Rust proofing the underbody and the inner body

I plan to rust-proof the underbody and possibly the inner body of my Jimny, while the vehicle is still young and with very little corrosion which can be cleaned with little effort.

The vehicle has no corrosion whatsoever in the trunk floor, nor anywhere in the floor below the front or the rear seats.
The outer underbody side has started to corrode in a few places, mainly near the coil spring mounting points, near the body mounting points and on a few other places where the factory welds are.


Now, I would like to hear additional opinions on some of my ideas and doubts:


1.

Would there be any point in spraying the floor from the inner side (for example below the rear seats and the trunk floor) with some anticorrosive protective layer?

I know that these parts of the body are usually first and most affected by rust in Jimnys. However, I personally think that these areas do not rust because they are "attacked" from the inside of the cabin, but from the outside (from under the vehicle). Somebody correct me if I am wrong!

So, in my (current) opinion, the floor of the vehicle should be well protected / rust-proofed only from the outer (lower / underbody) side, and there is no need at all to spray the body floor from the inner side. Am I correct?


2.

Continuing onto the first issue, I consider the area of the body floor which is usually most endangered by rust to be the one above the fuel tank and above the exhaust muffler.
So, wouldn't it pay off to demount the fuel tank entirely (because it is the largest "obstacle") and then gain proper access to the body floor from under the vehicle in order to fully and properly spray it?
Has anyone done this for rust-proofing purposes? If they did, was the removal of the fuel tank sufficient to gain good access to the entire rear part of the body, or should the transfer case and rear exhaust muffler be removed as well?


3.

I intend to spray the interior of the chassis rails and tubes with automotive wax (if there is a better material than wax, please advise).

However, would it make sense to (somehow) rinse the interiors of the chassis tubes first? I am afraid that rinsing them with high pressure water jets would be counter productive - while it might evict some dirt out, it would take a long time to dry the interiors of the chassis rails, possibly starting the corrosion inside before applying the wax.
Has anyone done this?


4.

I know that many Jimnys develop rust just below/behind the front head lamps. However, I do not understand why this happens. I mean, no abrasive particles or substances usually reach that place (as far as I know!), so the factory paint in that place should hold the bare metal properly sealed forever.
Does anyone have a clue why this happens?
And, what rust proofing agent to apply to permanently protect this area from future rusting?


5.

I intend to spray the inner cavities in all doors with automotive wax, as well to spray the exterior body panel sections which are usually hidden below the side plastic moldings (above the wheel arches and on the lower portion of side doors, etc.). Is there anything better than automotive wax for this purpose?

1. - no point in spraying the inside

2. - removing the fuel tank is a bit unecessary, the rust tends to be around the edges, sills and footwells. following the procedure to do a body lift (unbolting and jacking it up) would give much better access to everything.

3. - clean the chassis tubes with compressed air and a vaccum cleaner with a long hose. you are only aiming to remove any loose debris or flakes of rust.

4. - water gets in behind the headlights and pools there, as well as plastic trims underneath the wheel arch causing dirt trapping.

5. - the inside of doors, panels, etc is already primer painted but may be worth getting inside the sills with cavity wax as there are access points just inside the door if you peel the carpet back (rubber grommets blank the holes). I think there are some on the outside of the sills also but you need to remove the plastic trim to get at them.

Re what to use, I would reccomend Buzzweld (www.buzzweld.co.uk) who make a range of rust control, prevent and cavity stuff. Not badly priced and works really well.

At my job we are recommended to spray underbody with transparent wax first, let it dry, then go on with the thicker underbody sealer.
If I were to buy a new Jimny today i would fill all car with cavity wax everywhere i could, and lay down underbody sealer under. But the key to having a nice rust free car, is cleaning cleaning cleaning! and polishing! At least once a year I steam my cars under, remove all plastic covers and clean. Its the dirt and salt that kills all vehicles, i see it everyday at work. Those who take car of their cars dont have these problems

I put 20 litres of Waxoyl into my Jimny using just the cheapo Waxoyl presure sprayer and plenty of White Spirit to thin it down. It worked a treat but you and the car get absolutely caked in the stuff as does the floor.
Therefore get plenty of old cardboard boxes and lay them flat under the car, Raise the car up on axle stands or similar, clean off all the dirt you can, remove the front and back bumpers, grill etc and spray to your hearts content.
Take off all the inner panels as well and spray liberally everywhere!
Job Done and peachy perfect!!!!!

I don't know if you have already seen this thread:

www.bigjimny.com/index.php/forum?view=to...d=56816&limitstart=0

Quite a bit of rustproofing discussion.

I seem to go through this every now regularly and then when I get a used motor, Vitaras, Pinin, Freelander, Pajero, Junior and many others. Last one was my new Celerio which typical of Suzuki had no real protection underneath from new.
Interior floor surface I have only done when it has seemed to need it like the back floor of a Sherpa van that had been used by a plumber or the jack well in a Jimny. Such as these get a coat of something heavy and yes it takes a day or so to dry but when dry it is rock tough.
Always I do the box sections and that will include those holding seat brackets and the like. I drill holes in the sills if I need to and in some Suzukis the sill box sections are divided. Anything tube like gets it. lol
I always do the doors and such like. Either I take off the door card or find an ingress point. The injection tube is long enough to get along most of chassis sections doors and so on. I use Waxoyl with an airline
As for floor pans on the outside/underside once cleaned/derusted they get a coating. Wheel arch too.


Views differ on what to use but I use Hammerite underseal with added Waxoyl. Areas I cannot get a brush or spray to like between petrol tank and floor I will simply spray Waxoyl. I do hood (bonnet) much the same way, box sections inject panels underseal. As a bonus we get some sound deadening.
It's a long dirty job and I often wonder if I am wasting my time especially if I don't keep the vehicle.

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