Hi there,

I’ve got a couple of questions about the underside of the jag!

I’m about to get the cat up on axel stands and get the underside cleaned down and waxed. The car isn’t to bad underneath as treated sills etc last year and a lot of the original factory underseal is still holding up well!

I’m doing the following using bilt hamber products;

-totally pressure wash the underside, then use surfex HD which is a cleaner to get it spotless.

-rub down everywhere i see any signs of rust to bare metal using a cupped wire brush on the drill, if it’s easy enough I also want to remove all the old underseal as I’ve got time.

-apply deox gel which Is a rust remover and not a converter, this when done should leave totally clean steel

-clean down with xylene

-apply electrox (zinc paint) to underside including suspension subframes, undercarriage and wheel arches

-apply epoxy mastic over the undercarriage and wheel arches but not subframes as am worried it will make undoing bolts etc hard in the future

-apply dynax ub (firm wax) to all of the underside and arches

Now to the question I have!

I want to use dynax s50 (wax) in the sills and any closed areas and cavities, it comes with a long spray Lance and stays soft. I’m going to spray this in the sills from the front when the mud guards and arch liners are out, I’m also going to remove the tread plate strip and drill a hole into the sill to inject it in, then plug it, I guess there is nothing inside the sill that could be damaged?

Where else should I be spraying this, I see rails running the length of the vehicle with holes in, I guess spray it in here?

I don’t know the underside well enough yet to know where to spray it. I see under the car there are big round plastic bungs roughly in line with the back jacking points both sides, a bit like giant corks, what are these ? Somewhere to spray?



Sorry for such a long post, all I really need to know is where do I need to spray into the chassis to protect it, an undercar diagram would be great or an explanation of where the cavities I can fill with wax are located.



Thanks in advance for any help!

 

I am going to guess the plastic bungs you refer to are the drain holes used in production.
When the body goes through a dip process these holes let excess fluid back to the tank.
The bungs are added at a later stage.
John.

 

Thankyou, so is it worth spraying any cavity protection in there or will that be into where wiring and Carpet/trim could be damaged?

 

You might want to consider whether you really want to remove the treadplates, as they are held down by adhesive tape, and it is very difficult to remove them without damaging them.
Drilling a hole into each end of the sill from inside the wheelarches would let you insert the long spray lances. which should be capable of reaching the entire length of the sill. Doing it this way and putting rubber bungs in the holes means that it is easy to repeat the process from time to time.

 

OMG... when I saw the title of this post, I thought that somebody was posting some information about going to the dentist. LOL!

 

Hi and thanks for the replies!

i managed to get the tread plates off with ease, I heated the end with an iron then slid a Stanley blade all the way along until the tread plate just popped up!

i have another question, under the bonnet there are central box sections which run each side of the engine, are these called the chassis legs? I wanted to know is it safe to spray cavity wax in here or are they full of electrics etc? I see there are many fixings to it and pre made holes, do these legs run the length of the body and will spraying wax in here damage any electrics or anything?

I hope I’ve explained clearly the part I mean,
thanks in advance.

 

I have always thought of the legs as the assembly that holds the shocks and the coil springs the hubs and wheels.
The box sections on each side of the engine could be considered the chassis rail.
I am not sure if these are bolt on sections or if they are welded at the firewall.
I would doubt if they contain any electrics as replacement would be difficult.
Have a check before you start that you are not going to hide / cover anything.
John

 

There are definitely no cables or any other components inside the chassis legs, the sills or any other box section. Here's a few pictures of a naked shell which may help you in your project (this is an XJ8 shell but 99% the same)

 

Thankyou b1mcp, those photos are really helpful!


The red circle is the section I was referring to, there is slight corrosion on the outside but nothing to bad, I see lots of things attached to it but from what you say I should be fine to spray cavity wax inside? Are the areas marked in blue connected internally to the areas in red as don’t want the wax spraying everywhere haha?!

i also have another question, under the boot roughly under where the battery is there is a hole, this isn’t where the breather pipe goes as I can see a rubber grommet at the right of the boot for that, this is directly under where the battery is but it can’t be seen from the Interior as the battery sits on a raised metal platform.
It looks like some sort of drain hole or something, it’s rusty so was just going to clean it up then wax it as it’s not Structural, just rusty and a screwdriver pushes into it a bit, any ideas what it is?

thanks again for the photos and help guys.

 

Under the car in roughly this area is where I mean?

 

Sorry I can't remember if the chassis rails are blanked off. But spraying inside them will do no harm. The areas marked in blue don't contain anything so you should treat them also. The steering column comes through the blue hole on the left of the picture but will not be damaged by a bit of cavity wax.

The hole in the boot floor you refer to is probably just a drain hole from manufacturing. There are lots of holes in the chassis that allow the shell to drain after it has been dipped during manufacture and these are just plugged or covered later.

 

Thankyou very much, all very helpful information!

i am just about to start putting wax in the box sections today and then coat the chassis, am I Ok to coat the brake and fuel lines in the wax I’m using, there is slight corrosion on both and the underbody wax I use has corrosion inhibitors ?

 

Yes, absolutely do the fuel and brake lines.

 

Just reviving an old thread!

I treated the underside of the car last year with bilt hamber dynax ub and s50 in the sills. One area I missed would be the doors, where and how should these be treated? Door inserts out and pained? Thanks for any help!