comment Share on other sites More sharing options...
stevegibbs Posted January 22, 2009 Share Posted January 22, 2009 It’s hard to tell from your pic but is the left hand chassis higher than the right or is it the way it’s sitting on the ground Quote Link to comment Share on other sites More sharing options...
mahon257 Posted January 22, 2009 Author Share Posted January 22, 2009 It’s hard to tell from your pic but is the left hand chassis higher than the right or is it the way it’s sitting on the ground The driveway is at a slight angle... The car is on axle stands purely to give me a bit more room underneath! She is sitting on brand new Police Range Rover heavy duty springs as well as new britpart shocks. oh - and for anyone curious - the red plastic bags inside the rear springs are an air-lift kit ( I guess most people in this forum would know that! just thought I'd mention it). All this extra suspension work was needed mainly to support extra fuel and water for desert travel - as attached photo from Sahara last year. Quote Link to comment Share on other sites More sharing options...
stevegibbs Posted January 22, 2009 Share Posted January 22, 2009 Good luck with the rebuild i look forward to your write-up, it’s a job I’ve put off before now. Quote Link to comment Share on other sites More sharing options...
Les Henson Posted January 23, 2009 Share Posted January 23, 2009 If it's just a corrosion problem, then an angled plate from the crossmember to the chassis will sort it out. Go a couple of inches in either direction to make sure you are welding to decent metal. Les. Quote Link to comment Share on other sites More sharing options...
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