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 Post subject: Notorious CJ rear chassis leg rot - how to repair
PostPosted: February 26th, 2014, 9:24 pm 
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Totally Addicted to Colt!
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Joined: February 28th, 2010, 2:44 pm
Posts: 3191
Location: Norwich/North Yorkshire
Model: CJ (1996 - 2004)
: 1.8 4g93T GSR
The CJ rear chassis legs are prone to rust and rotting, a problem which I knew could be a problem for me in the near future so I decided to have a poke about. Before I took my colt off the road for all the work I am doing it had an MOT about 3 months before hand, so it is safe to assume that the rot on my car is identical to how it passed the MOT though I daresay, having left it a few more years it would have been a much bigger problem so worth sorting early.

For anyone who doesn't know where the issue is located, on my car the worst rust was located slightly behind the fuel tank on the chassis leg which runs between the passenger side upper rear control arm and the fuel tank.


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The first thing to do is remove the loose rust as much as possible using a hammer, chisel and large flat head screw driver/scraper. don't be afraid of going too far, if it will come off with these tools then it needs to come off! Then go mad with an angle grinder. You don't want a grinder that is too large, here is mine which is perfect size for the job. You will also need a full face mask, a welding mask with a "grind" function to prevent it dimming is ideal... It's a very messy job so beware! Just get laid under the car and put in some hard graft.

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After half an hour or so, you should be able to get it looking more like this:

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Once you have most of the rust removed, the key now is to pinpoint which pieces need replacing and which are still solid. As you can see in the picture above, the grinder has gone through in some places already so obviously these sections need cutting back a little more and cleaning up to a allow a solid weld.

You will also find at about this point that the legs are made up of multiple layers of sheet steel which has been spot welded together. If you are cutting a section out with spot welds, you will need to drill these out. The put a cutting disc in the grinder (I use 1.2mm slitting discs) then cut out the sections you need cutting out.

(picture mid cutting)
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A dremmel is sometimes useful to tidy the edges at this point. But as a summary, the piece I replaced, had two layers. The thick structural layer and a thinner piece which was spot welded over the top. Always replace for equal or greater thickness than the original. The easiest way is to cut pieces to size is to use cardboard.

[imghttps://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-xpa1/v/t1.0-9/1912397_10202614383694585_1407558003_n.jpg?oh=47cb49da9fa6218e3011767231f5abcd&oe=551F6D9B&__gda__=1424032836_0227ab0832a777b8d7b3f84cf7b5122c/img]

Then cut some steel to fit from the card template:
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Tack into place:
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Now I'm not a bad welder (on clean metal in easily accessible areas) but welding upside down in such a tight place, I admit was a challenge. As a result I made quite a mess! but that's what practice is for i guess. The good news is it is very solid!

Image


Luckily after the practice of the first section, I got the thinner piece over the top to look much tidier!

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Tomorrow I will get round it with seam sealer and give it some good zinc primer before a fresh layer of underseal!

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 Post subject: Re: Notorious CJ rear chassis leg rot - how to repair
PostPosted: February 26th, 2014, 9:48 pm 
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Proud Colt Owner
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Joined: January 30th, 2012, 9:44 pm
Posts: 364
Location: Gloucestershire
Model: N/A
Nice one mate looks good I just wacked a plate from a door onto it and welded it :P


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 Post subject: Re: Notorious CJ rear chassis leg rot - how to repair
PostPosted: February 27th, 2014, 12:18 am 
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Totally Addicted to Colt!
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Joined: October 15th, 2007, 7:04 pm
Posts: 2026
Location: Yardley - East Birmingham
Model: CJ (1996 - 2004)
: Resurrected 4G93
Jeez, that's nothing. I could get my fist into my chassis legs before repairing them. Took me two weeks of evenings cutting, grinding, cleaning, painting etc after work to do both chassis legs, both outer sills by the front foot wells, both rear inner wheel arches and driver side front inner wing.

But I learnt a lot of skills, and I've got a great neighbor that cleaned up some of my messier mig welding with his oxyacetalyn kit.

The car should be dead. Again. But I love that bag o' bolts too damn much.


Good work though mike! Didn't know you can buy slitting discs. They look properly handy!

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After owning my car a decade & being on MC/CUK all that time, I stand by my right to say what the hell I like!
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17" alloys fit a CJ no problem- 7j width, PCD 4x100, offset et42 & 205/40/17 tyres- TRUST ME!!


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 Post subject: Re: Notorious CJ rear chassis leg rot - how to repair
PostPosted: February 27th, 2014, 1:13 am 
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Totally Addicted to Colt!
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Joined: February 28th, 2010, 2:44 pm
Posts: 3191
Location: Norwich/North Yorkshire
Model: CJ (1996 - 2004)
: 1.8 4g93T GSR
cheers yeah they are real handy i use them all the time! like i say i knew it wasnt too bad but better do it now and take an afternoon than wait a few years and spend a week i guess!

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 Post subject: Re: Notorious CJ rear chassis leg rot - how to repair
PostPosted: February 27th, 2014, 2:43 pm 
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Totally Addicted to Colt!
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Joined: October 15th, 2007, 7:04 pm
Posts: 2026
Location: Yardley - East Birmingham
Model: CJ (1996 - 2004)
: Resurrected 4G93
True. I think once they start going they crumble like an over-dunked digestive biscuit.

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After owning my car a decade & being on MC/CUK all that time, I stand by my right to say what the hell I like!
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17" alloys fit a CJ no problem- 7j width, PCD 4x100, offset et42 & 205/40/17 tyres- TRUST ME!!


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 Post subject: Re: Notorious CJ rear chassis leg rot - how to repair
PostPosted: February 27th, 2014, 9:16 pm 
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Totally Addicted to Colt!
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Joined: February 28th, 2010, 2:44 pm
Posts: 3191
Location: Norwich/North Yorkshire
Model: CJ (1996 - 2004)
: 1.8 4g93T GSR
haha that's the perfect description! yeah mine was exactly like that but luckily confined to quite a small area. god knows what id do if there was 5 times as much!

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 Post subject: Re: Notorious CJ rear chassis leg rot - how to repair
PostPosted: March 2nd, 2014, 10:19 am 
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Started to go a bit Colt crazy!
Started to go a bit Colt crazy!
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Joined: July 26th, 2009, 6:44 pm
Posts: 560
Location: Blackpool
Model: CA (1992 - 1996)
thats a damn good write up,fair play to you dude

going to sticky this topic as it will affect every CJ owner at some point

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Disclaimer: Everything that I post on this forum I claim to be fact, through either doing it myself, assisting others directly or from 'Joe21'. Whether you choose to take my advice is your choice


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 Post subject: Re: Notorious CJ rear chassis leg rot - how to repair
PostPosted: March 16th, 2014, 9:28 pm 
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Totally Addicted to Colt!
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Joined: August 11th, 2009, 6:43 pm
Posts: 1662
Location: wales, Anglesey
Model: CJ (1996 - 2004)
: CJ V6 Mivec
I have to do mine before I put the rear evo setup on!

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 Post subject: Re: Notorious CJ rear chassis leg rot - how to repair
PostPosted: August 5th, 2014, 12:43 am 
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New to this Colt stuff
New to this Colt stuff
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Joined: August 1st, 2014, 11:04 pm
Posts: 12
Model: CJ (1996 - 2004)
god I thought my car was going to be a night mare and not worth repairing at least I know its something all colts suffer from
mine also has a hole near drivers side rear inner arch there a small bung in it that's fairly shot so will need to be plated aswell


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