Having now found the pictures I took of the underneath of my 2000 XK8 cab when I bought it, I would like to ask members why they think it failed and whether just removing the surface rust with a wire brush and some paint would suffice or whether sections needs cutting out and replacing,
I went all along the rusty areas jabbing away with a sharp screwdriver but couldn't find or create any holes, nor did it flex or sound soft.
MOT was done in August so I doubt the testing station would remember exactly what caught their eye and I don't want the expense of insuring it just to take it for another test.
Hopefully someone will recognise the rust areas and be able to give me some advice -






(Above) Bracket and chassis securing front of rear subframe, well rusty but no holes and sounds solid when struck









(Above) Sills and wheelarches rusty but again no holes and stabbing with a sharp screwdriver doesn't create any (floorpans have been patched at some point)

Is it likely to have failed because of the appearance of rust and as there are no holes could I just remove the rust, treat what remains and paint?

Mark

 

If you tap the metal with a light hammer and it sounds good, it is likely that you could find a tester that would pass that. Mine looks fairly similar.


More info on the test can be found here. MOT UK car and vehicle MOT information equipment car servicing parts and spares - corrosion


I will be derusting that section on my car over the winter and if it is sound will paint over with epoxy mastic and underseal.




Your repair area is the driver foot well which is common and caused by a design flaw.

 

I would wire brush it, metal prep it and brush on "POR 15 chassis black".

 

I did mine about 2 months ago, used drill driver with a wire brush head and painted it with black waxoyl bought from Amazon for around 12 quid. Must say mine was in immaculate condition for its year, could have passes for a3 year old motor. The black waxoyl looks great when finished.

 

I would brush on black POR-15 rust preventative sealant and be done with it. I think POR-15 seals better if you put it over the rust. Based on memory (from nearly 20 years ago) you just get off any flaky rust and paint it over the rest. POR-15 will cover it up, keep it from spreading and it will be pretty difficult to tell it is rusted underneath at all.

 

Do that if you want to MOT the car and sell it quickly, if you want to keep the car then get rid of the rust then paint with epoxy mastic and then seal with an underseals such as Waxoyl or Dinitrol 4941M.


I have used the waxoyl underseal in the past but am moving to the Dinitrol one due to reports from others.

 

RD - Yes this is a car that I intend to keep so am looking at affordable permanent solutions, knowing full well that the best solutions are usually the most expensive.
So - I'm thinking -
Eradicate the rust (friend is bringing some phosphoric acid in on Monday) followed by Rustbusters 2 pac epoxy mastic, then dinitrol the sills on the inside, between the inner winds and arches and the floor.
But to get the bulk rust off do I use a wire brush in drill (which may just end up polishing the rust) or buy a needle descaler?
The descaler advert says don't use it on bodywork - so is it likely to damage my floor?
I also wish I could get all the underseal off - I'm sure there's more rust hiding underneath.
Thanks for everyone's replies - I am grateful for experience!

Mark

 

Yep...I did the same POR 15 and when dry over the top with chassis coat black,
one word of warning.....DO NOT get it on your skin, you'll wear it for a week if it dries on you!

POR15 Rust Preventive Paint (946ml) US Quart | Frost Auto Restoration Techniques

POR15 Top Coat - Chassis Coat Black | Frost Auto Restoration Techniques

The larger tin will do the whole underside of the car inc under the 4 wheel arches, try to do the POR 15 in one hit, leave it for 48hrs and do the top coat in one hit. You will need best part of a whole day to complete each coat.

TS

 

For rust removal I use a knotted wire wheel on an angle grinder and a power file with 40 grit.


For the bracket, I would leave in a bath of citric/phos acid for a day and then clean up, repeat as necessary until ready for paint.,


As for the remaining pitting you will need a gel to stick on the surface. As yet I have not found a really good solution for this.


I don't use rust converter any more as it only converts the surface and leaves rust beneath.


As for the Rustbuster epoxy mastic, long term tests seem to show it beats all the others.

