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Has anyone else encountered these rivet like studs holding their undertray on? Went to do the oil change earlier and came unstuck at the first hurdle! For context:

If I remember rightly, there are 3 bolts securing the front of the tray to the bumper undertray. In your photo I believe you have already removed these.

Working backwards, there are 2 bolts (1 in each of the holes in your photo). The rivets shown must not be removed, as these attach to a metal mounting bracket that the '2 bolts' pass through.

Working backwards again there are another 2 bolts.

Finally (on the rear edge of the tray) there should be another 6 bolts - 2 each at the outer edges and 2 at the rear (centre).

Good luck removing them without any snapping or just rotating.

A nasty job getting undertrays off that may not have been removed for a while. Corroded fastenings are a nightmare. The tray has to come off to get at the sump drain and also the oil filter.

I got so naffed off with my undertray that I`ve removed it completely. OK the underside of the engine gets a bit mucky but at least if you need to do maintenance in a hurry, you don`t need to have the additional fight of getting the accursed tray off. My car may not be so aerodynamic as the complete car, but at least I can get to prime components without difficulty. It also makes recovery of dropped spanners a bit easier. The just fall on the floor instead of disappearing within the tray never to be seen again.

Practicality over aesthetics every time for me. I can`t be doing with hassle now that I`m officially recognized as a grumpy old git ( or worse).

Mike

If I remember rightly, there are 3 bolts securing the front of the tray to the bumper undertray. In your photo I believe you have already removed these.

Working backwards, there are 2 bolts (1 in each of the holes in your photo). The rivets shown must not be removed, as these attach to a metal mounting bracket that the '2 bolts' pass through.

Working backwards again there are another 2 bolts.

Finally (on the rear edge of the tray) there should be another 6 bolts - 2 each at the outer edges and 2 at the rear (centre).

Good luck removing them without any snapping or just rotating.

Fantastic help, thanks very much!

I only had real difficulty with a philips-head screw which had rusted in place! No amount of WD40 was going to shift it so I carefully chiselled around it and the undertray came down!

There was some coolant drips greeting me upon its removal; this would explain me having to top it up every few weeks (from just below Max to Max). I'm always paranoid that it'll suddenly lose it's coolant so I always carry around a 5L tank of coolant and 5L deionised water, just to be safe!

I attempted to 'tidy' up the mess as best I could. The gearbox oil cooler pipes were covered in an oily grease, hopefully that's not anything to worry about.
After peering up through the engine, I could see no sign of any coolant leaking at all, however I might invest in some radweld or similar to put my mind at ease!

Thanks once again Mike for your input, I'm in two minds as to whether to leave it off or not.. It was an utter pain to get to; took me two afternoons in the end! If there were some quick-release bolts you could get for it then that would be handier than using the half-rusted items holding it up at the minute!

There is a clip and screw kit on eBay.

However the clips in the kit are stainless but the bolts are not! Mild steel!! Another mixed metal brew waiting to corrode solid. The answer would be to get the kit, then obtain some appropriate decent A4 stainless bolts.....But the issue doesn`t end there as anyone who had had to remove one of these trays will testify. Some of the bolts go into chassis members with the nuts being mounted on plates which are riveted to the chassis. The problem is that the nuts spin in the plates so it is out with the angle grinder again to moller your bolts off. That done, you then have to deal with the captive nuts on the plates. To my knowledge replacement captive nut plates are not available as parts from JCP. On the basis of that, you will end up having to make your own alternative fastenings. Getting a tray down can be a total nightmare. That is why mine has stayed off the car.

To change the oil filter and access the sump drain screw requires the tray to come off. On one occasion I managed to tease the front down by drilling out those large rivets only to find someone had earlier managed to get the wriggly metal mounting bar down from the sub-frame. No doubt he had become exasperated and got the front of the tray released in the quickest possible manner. This at least allows you to get at the oil filter. As regards the sump plug...well I gave up more fighting with the tray to access the plug and vac extracted the oil via the dipstick. Later I got the tray off which meant I could drain down from the sump plug. Sometime back I resolved that I would cut filter and sump plug access holes in the tray and eventually fix the thing back up again. That hasn`t to date and the tray lurks in the garage somewhere. That is where it can stay.

Mike

I too have been having issues with the undertray (XJR). Mine was cracked and sagging towards the rear. Last week I unsuccessfully managed to fibreglass the undertray, in the cracked areas.

The fibreglass took and stiffened up the tray however it didn't stop the sagging, which has been catching on speed bumps, both before and after attempted repair.

Today I cut it just behind the central screws (angle grinder) in order to retain the engine undetray but ensure no more sagging and grounding issues. I was careful to avoid any pipes or electrical wiring.

I should have taken some photos. I will next time. Time will tell if it's a permanent solution or if I'll inevitably end up removing as it appears many have.

A few well placed cable ties might also be useful. My XJR is held together with them. Much easier to deal with than corroded fastenings!

Mike

The cable tie must go down as one of mankind’s genius inventions. The uses they are put too are endless....some may even be used as cable ties!