Newbie MX5 repair.

[markimark]

So my 2003 MXNB2 has already had the chassis beams and rear sills done by the pros. Now this cost me nigh on 3k in total and now it's STILL not all there. The car passed it's MOT but I knew that lurking under a thick black layer of underseal from previous owners there would be crusty rot on the floor pan non structural bits.
So after putting the car on axle stands and cleaning the underside thoroughly with pressure washer and 3 solid days of grinding and wire brushing...it turned out not as bad as originally thought. But I did find 4-5 holes. Namely front floor rails corrosion but on non structural parts. These are reinforcent sections. One hole was near the fuel rails (!)towards the rear near the end of the floor rails.
I have a shipping container as a workshop.
My question is am I getting too ambitious trying this? I've done a 1 day course already in Mig. The course tutor said to make sure you fully drain the fuel tank...this sounds easy but how exactly should you do this...Sifon it out with a pump? Do I need to change the filter afterwards? I know to use a welding blanket and I've been told that you can simply unclip the fuel lines from the area being welded and covered it with a blanket. I'm a bit worried about fire...I've got a C02 fire extinguisher also....
Any tips would be very welcome..Im inclined to think this is a bit of a stretch for a beginner. I work as an engineer mond so I'm not a complete idiot.

 

[Nederlands]

show us a few pictures off your thin plate welding

 

[addjunkie]

Re the fuel tank…it is vapour that ignites, if its fully drained the tank is left full of vapour. If your really worried replace the vapour with an inert gas like mig gas. Or fill with water.

Investigate if repair panels are available, they are for many jap classics.

Welding on a bench nice clean metal is very different to thin rusty stuff lying under a car. Practice you thin sheet techniques before you hit the car.

 

[bricol]

Yes, I would say as a newbie to welding, that is too much. Underside welding is way more hassle than nice, neat, right way up on clean, flat, well lit metal on a bench.

I must admit I would not like working in a container - too confined both for fumes, crap from grinders and the not much space if you need to exit from underneath quickly.

Strangely, a full petrol tank is safer than an empty one. One empty of liquid is full of vapour ready to go bang. A full one only has the area of the filler neck of vapour.

If it was me though, having to weld near the tank, I would remove it - although I know on an Mx5 that would require an awful lot of work.

 

[daedalusminos]

Your biggest fire risk will be the interior trim. You will need to remove anything flammable on the other side of the floor. You may find it easier working from inside the car which will mean removing most (all) of the trim anyway.

it depends how close to fuel tank you're welding. Be wary of catching fuel/brake/wiring with the cutting disc. If in doubt remove them along with the tank.

 

[Misterg]

Hello and welcome!

Is it the fuel lines circled in yellow that you're worried about when repairing the hole on the right of the photo?

If so, *I* wouldn't be worried - the fuel lines are steel, and the tank is sealed - it vents through the charcoal canister into the front subframe, and they're the other side of the chassis rail.

I think that hole will need repairing from inside if you want to get all of the rust as it extends over the chassis rail.

Welcome to the money pit :-/

(Oh, and that hole in the front may well be the tip of the iceberg - ask me how I know )

 

[johnik]

as someone who has spent countless hours laying under rust buckets, i would say it is a bit of a bridge too far for a beginner.....oh and someone put your steering wheel is on the wrong side as well.

 

[minimutly]

Lying underneath and getting rained on by sparks, spatter, melting or burning under seal (by far the worst thing) is not much fun. Doing it in a shipping container - no thanks. I would get an engine hoist, push the car outside, lift it up and weld it outside.

 

[Blobber]

I think you have a lot more cleaning to do before you see the full extent of the repairs required, as for trying to do that sort of work in a shipping container

 

[Smallfry]

A LOT of work there. Existing metal needs to be clean of ANY rust, paint, and underseal to weld properly, or it will just blow holes.

Fuel lines can just be covered, but I would be inclined to remove the fuel tank. Not just for safety, but for access. To do any jobs like this, you need to be comfortable. Not trying to weld at arms length, not being able to see properly with you hands wobbling.

