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I had suspected that the space between the rear wing and inner outer sill would be accessible once the rear seat and panels were removed from the car. This is one place where the dreaded tin worm gets to do some pretty horrible damage.
As I have much of the interior trim removed, I was able to inspect that space with a usb 'endoscope' camera. It is definitely not HD, but here is the view from where the front of the LHS rear wheel arch meets with the sill:
The grey lava-like goo is some form of foam sealant, which runs down the wheel arch and continues forward along the along the sill:
While it looks suspiciously like a layer of rust flakes, I checked by extracting a few pieces and prodding with a length of copper house wiring, and the bits are a combination of the foam degrading and general detritus that has dropped down there over the years. The foam still has some elastic properties remaining but will doubtless turn to dust in time.
It is clear that if water gets in there (possibly from failing inner/outer rear wheel arch sealing), it has no way to escape:- the foam makes the section completely blind. I have no idea why Jaguar elected to do this.
Everything still appears fine after 22 years, but now is an ideal opportunity to at least do something. I'm minded to pour some engine oil in there and leave it to do its stuff. It will likely destroy the foam but I can't see what value it adds in the first place. Am I missing something?
Last edited by michaelh; 08-24-2020 at 05:03 PM.
Reason: correction
Crikey that’s concerning – especially for those with convertibles!! Looks like it’s only got the ‘body in white’ dip coat. No paint got in there...
Indeed. Primer only and a nuance of wax about 1 micron thick. Pathetic.
Originally Posted by PKWise
Are the endoscope views through the aperture in Green arrow or Blue arrow? Or, are these both access to the same void?
The shots were taken via the rear aperture:- blue arrow. The green arrow void is the 'B' post down to the outer sill, and, at least in my coupe, quite separate. It also has magic foam squirted in there:
There is actually a drain built into the rear sill jacking point underneath this area, although I can't tell exactly what it drains. I imagine it is the outer sill, so no help for the rearmost part.
I have a few days before the headlining et al are done (at least, I hope it's only a few days) so I might remove the seat belt mechanism and do some more prodding.
Built-in obsolescence under the guise of NVH engineering?
My MGB has a similar triple-layer arrangement forward of the door, but at least it's easily accessible via the removable splash guard.
michaelh,
These voids are a risk for all XK8’s. Looking at the mating panels in the vicinity, they seem all shaped to efficiently channel water and converge it all into a very effective collection point! The interior panels were spot or stitch welded as opposed to continuous seam. So once water is near, it will find it’s way...
I’m surprised this isn’t a common tin-worm area (perhaps it is?). When you look at the potential sources for routed moisture/rainwater ingress, many seem very unlikely and I suppose this is why the majority have fared well. That said, the Coupe has slightly better chances. Check this out:-
michaelh,
These voids are a risk for all XK8’s. Looking at the mating panels in the vicinity, they seem all shaped to efficiently channel water and converge it all into a very effective collection point! The interior panels were spot or stitch welded as opposed to continuous seam. So once water is near, it will find it’s way...
I’m surprised this isn’t a common tin-worm area (perhaps it is?).
The foam in these cavities is part of Jaguar's sound abatement technology. This is one of the reasons that Ford purchased the company as Jaguar is very good at this aspect of luxury engineering. It involves reducing sympathetic vibration more than blanket insulation.
The foam is closed cell which means that nothing gets through it or is trapped behind any surface to which it is bonded. Consequently water will not easily travel past it to a place where it cannot dry out.
A good way to understand the assembly of the car, its weaknesses and how to put things right is to find an auto collision repair shop that follows OEM repair procedures. They pay to have access to the manuals provided by the manufacturers showing how to replace, weld, bond, seal and restore coatings, including sound deadening, to the panels. It is amazing as one can see where an area is meant to drain or stay open. Many panel techs, including very good ones, are not often aware of these small details. I am sure that if you are willing to compensate or build a relationship with one of these shops, they would be willing to print out some of the data.
On this note, i do not think that these cars have the inside out rot like the sixties and seventies American convertibles and other rocker rotting cars where the cowl drained into this cavity. Sorry for no pictures, but follow along. If you look at the quarter panel wheel curve in front of the rear wheel and follow it to the bottom something will become apparent. The outer sheet metal which forms that nice shelf which catches dirt and moisture is slightly upturned in a lot of cars in the area before the jacking point or at least very close to level. At the underside of the rocker where it is flat is an open edge where it is possible in many cars to insert a piece of paper or the straw from a spray can. This can be probed in many cases all of the way to the beginning of the outer curve and a varying distance fore and aft. Yes, there is variation among cars. Even in unmolested samples i see a variation in the space. This space allows water to enter the outermost layer of the construction due to a capillary effect. Once it brings some salts with it, the area never dries out. Looking at this and repairs on rust damaged specimens tells me that the rusting problem is an outside-in problem from this raw flat edge under the car.
Any water that might infiltrate from the top as a convertible is well drained and serves a flushing type of benefit as long as it comes out. Please be careful with spraying coatings as once drainage is clogged, pooling occurs.
