Hi

Recently tried to replace a rusted through NVH brace which is secured by the front rear subframe bolts ,when trying to undo the bolts the captive nuts started spinning inside the chassis mounts .
the bolts and captive nuts are rusted solid and it is virtually impossible to get access inside the mounts , the subframe bolts are now loose , any info on how to overcome gratefully received .

Mark

x350 2007

Captive Nut Inside subframe mount is spinning

 

Cutting looks to be your only option, the best way is the real question.
Grinder with cutting disk if there is room, is easier than a reciprocating saw.
Cutting torch around the gas tank is kinda iffy.
Unless your real careful, things could go up in smoke.

 

The more i look at mine, am thinking the whole steel rear frame section will have to be removed.
Wondering just how big a job that would be, once the rear suspension, & all are removed.
If your lower brace is this bad, does rest the frame it bolts to look much better?
If the four bolts that appear to attach the frame to the body, from the drawings.
Are accessible from the trunk, it SHOULD be similar to removing the bed from a pick up truck
Not all that bad a job, after everything necessary, is disconnected, & or removed.
My 07 has this same situation starting, but not nearly as advanced as yours.
Spraying used A T F on it slows it down, but more is need to stop it.
Am looking and asking myself, as well as others, is this a project, you can do yourself???????????????
Used parts are around, blasting, then painting before replacing, would be the best solution.
Someone here, has probably already done this, and will respond.

 

If you are contemplating removing the subframe then I suggest you take a look at the rear brake pipes while you are at it.

About 18 months ago I had to have the rear brakepipes replaced on my 2004 Super V8 ( in the UK ) due to corrosion .In order to do this they actually removed the rear subframe and the fuel tank. They also found the captive nuts were really seized up, the technician spent a lot of time sorting the problem but managed it in the end. My rear Brembo callipers had seized bleed nipples so I sourced a pair of used callipers and they were swapped out at the same time.

 

Saddle fuel tank, a new fixing bolt shown, and the subframe when it was on the floor !

 

The exposed heads on all the bolts on mine look fine.
But if torque is applied and one or more were to break.
Or to break the nut loose, on the other end.
That i'm guessing is spot welded, or underneath the gas tank, of all places?
If total rear frame removal is required, is the removal of the fuel tank really required as well?
Unless i'm mistaken only the heads are visible on mine, none of the bolt is exposed.
Just realized this is inside the trunk???
Thought this was from underneath the car
That would make sense, of the picture to me
Now i see after looking at roviw's pictures of what made no sense to me.
On what the issue is

 

I can understand why roviw s technician would have spent so much time resolving this issue
The previous photograph of the seized captive nuts was through a small opening in the aluminium subframe support as shown by the green arrow in attached photo , it would seem the only way to replace the seized captive nuts is to cut the exiting bolts to allow the subframe to be dropped , then somehow get the old captive nuts out through this small opening and then replace with new captive nuts and bolts ( if new ones are available )
roviw - any clarification on the actual detail of how this was carried out when they replaced yours

Arrow showing opening in subframe mount

 

Those type of captive nuts are a nightmare, they are just a nut which is held in place by a metal "spring", once the bolt rusts up any pressure on th ebolt causes the nut to force its way out of the spring and just spin. had this a lot on ford Mondeo front subframes, and Vauxhall's, Vauxhall's were relatively easy as you can see the nut, so a bit of heat and some vice grips usually did the trick, Mondeo's were inside the chassis leg and the method i used was to cut a square out for access , then heat and vice grips, replace, and weld a plate over the hole. Lately I have an inductive coil heater which works a treat.

This looks a bit more tricky, definetly need heat, an inductive coil might help, but it looks like it would be difficult to even get it over the nut, not a lot of room there. If you could get access with a mig welder, you could tack weld the nut in place, the heat of the weld, might also help to free up the bolt. Of course if it's steel to Alu, then you have more trouble.

A few years ago, I had a ford in with siezed spark plugs, alloy head and steel plugs, so a danger of damaging the head, no movement on the plugs whatsoever, I created a little dam around the plug with plastecine/putty and filled it with vinegar, left it for a full day, replenishing the vinegar a few times, and the plugs came out like it was in finger tight.

 

Sorry but I do not have any further details as to how he did the job, the actual technician has since left my local Jaguar dealer so I cannot even pop in and ask him.
All I remember was they were telling me there was going to be a lot of extra time involved in the various work at the time. It was part of a service, MOT ( road safety test in the UK )and various other things. The car was with them a month, I had told them there was no hurry and to work on it whenever they could.
I have been using the local main dealer for 30 years and they look after me very well, so I help them whenever I can and they , in turn, help me out when the invoice is prepared.
This particular visit amassed a job sheet with 36 hours on it !!
I did supply a pair of used rear Brembo Callipers, a new hand brake motor unit and cables and a few other parts, they also provided a few new items as well.
I told them the car was a keeper so he did say he put loads of grease/copperslip whatever to minimise the nuts seizing again .

 

Got into my sub frame today and have the same problem.. Driverside nut spins. I will be following this post for updates and also asking my repair shop for ideas.

 

Sorry this has taken so long but just finished today. So my car 2004 XJR 4.2 Supercharged.
The problem: The forward left rear subframe captive nut not so captive.

