Chassis/Underside - What's your approach to surface rust removal on complete underside?

[hysteria357]

My only regret doing fairly extensive rust removal myself was not keeping a bucket of chunks to see how much metal I lost.

 

[SeventhDurandal]

Let me recommend a less labor intensive approach, based on my experience with a very rusty 2003 GMC Sierra.

1. Do all the maintenance/baselining work that you want to do now. You'll probably need that induction coil that others recommended to ease fastener removal. Make sure you do as much of this as possible before proceeding, as maintenance work after coating is extremely messy.
2. Powerwash the entire undercarriage, make sure to get deep into those frame rails and dead spaces. Allow to dry for a few days.
3. Lanolin undercoat. I suggest Fluid Film for this, as it is a little thinner than Woolwax and might penetrate better. Make sure you get into EVERY body and frame cavity. Doors, sills, fenders, quarter panels, tailgate, etc.
4. Drive it for a year. Respray the bottom once a year for a few years. You will notice that more and more rust will fall off over the months and years, revealing oily black metal.
5. Once most of the rust is gone, you can switch to Woolwax if you want. It is much thicker than Fluid Film and will hold up better; you might need a coat every other year once you've built up a base.

My (anecdotal) evidence for this is based on what I observed through a few years of spraying my truck. The pictures below are from right before I sold it, freshly sprayed and after about four years of treatments. I don't have 'before' pics unfortunately, but the frame was HEAVILY rusty (large sheaves of rust you could pull off by hand) and so was the body. As you can see there are a couple slightly rusty spots left, and some components are somewhat eaten away.

This process will never get a vehicle back to like-new, but it is a LOT less labor intensive than pulling the truck apart, and will get you 90% of the results. Working on it after this will be very messy, but the fluid film will penetrate in and you should have much less of a problem with stuck fasteners.

 

[SteveH]

I would avoid ever using any 'rubberized' coatings. All such coatings can only work if sealed against totally clean metal, and if water never (ever) gets behind them. The water WILL find a way, and then any rubberized coating acts like a poultice, keeping water/salt/rust trapped against the metal, making it rust even faster. Tar-based 'undercoating' and 'sound deadeners' fall into the same camp - do not use as rustproofing under vehicles.

As many have noted here, you want grease/oil based coatings that remain 'live' and do not cure. I'm not sure I would even attempt to paint that frame after cleaning. I would apply a grease product liberally, and flood all frame areas with ATF or ATF mixed with paraffin (heated until runny). I have literally taken axle grease from a tub, with a gloved hand, and applied to to rusty surfaces, working it into the rust and crevices. I can assure you that any rusty surface that is coated with 1/8" (ok, a couple mm for the Brits ) of grease will not rust.

Final note, no rustproofing is 'forever', so a yearly check on a lift and perhaps putting more liquid grease products inside the frame is a must.

 

[SMLE]

Hi folks,

Bumping this as I'm finally getting around to this now in the next few weeks, I've got a compressor, air blower attachments, needle gun etc ready to order.

My plan for the chassis rails etc is to blow them out as mentioned, spray with pressure washer as much as possible (leave to dry for a few days) and then using a spray attachment get lots of fluid film in them, anything wrong with this approach?

For the rest of the easier to reach stuff, I'll be blowing it all out, using a pressure washer to remove loose stuff (leaving to dry for a few days) and then using a needle gun where needed, and then spraying on fluid film to needled rust/light surface rust, sound like a plan?

I wasn't planning on applying any top coats of paint/primer etc, does this approach work okay?

I'm not in a position to bare metal this, and this isn't going to be a full restoration, I just want to get the rust under control and stop it getting worse, especially ahead of winter as our roads are salted.

Many thanks!

 

[whitec13]

Hi folks,

Bumping this as I'm finally getting around to this now in the next few weeks, I've got a compressor, air blower attachments, needle gun etc ready to order.

My plan for the chassis rails etc is to blow them out as mentioned, spray with pressure washer as much as possible (leave to dry for a few days) and then using a spray attachment get lots of fluid film in them, anything wrong with this approach?

For the rest of the easier to reach stuff, I'll be blowing it all out, using a pressure washer to remove loose stuff (leaving to dry for a few days) and then using a needle gun where needed, and then spraying on fluid film to needled rust/light surface rust, sound like a plan?

I wasn't planning on applying any top coats of paint/primer etc, does this approach work okay?

I'm not in a position to bare metal this, and this isn't going to be a full restoration, I just want to get the rust under control and stop it getting worse, especially ahead of winter as our roads are salted.

Many thanks!

If you needle gun all of it and begin an annual or semi-annual fluid film (or similar product) treatment plan, you will be set for a very long time. Getting the scale off is paramount. After that, just keep it oiled up like a beach beauty and ride her out. I unfortunately had to finally admit defeat and walk away from my 100 last week. She was literally falling apart and rust could not be managed in any capacity anymore. BUT I did sell it for $2500 to a guy for parts and only paid $4500 (I think) with $3k in maintenance over the course of 8.5 years of ownership. I can’t complain.

 

[SMLE]

If you needle gun all of it and begin an annual or semi-annual fluid film (or similar product) treatment plan, you will be set for a very long time. Getting the scale off is paramount. After that, just keep it oiled up like a beach beauty and ride her out. I unfortunately had to finally admit defeat and walk away from my 100 last week. She was literally falling apart and rust could not be managed in any capacity anymore. BUT I did sell it for $2500 to a guy for parts and only paid $4500 (I think) with $3k in maintenance over the course of 8.5 years of ownership. I can’t complain.

Thanks!