 

Thanks to all for the helpful advice above.
I want to keep the car so want near-permanent repairs, so will work on it over the winter to try and achieve that.
I bought some 6 ton axle stands (its a heavy car!) and my plan is to get it in the garage on the stands with the rear wheels off, and find and remove as much rust as I can (I bought these to start with ).
I am also thinking of removing the rear subframe and treat that w mastic outside dinitrol inside unless there is an option someone knows of to galvanise it.
Thanks again.
Mark

 

I bet that was a seaside car..... Very crispy..... I did one recently and it did not look that bad..



After

 

Nice stainless exhaust and paint job XKracer - but what is the first photo of? the rear sub-frame?

 

My 2000 was about the same. I ended up welding in 19 plates, including the front chassis legs behind the front cross member, rear floor, seat belt mount and various other bits and pieces.

The rear A frame will probably be shot. Mine "looked" OK, until it was removed then holes were easily prodded.

The A frame brackets whare they bolt to the body can be de-rusted - an acid dip will do this. The floor mounts will need to be welded, they rot from the big plastic plug. That is probably where it has failed. it may well be that these have rotted due to bad sealing of the rear wing to inner wheelarch, so this area should be wire brushed and sealed properly before repainting.

The wheelarch flanges will not have failed it.

With respect to other posts, "covering up" rust with underseal type products is merely that, a cover up. This is OK for light surface rust, but it is the inside out rot that only accelerates when "covered up" (a local garage has a 1998 XKR for sale with a freshly black waxoyled underside hiding probably quire a lot!) I have used clear dinitrol so any new corrosion can be easily spotted should it dare to appear!

If you plan on keeping the car, suggest you remove the rear axle assembly so you can deal with all the rusty areas properly. Also the box section where the body goes over the rear axle may have rotted as the seams are not sealed. This can only be effectively repaired with the axle out. Best to really go looking for trouble, probing all likely rusty areas and welding up all that needs it in one hit, so it is done!.

Chances are chassis legs below the front spring mounts will have gone too, so front subframe will need to come out.

Might also be worth changing the brake pipes while you are at it!

 

And after all that...might be best to start over and look for another XK.

 

Better the devil you know!

 

If I had known then what I know now I would have thought twice about buying an XK8.


If I had known then what I now know about Kim's particular XK8 I would have run a mile.


If I was buying again now, what would I buy instead, with the criteria of, it must look fantastic (>= XK8/R), must have modern comforts and must cost less than 10k. Hmmm, I can't think of an alternative.


The moral of the story has to be, buy with care, probably from the south of England, but not anywhere near the coast.

 

XK8 has reached that "maturity" where at least where salt is used on the roads, corrosion will be a problem. If it can be caught in time, then serious exterior panel surgery can be avoided.

To some, it will be a case of scrapping as they may not want to spend on having all the work done.

To others, it is an opportunity to purchase very cheaply, then invest a lot of time on doing what needs to be done!

As ever there is a silver lining. Those of us who keep our cars see the scarcity driving up value - maybe not in the very short term, and with all the scrappers, it is an oppotunity to put into stock some spare parts at decent prices.

Have used a fair bit of this:
Buy Phosphoric Acid Gel Rust Remover UK Ireland | Mistral Cleaning Products
Cheap and as good as any of the other acid or similar rust removers.

 

I will give that a go, I think a lot of the modern similar gel products have become "greener" by using cirtic acid but their performance is poor, citric acid needs to be hot to work effectively on rust.


I use a suspended tea cup heater/boiler on a clockwork 24hour on/off timer to heat my bath of citric acid when needed, it works great and the citric acid powder is cheap. Great results at about 70degC, but takes ages if left at room temp.

 

heat helps.
For a "dunking" solution, try clover alloy wheel cleaner. Brilliant! 20% phosphoric and 5% hydrochloric. Nasty but effective. Don't get it hot!!!
I also tried deox -c and found it very slow, even when using a slow cooker! so it is back to the alloy wheel cleaner for me.

 

The top picture on my post is of the rear subframe, whilst the subframe was out I welded the main mount sections and chassis section in the wheel arch, waxoyled the lot before and after I refitted the frame