Captive nut in frame. What a good one looks like
It's located in here.

Arrow points to a tab I will talk about later.

That hole is just over 2 man sized fingers wide. You can see it hanging as it Came out a little bit before it broke free.

So the cage opened and it free spins.
No room to get in there with anything. So my mechanic cut it off. Fished it out of there. Captive nut fits thru that hole but is not sold for replacement.

The arrow is the tab I spoke of in earlier photo. Opposite of that is the area the rear tab was.
What came out of there. Both pieces are steel.

I think they broke off the rear tab when they worked to get it out. Mostly because neither of us knew what it looked like in there. Once out he heated it up and took out the last bit of bolt. I tried to stay involved as much as possible to avoid any hacking. So what was done. Cleaned up the threads of the nut put it back in the cage and welded it shut and together. No pictures of the top side.

Bottom view of rear tab welded back on.

View of where the captive nut lives.
Rear tab slides into that groove in the back there.

This is a view from the bottom of where the rear tab goes. That hole in the bottom left just big enough to get a finger in.
So at this point I'm fully involved and reinstalled it myself. I put it in the hole and slid the rear tab into place. Pushed it down as far as i could but its is slightly larger at an angle. I screwed a new bolt into the nut and pried it down until the front tab engaged in the hole.

New bolts from Englewood NJ. Jaguar.
Rear Subframe Front. C2P7262. Just under $7
Rear Subframe Rear. C2P7261. Just under $10
Called all over the place they dont sell the nuts for the rear subframe just the front subframe.

So in short if you have this issue. I would cut the bolt off wherever you can get to it. Then cut it as close to the hole as you can but keeping enough to grab onto so you can remove it. Push in the front tab so it clears the hole and push the front side up. To release the rear tab and it should come on out.
I toyed with drilling a few holes and threading bolts in to try and hold the bolt section in place. But i don't like adding new holes to the car.

 

Great solution!!!

 

Just tried to undo my son’s, whished I’d looked at your pictures first, very useful pictures, thanks.
Bob

 

Hi,

I don’t suppose that you took any photos of your brake pipes? The ones on my sons have been replaced before and are a mess, including where they go behind the tank, next to the battery cable (which has previously rubbed through on the subframe when the ‘technician’ failed to put the cable back on its clip when skilfully replacing the brake pipes!

This caused a short which resulted in the current passing through the offside brake flexible braiding, melting the inner pipe and producing lots of white smoke from heated brake fluid. We fixed it at the time by sleeving the cable with plastic piping but now the subframe is out I will do proper job.

So, back to the question, any photos of the brake pipes above the subframe and behind the tank, as we don’t have much to go on!

Thanks

Bob

 

The pipes come as a set from Jaguar, still available here in the UK

Brake Pipes
You need number 4 in the diagram, Part number is C2C29560, £36.40 inc VAT, comes as a set of 2 pipes with all the clips.

 

With the alloy lines now available, its now possible to make them up yourself.
The alloy is around 95% copper, with the rest nickle, & they are stronger than steel.
They don't rust, they bend & flair easily as copper line.
Brake lines from the master cylinder, to the back brakes on my 96 Honda, several years ago.
Still stopping it when needed, going down the road
WAY CHEAPER & EASIER than how they say to do it, its your choice
Fish the lines through, flair them, then connect, its as E Z, as that.
Have fixed a few cars this way, none as complex as these are though.
With the return lines from the A B S system being the biggest difference i see.
As long as they are plumbed correctly, the lines can be routed as you wish.
As long as they are out of the way, & supported they should be fine.

 

Hello.
Yeah my lines were toast also. I had them cut back to where they run under the splash guard on the passenger side\ right side. Fittings, flares and new pipe ran to the wheels.

I also ordered new hoses to the calipers. pipe was pretty ugly at the mount end. I also had a hole in my power wire. Not sure if it was a rub thru tho. Wire was corroded inside the insulation almost a half the way thru. The fuel filler hose clamps were showing some age so changed those while in there also. I took my subframe all the way off. If you undo the drive shaft mark it well.

Hoses from car to caliper (BREMBO)
not cheap. Price 8/19
C2C6168 Brake Hose $154.52
C2C6169 Brake Hose $138.69

Tried to make them myself but could not find a proper banjo end.

 

Goodridge makes the hoses on our cars, they also sell bulk hose, & reusable fittings.
They are big in the custom motorcycles, make lines, small enough to run inside the handlebars.
Still somewhat custom to see the lines disappear into the handlebars
Look at what they have to offer, if you flair your own lines.
You can make up your own hoses, & save a lot of money..

Goodridge High Performance Brake Line Kits - Goodridge

 

Thanks Brian,

Have obtained the pipes from Jaguar and also the front to rear ones, all at a bargain price (for Jaguar parts). At that price it’s not worth making them (and you get new clips as well), they will be well waxoiled so should last for the life of the car this time!

Bob

 

I am thinking of removing my rear subframe for a thorough de rust and repaint, so a big thank you to those who have provided picturers and info earlier in this thread. I too have had to cut into the "chassis" parts on the bodyshell of my 05 x type to get the captive nut out. A TIG welder is a very effective way of applying concentrated heat to seized nuts, You use low current so the nut does not actually melt but after a while gets up to a good red heat. Are the rear nuts as accessible as the front?