The internet suggests that the phosphoric acid needs wiping off before fluid film or similar is applied, is that other people's experience? I want to make sure the fluid film is applied as well as possible and that the underlying surface rust is dealt with too.

Sorry to hear about your 100 series, sounds like you had a decent run with it, they definitely seem to deteriorate pretty quick once the rust bites them, so I'm keen to keep mine away from that fate!

Thanks

 

[delz05]

Pressure wash and degrease as best possible first. Remove all components you are able to, including front and rear bumper covers, wheels, exhaust, and whatever suspension, drivetrain and fuel system components you can. Blowout and vacuum the inner frame rails and cross members. Begin using the needle gun, go up the outside frame rail, down the inner frame rail, switch over to the opposite side and repeat. If able drop the transmission crossmember and the spare tire carrier. Blowout and vacuum, the frame rails again. Then attack the floorboards and rockers, paying attention to the front corners behind the front wheels and the rear corners in front of the rear wheels. Check the rear quarter dropoffs, which were covered by the rear bumper cover. Once you have broken down all of the scale and corrosion, wipe down the leftover oxidation with whichever rust kill product you plan to use. Follow the directions accordingly. Some rust kill products can be primed or painted over. In any case complete that process and then prime and topcoat. That may take a few days to complete. Now once final topcoat has been applied and has cured, blow out the inner frame rails again and vacuum one more time. Then coat heavily with Woolwax. I would put on average a full quart into each inner frame rail. I would then spray the floor pans, the inner and outer rockers and all cross members. Take your time, there’s no rush. The heavier you apply Woolwax, the more protection you will give. The outer frame rails are done last and then the reassembly begins. I would spend on average between 40 -100 hours reconditioning a frame and if welding was required that number could easily double. I have dropped many frames from these bodies along with Tacomas and 4runners with excellent results. Most important is not rush it. It is very labor intensive, but the end result, if done right, is well worth it!
Good luck!

 

[SMLE]

Pressure wash and degrease as best possible first. Remove all components you are able to, including front and rear bumper covers, wheels, exhaust, and whatever suspension, drivetrain and fuel system components you can. Blowout and vacuum the inner frame rails and cross members. Begin using the needle gun, go up the outside frame rail, down the inner frame rail, switch over to the opposite side and repeat. If able drop the transmission crossmember and the spare tire carrier. Blowout and vacuum, the frame rails again. Then attack the floorboards and rockers, paying attention to the front corners behind the front wheels and the rear corners in front of the rear wheels. Check the rear quarter dropoffs, which were covered by the rear bumper cover. Once you have broken down all of the scale and corrosion, wipe down the leftover oxidation with whichever rust kill product you plan to use. Follow the directions accordingly. Some rust kill products can be primed or painted over. In any case complete that process and then prime and topcoat. That may take a few days to complete. Now once final topcoat has been applied and has cured, blow out the inner frame rails again and vacuum one more time. Then coat heavily with Woolwax. I would put on average a full quart into each inner frame rail. I would then spray the floor pans, the inner and outer rockers and all cross members. Take your time, there’s no rush. The heavier you apply Woolwax, the more protection you will give. The outer frame rails are done last and then the reassembly begins. I would spend on average between 40 -100 hours reconditioning a frame and if welding was required that number could easily double. I have dropped many frames from these bodies along with Tacomas and 4runners with excellent results. Most important is not rush it. It is very labor intensive, but the end result, if done right, is well worth it!
Good luck!

Thanks for this!

A few questions if I may:
- how are you vacuuming out the inner rails?
- are there drain holes if I'm jet washing inside the chassis through holes? I'm very conscious about it not just sitting inside and not being able to get out

I'm not in a position unfortunately to be able to remove much from it, or it be off the road for long, but I'm going to be as thorough as possible! Thanks

 

[stonepa]

Hi folks,

Bumping this as I'm finally getting around to this now in the next few weeks, I've got a compressor, air blower attachments, needle gun etc ready to order.

My plan for the chassis rails etc is to blow them out as mentioned, spray with pressure washer as much as possible (leave to dry for a few days) and then using a spray attachment get lots of fluid film in them, anything wrong with this approach?

For the rest of the easier to reach stuff, I'll be blowing it all out, using a pressure washer to remove loose stuff (leaving to dry for a few days) and then using a needle gun where needed, and then spraying on fluid film to needled rust/light surface rust, sound like a plan?

I wasn't planning on applying any top coats of paint/primer etc, does this approach work okay?

I'm not in a position to bare metal this, and this isn't going to be a full restoration, I just want to get the rust under control and stop it getting worse, especially ahead of winter as our roads are salted.

Many thanks!

This is what I have done for 28 years with my 100, which spends its life less the 100 feet from the North Pacific in Alaska. Zero rust on the frame, suspension, or body panels. Fluid Film just plain works.

 

[delz05]

With the bumper covers off, it is easy. I would set the vacuum hose into the frame rail from the rear and securing it with duct tape. I would then work the air nozzle from the front of the vehicle, working my way to the back using the open frame holes. Vacuum will be on as you do this. Two sets of hands makes the job easier.
After washing out the frame, use the airline to blow the water out of the frame. I would then let it dry if possible for 24 hours.

 

[SMLE]

With the bumper covers off, it is easy. I would set the vacuum hose into the frame rail from the rear and securing it with duct tape. I would then work the air nozzle from the front of the vehicle, working my way to the back using the open frame holes. Vacuum will be on as you do this. Two sets of hands makes the job easier.
After washing out the frame, use the airline to blow the water out of the frame. I would then let it dry if possible for 24 hours.

Thank you, this makes sense!