Of course a beginner can do it, but it takes a lot of time to get a good result. It is worlds away from practicing on a bench. Ideally, the car should be on a rotisserie. It is far easier to get at, and far easier to get satisfactory results.

 

[dave h 2]

The carpets at least have to come out as does all the under coating/sound deadening.
You need the open up the holes till you get paint on both sides which will give you the full thickness of metal to weld to.
Rust doesn't attack in an even layer so pin holes form, which your MIG will widen into a big hole.
Do not lap any repair panels it makes water traps which will need redoing in 2 years time.

There's a section for welding thin metals in the forum tutorial section.

 

[bricol]

If I remember correctly from breaking the one I bought for bits, the rear sub-frame needs to come out to get the tank out.

 

[Jelly_Sheffield]

The course tutor said to make sure you fully drain the fuel tank...

DO NOT in any circumstances drain the fuel tank inside a shipping container, that you later intend to weld in. DO IT OUTSIDE!

Also in many ways draining the fuel tank but leaving it in place, unpurged is just as dangerous as leaving it full (differently dangerous, but still dangerous), if it's genuinely so close to your welds that there's an unavoidable risk of being damaged and causing a fire or explosion then just completely remove it and store outside (even though it's a lot more disassembly), otherwise protect it fully with blankets and you will be good.

this sounds easy but how exactly should you do this...Sifon it out with a pump? Do I need to change the filter afterwards?

The fuel filter sits below the tank level, disconnect the fuel filter and the fuel will gravity drain...

I discovered this by draining petrol onto my face trying to change a fuel filter, but I recommend you use a funnel and a jerrycan!

Do change the filter when you reassemble, it's like a few quid, does help keep the engine running smooth, and I guarantee you don't want to do it with a full tank.

I'm a bit worried about fire...I've got a C02 fire extinguisher also....

Having one is better than none, but if you're worried about a flammable liquid pool fire, you need Foam...

CO2 will cope with a small flammable liquid fire, but not one that rapidly spreads out over a wide area (like burning petrol is prone to doing).

My question is am I getting too ambitious trying this?

That depends on your aptitude and your willingness to try, fail, pick yourself up, and try again... A Lot.

I've done a 1 day course already in Mig.

...

Im inclined to think this is a bit of a stretch for a beginner. I work as an engineer mond so I'm not a complete idiot.

I used my work training budget (also an engineer, they wouldn't let me put additional money in to use it for an MBA so I figured **Language** it let's do something fun) to do my C&G Level 3 Diploma in fabrication and welding, and a specific pipe welding course to prepare for doing "coded welder" certificates...

Even with hundreds of hours hands on welding time in the college workshop, doing genuinely tricky welds to a high standard...

I was in absolutely no way prepared for trying to mig weld 0.8mm or 1mm steel, with varying degrees of corrosion, upside down, on my back, in a confined space, wearing a leather monkey mask.

Automotive repair welding is a completely different skillset to anything you're likely to cover in college, and will rely a lot less on the welding (assuming you have the basics), and much more on your ingenuity, fabrication skills, and ability to think round problems.

You will only learn those skills by trying, everyone was a beginner once.

 

[markimark]

Thanks to everyone for their valuable tips. So I'm not gonna try and do it inside the container...as recommended. It turns out there is a slightly more experience colleague at work who is willing (with a bit of cash and beers) to show me and he also has a full workshop. So probably the best way..
This weekend I took out the carpets and inspected the rust holes from.inside and they could be a lot worse..

 

[Jackimus]

Thanks to everyone for their valuable tips. So I'm not gonna try and do it inside the container...as recommended. It turns out there is a slightly more experience colleague at work who is willing (with a bit of cash and beers) to show me and he also has a full workshop. So probably the best way..
This weekend I took out the carpets and inspected the rust holes from.inside and they could be a lot worse..

Always so good to have a friend!

 

[markimark]

show us a few pictures off your thin plate welding

Like I say...I'm a complete novice!

 

[markimark]

DO NOT in any circumstances drain the fuel tank inside a shipping container, that you later intend to weld in. DO IT OUTSIDE!

