Rust proofing the underbody and the inner body

Thank you all very much for your opinions, and especially to zookbob for providing the link to another forum discussion.

Do others agree with Riccy's opinion that there is no point in coating the floor in the cabin and no point in removing the fuel tank?

Is it hard to loosen the bolts which attach the body to the chassis and jack up the entire chassis a bit (in order to gain better access to spray under the car)? How much can it actually be jacked up from the chassis before things like the steering column, pedals, wires etc. become the limiting factor?

For the inside i would just keep it clean, and probably just a polishing wax

Jacking the body is pretty easy. You can get it about 4 inches higher than it normally is by only undo-ing the brake bias thingy from the chassis rail. any more than that requires steering column, brake lines at front (or calipers off wheel hubs) and a load of wiring.

This is based upon having fitted 2" body lifts to two different jimnys (2006 and 2007). They are easy to get the height needed for that, to try bigger body lift would mean more jacking, and more stuff to undo

4"/102mm should give enough space to get at the floor above the fuel tank for spraying underseal easily.

Dont forget to have a look at buzzweld as well (you would think i worked for them!)

p.s. there are only 8 bolts that hold the body onto the chassis. They have metal tops (which cant be seen normally) on the rubber bushings at all the mounts. If you lift the body you can access these bushes top metal parts (is the only way to get to them).

These rust really badly (esp on my trayback project jim). I am convinced the corrosion of these bush top parts is the reason for the rust around the bodyshell at these points, so anything that can be done to protect them would be essential in my opinion.

I have significantly revamped the wiki article on rust protection based on my findings in the meantime.

There are still many details left "unexplored" though.

I would the others to read the entire article and contribute or suggest any corrections and improvements.


Some areas which need additional clarification:
1. Which type of primer paint is the best (etch, epoxy, acrylic, zinc, etc.)?
2. Do zinc sprays or pure zinc paints have any useful role (and which role) in rust protection?
3. Which main stone chip coat type to use (bitumen based, plastic based, polyurethane based, etc. etc.) considering long term durability and anti-cracking and delamination resistance?
4. Should anything be applied over the main stone chip coating to protect it from cracking later on (applying wax over it sounds logical to me ...)?
5. Is it wise to seal rubber grommets / plugs from body cavities with raw rubber after returning them back into position after waxing the cavities?




Apart from this, I have questions (primarily for Riccy) regarding jacking up the body from the frame:

In general, this is an excellent and theoretically simple idea, as it provides access to the top of the chassis and to the body above the fuel tank, transfer box, etc.
However, if want you jack up the body by say 3-4" (8-10 cm), what obstacles do I have to remedy first in order to perform the jacking up? What about the gear box and transfer box levers in the cabin, foot pedals, steering column, hand brake cables, vacuum hoses, brake lines?
Bear in mind that the entire vehicle would be in the air on a vehicle lift (so the axles would hang in the lowest position, and the body jacking should be applied at the same time. Will all cables and hoses be able to reach the wheels?


Also, how to perform the jacking up? Remove each bolt, then remove the bush and place a wooden brick in between, or (I have no idea on how this is to be done)?

Bosanek wrote: Apart from this, I have questions (primarily for Riccy) regarding jacking up the body from the frame:

In general, this is an excellent and theoretically simple idea, as it provides access to the top of the chassis and to the body above the fuel tank, transfer box, etc.
However, if want you jack up the body by say 3-4" (8-10 cm), what obstacles do I have to remedy first in order to perform the jacking up? What about the gear box and transfer box levers in the cabin, foot pedals, steering column, hand brake cables, vacuum hoses, brake lines?
Bear in mind that the entire vehicle would be in the air on a vehicle lift (so the axles would hang in the lowest position, and the body jacking should be applied at the same time. Will all cables and hoses be able to reach the wheels?


Also, how to perform the jacking up? Remove each bolt, then remove the bush and place a wooden brick in between, or (I have no idea on how this is to be done)?

OK, so to jack the body off the frame I have followed the instructions for installing a body lift kit (and this allows easier access in the future as well once installed).

I found it easiest to separate the body whilst on flat and level ground. Support on axle stands instead of the tyres. If a post lift is available position ready under the chassis rails (around the radius arm mount area), otherwise its crawling about under it with the paint.

Firstly you need to disconnect or loosen a few things;

Remove front and rear bumpers. headlights and sill plastics as this makes it possible to see the body bolts.

The front brake pipe inside the passenger side wheel arch has a clip on it where it exits the body into the arch about 100mm down the pipe. slide the clip out and free the pipe out allowing it to move up/down freely. Driver side (UK RHD) and rear are from the chassis rails so not a problem.

The brake bias thingy located on the driverside chassis rail near the clutch cable adjuster has to be un-bolted from its bracket to allow up/down movement.

Wiring connectors roughly where the handbrake adjustment is need removed from the body or unplugged.

Steering link under bonnet from steering wheel to power steering box needs the bolts at either end loosening (dont remove them as they are a pain to get back in!).

Check ABS sensor cables are not going to get pulled tight as this will damage them. Vac lines also at risk to front axle.

Gearstick knobs and gaiters may need removed but theres enough room on the two ive tried without that. Clutch, throttle, handbrake, etc all seem to be ok or have enough slack in them.

Finally, undo all 8 body mount bolts and start jacking. 6 underneath and 2 under the headlights.

For jacking i found the towbar was convenient at the back and the chassis legs at the front worked ok with a bit of wood between them. dont try and jack on a rusty point tho! Keep checking all around the body and engine bay for anything getting tight or pulling as you jack a little at a time. The factory jack is really handy as it fits in tight spaces well

Wooden blocks can be used between the chassis body mount brackets and the body mount pins themselves. Only half of the mounts need to be supported at any one time while working (outer 4 then inner 4). Wood is the safest material as it compresses slightly which stops it from slipping off.

Roughly 100mm/4" can be got between the two, making any work much easier. Make sure to pull the body mounting rubbers down or off as they are a trap for water and rust where they touch the body. Its a bit of a stupid design when you see it! All the factory sealant stuff that is on should ideally be removed as that's another bad one for trapping water/causing rust. Most factory welds will also be rusty or starting. Sills have rubber grommets for access which are worth removing and putting some cavity wax into. Think there is something similar on the rear body crossmember as well.

Refitting it pretty much as above in reverse, but as said, a 2" body lift kit on at the same time makes future maintenance much easier