There is a rubber plug in the rear wheel well that provides access to the area of the quarter leg where internal rust is a concern. A camera can be used here as well as a rust proofing hose or wand.
To clean out the open seam in front of the rear wheel requires approaching from the back side of the rocker turn. I recommend gently probing with a spray straw. One person used a dental water pick to flush out the grit and sand. Once dry, a good gel-like rust proofing spray twice a year which will work its way into the turn.
In all of the cars where i have seen rust that have foam and seam sealers in what looks like a valley or panel bond the corrosion never started because water came in from the top and "sat" there on the foam or sealant. It came in from the outside where two pieces of sheet metal joined flatly together and the capillary effect pulled the water into the void below the sealants. Yes, pooling water above often lands in the carpets, makes a stink or screws up other things and seems like it caused the rot, but it coexists with a situation where dirt is getting into crevices from the outside and working its way in. Wheel wells are often a series of spot welds along the rolled edge of the inner well, sometimes with a sealant between them that is weld-through material. Since the bond is not continuous, water and salts get past this edge and fill the void between the inner seam seal and this outer edge. The rest is rust. This is why spraying a creeping type rust proofing gel inside the wheel well edge works as it slowly works its way into this seam by gravity and through imperfections.
I recommend two products. Eastwood here in the states makes a carbon black rust preventative meant for clean or lightly rusted surfaces. With the aerosol cans they provide spray tubes which are great for coating interior panels. Does not make a mess. For a maintenance preventative I like the Corrosionfree product. It is very effective, clear and does not make one feel that he just ruined his car. The aerosol cans with the spray straw are perfect for the small areas described above. I made a kit by modifying the tubes provided by the Eastwood product for spraying this into inner spaces until i obtained a dedicated application set from the company.
Feel free to ask any questions. Once I complete a move, hopefully next year, I am going to reach out to a Youtuber who is doing some great work and see if he would like to make a presentation based upon what i learned about these cars in terms of rustproofing.
Note that for winter driven cars, heated garages or those that maintain temperature above freezing are the enemy as salty water now flows and house humidity is drawn to the salts. Also, mild acetic acid drives out the salts and is a good way to flush areas prior to treatments as long as they can be thoroughly rinsed and dried.
Hi Cor,
Thanks for taking the time to write such a full and informative response.
I guess I should preface this by saying that I understand that Jaguar's key objective would have been to fulfil the requirements of NVH *for the projected life of the car*, rather than outcomes twenty or thirty years down the line.
I haven't had time to do anything other than a quick revisit to the rear quarter, and I can't yet determine what the drain by the jacking point services. I can poke a wire from below and it travels some inches without resistance (and I can't see it with the camera) so most likely the outer sill and no help here.
The foam sealing the gap may stop water getting down there from the top, but it also presents a barrier to air circulating to dry things out.
It's possible to gain access to the outer sill via the bung in the wheel arch, but not to this narrow rearmost outer cavity. I intend to puncture the foam to get look below if possible once I get in there again.
Your point about blocking drain holes is well taken, and is one of the reasons why I considered engine oil rather than something that solidifies.
I'm hoping my retrimmed pieces will be ready shortly so I'll ask about the OEM repair procedures. They mostly do classics but may have access to the mfrs. info.
I can't find any exploded views of how this area fits together, so here's XKRacer's shot again as it gives some clues:
No drain for that rearmost section until the sill rots out??
one of the mistakes that people make is due to losing orientation between inside and outside the vehicle. Note that i am saying this based upon other cars and have not had a chance to investigate this one for verification.
If you poke a hole in the foam and sealant at the inner panel bottom V, what often occurs is that it is right on top of the structural pinch welded vertical sheets that make up the reinforcement that goes all of the way down to the jacking points. The way to investigate this in a non-destructive fashion is to find an interior reference point, establish a plumb line next to the vehicle and measure the distance from this interior point to the jacking point. Once the math is done, it is possible to landmark the location on the inside panel.
It is better to drill a sideways hole through the foam covered vertical outer side to insert a light and your camera.
One day i am going to find a completely wrecked sample without corrosion and cutoff the forward section of the rear wheel well essentially removing the end of the rocker for everyone to see. Prior to this it might be a good idea to contact Jaguar heritage for some schematics and diagrams.
That awful picture that you just posted appears to be from outside-in corrosion. Most people do not realize what a persistent devil salt is. In the marine environment we have equipment rated for water tightness. Ok, open up the triple gasket-ed seals and one can see how the salt crystals just from the environment, not ever splashed or immersed, form a crystal bridge all the way into the interior. Once this happens, they wick moisture into the interior. On a car driven on salted roads or at the beach or near sea air, well that answers a lot of things.
Regarding the motor oil stunt. I have done this. One little thing can happen. If any of the oil drips out, especially if deposited in an area of the rocker that drains through the jacking points, it is deposited in front of your rear wheels. It is a lot of fun in the rain. And one should not dump oil until one sees the inside in total and clean. Once you make it black and dirty in there, it is near impossible to see with a scope. Corrosionfree and other products are cheap, no need to make a horrible mess or risk getting killed on a rainy day.
08-23-2020, 05:33 PM
Rear lower wing/sill rot points
