110 rear crossmember Welding

congo181 · Oct 23, 2021

Hi all. Cleaning the rear of the chassis on the 110 and have found a second bit of rust that needs a weld.
It’s a bit awkward to get to, and as I’m new to auto repair of this depth, any pointers to the correct way of fixing it would be appreciated. I’m not sure how I can remove the rotten internal part without destroying a lot of the good outer skin.

This is the crossmember top and you can see where it’s delaminated from the bracket welded inside. I’ve removed the puff-pastry to see the extent.

This is inside and you can see where I’ve chopped out the really bad bit.
So it seems to me that I need to remove some of the outer skin to get to the inner part to cut it out? Or what? Not sure how to proceed with this now.

The rest of the chassis is looking pretty good!

ER1C · Oct 23, 2021

Just a thought, not sure how bad the rest is but often the best bet would surely be just to get a new rear cross member with extensions. Job done, they are thicker, stronger and better in every way. I would opt for that route. You can DIY it but the effort in fabrication etc vs the cost of of a new one.

congo181 · Oct 23, 2021

ER1C said:
Just a thought, not sure how bad the rest is but often the best bet would surely be just to get a new rear cross member with extensions. Job done, they are thicker, stronger and better in every way. I would opt for that route. You can DIY it but the effort in fabrication etc vs the cost of of a new one.

The amount of welding required to fix a new cross member in place is far greater than to fix this bit of rot. I mean yes, a new cross member would be lovely, but it’s really not required in this case, so why spend the money?

ER1C · Oct 23, 2021

congo181 said:
The amount of welding required to fix a new cross member in place is far greater than to fix this bit of rot. I mean yes, a new cross member would be lovely, but it’s really not required in this case, so why spend the money?

Hammer it out and plate it.. I am sure it will be fine..

Turboman · Oct 23, 2021

congo181 said:
The amount of welding required to fix a new cross member in place is far greater than to fix this bit of rot. I mean yes, a new cross member would be lovely, but it’s really not required in this case, so why spend the money?

I doubt if that is even an MOT fail. Just plate it up a bit and blast it with preservative or coatings of your choice.

You should get at least a decade out of that, I should think.

lynall · Oct 23, 2021

congo181 said:
The amount of welding required to fix a new cross member in place is far greater than to fix this bit of rot. I mean yes, a new cross member would be lovely, but it’s really not required in this case, so why spend the money?

Before doing anything see if you can scrounge a boroscope and take a look in the rear chassis itself, if thats sound get repairing.
Do bear in mind the x members rust for fun, and as its started!

congo181 · Oct 23, 2021

lynall said:
Before doing anything see if you can scrounge a boroscope and take a look in the rear chassis itself, if thats sound get repairing.
Do bear in mind the x members rust for fun, and as its started!

I’ve got access to a boroscope - I’ll do that.
I’m going to be doing all the chassis interiors once the outsides painted so it’ll all get a coating of something oily.

lynall · Oct 23, 2021

congo181 said:
I’ve got access to a boroscope - I’ll do that.
I’m going to be doing all the chassis interiors once the outsides painted so it’ll all get a coating of something oily.

Have peek/feel inside the chassis to bulkhead outriggers, in fact stick your hand in though the lower hole and have a feel, mine are starting to scab up.

meego · Oct 23, 2021

congo181 said:
Hi all. Cleaning the rear of the chassis on the 110 and have found a second bit of rust that needs a weld.
It’s a bit awkward to get to, and as I’m new to auto repair of this depth, any pointers to the correct way of fixing it would be appreciated. I’m not sure how I can remove the rotten internal part without destroying a lot of the good outer skin.
View attachment 251007
This is the crossmember top and you can see where it’s delaminated from the bracket welded inside. I’ve removed the puff-pastry to see the extent.
View attachment 251008
This is inside and you can see where I’ve chopped out the really bad bit.
So it seems to me that I need to remove some of the outer skin to get to the inner part to cut it out? Or what? Not sure how to proceed with this now.
View attachment 251011
The rest of the chassis is looking pretty good!
View attachment 251009

I wouldn’t mess about trying to save the outer skin because it’s in good condition. Cut right through both skins and weld in a plate of equal thickness to both. If done right dress back the outer weld flush and it will be invisible when it’s painted.

congo181 · Oct 23, 2021

meego said:
I wouldn’t mess about trying to save the outer skin because it’s in good condition. Cut right through both skins and weld in a plate of equal thickness to both. If done right dress back the outer weld flush and it will be invisible when it’s painted.