Also in many ways draining the fuel tank but leaving it in place, unpurged is just as dangerous as leaving it full (differently dangerous, but still dangerous), if it's genuinely so close to your welds that there's an unavoidable risk of being damaged and causing a fire or explosion then just completely remove it and store outside (even though it's a lot more disassembly), otherwise protect it fully with blankets and you will be good.


The fuel filter sits below the tank level, disconnect the fuel filter and the fuel will gravity drain...

I discovered this by draining petrol onto my face trying to change a fuel filter, but I recommend you use a funnel and a jerrycan!

Do change the filter when you reassemble, it's like a few quid, does help keep the engine running smooth, and I guarantee you don't want to do it with a full tank.


Having one is better than none, but if you're worried about a flammable liquid pool fire, you need Foam...

CO2 will cope with a small flammable liquid fire, but not one that rapidly spreads out over a wide area (like burning petrol is prone to doing).


That depends on your aptitude and your willingness to try, fail, pick yourself up, and try again... A Lot.


I used my work training budget (also an engineer, they wouldn't let me put additional money in to use it for an MBA so I figured **Language** it let's do something fun) to do my C&G Level 3 Diploma in fabrication and welding, and a specific pipe welding course to prepare for doing "coded welder" certificates...

Even with hundreds of hours hands on welding time in the college workshop, doing genuinely tricky welds to a high standard...

I was in absolutely no way prepared for trying to mig weld 0.8mm or 1mm steel, with varying degrees of corrosion, upside down, on my back, in a confined space, wearing a leather monkey mask.

Automotive repair welding is a completely different skillset to anything you're likely to cover in college, and will rely a lot less on the welding (assuming you have the basics), and much more on your ingenuity, fabrication skills, and ability to think round problems.

You will only learn those skills by trying, everyone was a beginner once.

Thanks for this really helpful. Yer I need to change fuel filter anyway so I guess letting it drain is easiest way...course making sure nobody has a cigarette while it's busy draining

 

[markimark]

The carpets at least have to come out as does all the under coating/sound deadening.
You need the open up the holes till you get paint on both sides which will give you the full thickness of metal to weld to.
Rust doesn't attack in an even layer so pin holes form, which your MIG will widen into a big hole.
Do not lap any repair panels it makes water traps which will need redoing in 2 years time.

There's a section for welding thin metals in the forum tutorial section.

Yer I got that...see new pics. Anymore visibility I'll have to take centre console out although removing the dash appears not strictly necessary assuming I can temporarily pin the carpet up to the steering wheel/ gloves box and stuff welding blankets underneath and on top of the floor if welding from underneath

 

[markimark]

Hello and welcome!

Is it the fuel lines circled in yellow that you're worried about when repairing the hole on the right of the photo?

View attachment 511446

If so, *I* wouldn't be worried - the fuel lines are steel, and the tank is sealed - it vents through the charcoal canister into the front subframe, and they're the other side of the chassis rail.

I think that hole will need repairing from inside if you want to get all of the rust as it extends over the chassis rail.

Welcome to the money pit :-/

(Oh, and that hole in the front may well be the tip of the iceberg - ask me how I know )

Haha...it's already hoovered up 3k but then I didn't pay a lot for the car in first place....
Anyway, yes your assuming correct. Fuel lines are other side of rail as circled. I got access to under the carpets today to get a full assessment. It could be a lot worse...

 

[markimark]

Re the fuel tank…it is vapour that ignites, if its fully drained the tank is left full of vapour. If your really worried replace the vapour with an inert gas like mig gas. Or fill with water.

Investigate if repair panels are available, they are for many jap classics.

Welding on a bench nice clean metal is very different to thin rusty stuff lying under a car. Practice you thin sheet techniques before you hit the car.

Yer luckily the MX has very good spare parts available..

MX-5 NB-FL Steel panel & panel fittings

All products from the category: MX-5 -> Spare Parts -> Bodywork / Chassis -> Steel panel & panel fittings

www.ilmotorsport.de