Still getting to know my TDV8 and been underneath it to look at general condition, prop, oil leaks, gaiters, drive shafts, suspension etc.

The car has done 138k miles and there is a lot of surface rust on the chassis, air tank etc. When comparing to my D3 (well, her D3 really ) which has done 189k miles, the RRS looks somewhat worse.

I did a bit of research on the forum and elsewhere about underbody protection, and see CSK Automotive mentioned a few times for many Land Rover models, for what I believe is a reasonable price (£560 for what they call the big daddy, which includes cleaning, rust inhibitor, box section internal treatment, and underbody treatment).

Has anyone on the forum got experience of this or other similar treatments, in particular what it looks like after a year or two?

From my experience of Defender and D2, the internal box section treatment would seem important for longevity, but I am assuming that the external protection might be something that needs doing every few years.

Any thoughts appreciated

Have you considered doing it yourself? I only ask because I've done the underside of mine and it really isn't a big deal. You can split it over a few sessions doing a section of the underside at a time. Quite cheap on the tools side of things too, all I needed to buy was a steel brush, some isopropyl alcohol, a can of rust converter aerosol spray and finally a can of waxoil.

Just wirebrush the hell out of the area to get the surface rust off, clean it with the alcohol and paper towels (you will need a lot) spray the rust converter and wait 4 or so hours, then finish off with a coat of the waxoil seal. All in you can get all the stuff you need for under £50 and all you need is a sunny weekend.

I did mine without jacking the car up either, just put it in extended offroad mode

Thanks for the tips.

I must admit I have considered doing it myself. I once did the rear floor pans on an Alfa GT 3.2, and I think that convinced me that someone else doing it would be more appealing, due to the mess!!

I haven't got the tools to get inside the box sections either which I think are probably important. Maybe its a case of someone do it the first time then I can top it up every couple of years.

Out of curiosity and pardon the ignorance but what do you mean by box sections?

No problem.

The chassis rails are complete boxes (unlike H beam or C section that some inferior brands have

Means that water/dirt/salt can get in, and when the factory protection starts to go, there is little you can do to reach and resolve.

Treating these from end to end with corrosion inhibitor and then protection, using a spray tool which you insert, feed through, then drag back while spraying the appropriate treatment helps stop them rusting from the inside out.

More generally, and mostly enclosed cavity might be referred to as a box section, or in Land Rover's case, a rust trap.

I see what you mean, I don't really worry that there's much rust inside there because the only way in for water is on the underside of each box section at the jacking points. Which also act as exit points for any water buildup. Ultimately it's your car and your decision though so you have to do what's right for you

There are actually a large number of water entry points on the chassis. many of them small, but water traps never-the-less.

You are right that unless the car is immersed, water getting in should be minimal, but water getting in isn't the entire problem. if the metal is not protected well (although I believe LR dipped their chassis' in several protection preparations), salt spray, general humidity etc will work away at the metal over the years.

If the car has been off roaded or used to launch boats, then possibly more serious issues long term. I think the D3/4 and RRS chassis are pretty tough though.

My concern with my car is that there is a lot of surface corrosion on the outside of the chassis rails, and a fair amount on the body underside at the back end. The car has 130k miles on it and I can compare it to my D3 which has almost 190k miles and is in much better condition. it does make me suspect that the RRS has been used to launch boats, or at least been in a harsh winter climate with a lot of salt on the roads (it was originally sold in Scotland). So rather than watch it rot from the inside out (which is what my Defender did before I got hold of it and used it to practice my MIG welding), I might as well get it protected properly.

True that, and to be honest the quoted price is far, far lower than fixing it after the fact so thinking about it as an insurance policy isn't a bad shout at all.