Evaluation of Defender 90 chassis

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CJ7

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I am new member but I have been searching the forum , but not found
what I was looking for , so I hope I am not repeating an already vivid
debated question.

How do I evaluate the structural integrity of my chassis ?

I have stripped the chassis , and it looks solid on the outside,
however I know the story can be completely different from the inside.
It is 1996 and got a new rear member 10 years ago , There are a few
holes that has been patched up . When I knock , it has a good tone and
does not indicate signs of heavy corrosion.

I like to have it sandblasted outside and inside , How-to do that?

Would it be an idea to cut of the rear 1/4 chassis to open into the
rails , open the front and cut a hole in the middle cross member .
Then when back from blasting make inspection , and if found good , weld
it all back together.

Chris
 
Thanks , I guess it sounds very sexy with a new gal frame and there seems to be a hole industry build up around making such products . I don't really understand why it is not possible to sandblast the frame inside , if it is opened up?
anyway thanks .
Chris
 
CJ7 said:
Thanks , I guess it sounds very sexy with a new gal frame and there seems to be a hole industry build up around making such products . I don't really understand why it is not possible to sandblast the frame inside , if it is opened up?
anyway thanks .
Chris
Click to expand...
If you were to cut one side off the whole length of each chassis rail then you would be able to sand blast the inside. Then once blasted you would need to treat the inside and then you would then need to re-weld the whole length of each chassis rail once finished, and re-treat the inside to protect the weld. I think the for amount of work that would involve for a limited benefit, I would not be bothering. I would either be getting a new galvanised one, or just wash out the current one and fill it with your preferred brand of cavity wax as suggested above.
I don't think anyone is saying it is not possible to cut it open and blast it, anything is possible. However, I agree with the above consensus that is is possible not the best course of action.
 
CJ7 said:
I am new member but I have been searching the forum , but not found
what I was looking for , so I hope I am not repeating an already vivid
debated question.

How do I evaluate the structural integrity of my chassis ?

I have stripped the chassis , and it looks solid on the outside,
however I know the story can be completely different from the inside.
It is 1996 and got a new rear member 10 years ago , There are a few
holes that has been patched up . When I knock , it has a good tone and
does not indicate signs of heavy corrosion.

I like to have it sandblasted outside and inside , How-to do that?

Would it be an idea to cut of the rear 1/4 chassis to open into the
rails , open the front and cut a hole in the middle cross member .
Then when back from blasting make inspection , and if found good , weld
it all back together.

Chris
Click to expand...

I would be inclined to say that at 22 years old it is probably going to have some rot issues. Places to look are at the lowest section of the rails such as around the rear radius arm brackets at the bottom, they can rot in there right into the corner. Go along with a 4oz hammer and tap the metal listening for a dull thump rather than a metallic clank.

It depends how this chassis was looked after, if it was caught with Dintrol/Waxoyle early and done well it may be 99% perfect but I doubt that if it needed a new rear cross-member, if it was a late treatment after the rot set in then there is almost certainly going to be rot. If it has been garaged all its live and rarely got that wet or muddy it might be perfect but I would be surprised.

You cannot sandblast the inside.

If the chassis has never had internal Dintrol/Waxoyle treatment, then removing all the external paint, making any repairs, then sending it for galv should work as the internal walls will be surface rusted and the acid bath will remove light rust - you would need to be fairly sure it is not full of gunge inside though as the galvanizer will get annoyed if you contaminate his acid bath with loads of filth.

Another option is to get it acid dipped and get it back to see what holes appear, weld up the holes well then get it galvanised, but as above, if it was treated with Dintrol/Waxoyle then your not going to do very well.

Cutting a chassis apart and welding it back together is... mad.
 
Last edited:
If you look at how the chassis is built it is not simply one layer of steel made into a box section, in some places its three layers thick, so even if you cut it open you could still not get between the layers.

Take a look at this pic and you can clearly see whilst the steel is sound ish there is rust between the two layers, then note the strengthening bit at the bottom which is a third layer and theres simply no way shot blasting will get the rust out.

Screen Shot 2018-04-23 at 15.13.44.png
 
Thank you all , for good inputs and educational pictures . I guess when I am talking about sandblasting inside , it is more for the process of getting all loose debris cleaned out to bridge the way for an more durable oil treatment.
 
Plug all the holes in the chassis, fill it with the dirtiest black overly-used engine oil you can get hold of, run it for a couple of days, the rougher the ground the better, then drain it all off and dispose of it in a responsible way.
The carbon and oil will stick to the inside like shyte to a blanket, and should give you protection for quite a number of years.
That's the way it used to be done, instead of all the fancy stuff that is recommended nowadays! ;);)
 
Oldseadog said:
Plug all the holes in the chassis, fill it with the dirtiest black overly-used engine oil you can get hold of, run it for a couple of days, the rougher the ground the better, then drain it all off and dispose of it in a responsible way.
The carbon and oil will stick to the inside like shyte to a blanket, and should give you protection for quite a number of years.
That's the way it used to be done, instead of all the fancy stuff that is recommended nowadays! ;);)
Click to expand...

With the added bonus of leaving a nice oil slick on the roads ready to surprise any unsuspecting biker.
 
Oldseadog said:
Plug all the holes in the chassis, fill it with the dirtiest black overly-used engine oil you can get hold of, run it for a couple of days, the rougher the ground the better, then drain it all off and dispose of it in a responsible way.
The carbon and oil will stick to the inside like shyte to a blanket, and should give you protection for quite a number of years.
That's the way it used to be done, instead of all the fancy stuff that is recommended nowadays! ;);)
Click to expand...

Heavily used engine oil contains a lot of acid and water. It is actually a better preservative for wood than metal.
If you are going to use oil for metal preservation, I would suggest used gear oil, no combustion by-products, less degraded, and will stick better because it is thicker.
 
Get a welders pointed hammer and go all around the chassis, this will tell you how good or bad it is.
I had a 110 85 and the chassis was rotten, when I cut it open to have a look, all I saw was clean black paint or whatever it had been dipped in from new.
Latest 90 chassis was rotten inside and outside and that is an 85 as well.
 
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