Thanks for the advice - exactly what I’m looking for. I was thinking of that approach. I think it’s two layers of 1.2mm. Do I run the risk of blasting the first skin to get penetration down to the second?

meego · Oct 23, 2021

congo181 said:
Thanks for the advice - exactly what I’m looking for. I was thinking of that approach. I think it’s two layers of 1.2mm. Do I run the risk of blasting the first skin to get penetration down to the second?

Without actually seeing the job. If you can get to both sides of the weld then weld them. If you can’t get to the underside, grind the edges of the new plate and the cut at about 30/40 degrees and you should catch both skins. I don’t know your welding skill, but the key with mig is clean metal. Even when welding new metal with mig, you get a better weld if you take the “skin” of the area you are welding.

congo181 · Oct 23, 2021

meego said:
Without actually seeing the job. If you can get to both sides of the weld then weld them. If you can’t get to the underside, grind the edges of the new plate and the cut at about 30/40 degrees and you should catch both skins. I don’t know your welding skill, but the key with mig is clean metal. Even when welding new metal with mig, you get a better weld if you take the “skin” of the area you are welding.

I’m still learning to weld, but I can do a reasonable job. Yeah I guess putting a nice chamfer on it is going to make it easier to fill into both layers.

this is a cross section and the green inserted panel is spot welded in. The red bit is where the rot is.

meego · Oct 23, 2021

congo181 said:
I’m still learning to weld, but I can do a reasonable job. Yeah I guess putting a nice chamfer on it is going to make it easier to fill into both layers.
View attachment 251033
this is a cross section and the green inserted panel is spot welded in. The red bit is where the rot is.

I can kind of see how I would do it, but it’s hard to explain. Cut enough of the top out to let you cut out the rotten top piece of the vertical green line. Weld a new piece in there, overlapped or flush, then weld your new top piece in. These jobs can “evolve” as you work through them and better ways to do them become apparent as you go. This is why I like working with metal, if you balls it up you can stick some back on

mick the builder · Oct 23, 2021

I'm sure that won't be an isolated patch of thin rusty metal. Why spend all that time and effort repairing that patch. When you've rebuilt it and in a couple of years, another patch of rust appears, you'd have wished you had put on a new rear crossmember.

congo181 · Oct 24, 2021

All sorted now. Hope my solution looks ok.
Thanks @meego for the support

meego · Oct 24, 2021

congo181 said:
All sorted now. Hope my solution looks ok.
Thanks @meego for the support
View attachment 251094
View attachment 251095
View attachment 251096

Looks great. You should be well pleased with that mate.

congo181 · Oct 24, 2021

meego said:
Looks great. You should be well pleased with that mate.

Cheers. I reckon it’ll pass muster. The more I weld the better it gets.

meego · Oct 24, 2021

congo181 said:
Cheers. I reckon it’ll pass muster. The more I weld the better it gets.

That’s a fact, and the more confident you get you will take on jobs you thought beyond you previously.

congo181 · Oct 24, 2021

It’s been a bit of a jigsaw but I’m enjoying the challenge.

discomania · Oct 25, 2021

congo181 said:
Hi all. Cleaning the rear of the chassis on the 110 and have found a second bit of rust that needs a weld.
It’s a bit awkward to get to, and as I’m new to auto repair of this depth, any pointers to the correct way of fixing it would be appreciated. I’m not sure how I can remove the rotten internal part without destroying a lot of the good outer skin.
View attachment 251007
This is the crossmember top and you can see where it’s delaminated from the bracket welded inside. I’ve removed the puff-pastry to see the extent.
View attachment 251008
This is inside and you can see where I’ve chopped out the really bad bit.
So it seems to me that I need to remove some of the outer skin to get to the inner part to cut it out? Or what? Not sure how to proceed with this now.
View attachment 251011
The rest of the chassis is looking pretty good!
View attachment 251009

Stick a new one on and be done with it:

https://www.paddockspares.com/catalog/category/view/s/to-the-end-of-300tdi/id/5456/

110 rear crossmember Welding

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