The surround round the fuel filler cap is held by six bolts into captive nuts. The nuts sit loose in a soft plastic collar at the top of the filler neck, so once a bolt has seized in its nut, the nut turns in the plastic and the bolt just spins. On a car with its original bolts that is common. One owner hit it when he wanted the cap and surround anodised, and was left with two bolts that only turned.
Treat this as a fuel system job. Keep sparks and flames away, and do not drill or grind near the filler neck with fuel vapour about. If the tank is nearly full, expect fumes. Drilling the heads off rather than working at the nut still risks the paint around the surround.
Getting the bolts out
- Hold the nut. The nuts are reachable from behind, through the engine bay or up through the wheel arch, depending on which bolt is spinning. Holding the nut with a spanner or socket may be enough to let the bolt come out. Expect to need a second pair of hands.
- Free the ring. One owner levered the ring away from the neck to put pressure on the remaining nut and bolt, and that freed the bolt from the nut. It might work on two stuck bolts that are next to each other.
- Penetrating oil on the threads from behind, taking care not to run it over the paint.
- Drill or grind the heads off. If a bolt will not budge, take its head off and push the stub and nut through. Drilling the head only helped partly: two owners found the bolt ended up just turning with the drill, and one went on to drill out the threads. A rotary tool was suggested as a way to remove a head without damaging the surround.
- Do not pull on it hard. Once the bolts are out the surround may still be stuck to the cork gasket under it. Prise it off.
One owner got four of six out, one with a spanner on the nut, and two were left. They were the top right pair as you face the filler, which he could not reach from behind. All six were eventually drilled out.
Refitting
- The nuts are plain M6. If you push the old ones out, new ones can be popped into the plastic collar, or the old ones bonded back in with an adhesive such as Tigerseal. One owner bonded one back and had no trouble.
- Rivnuts. The owner who could not get at the last bolts drilled out the holes in the plastic flange to suit a 6 mm alloy rivnut, which went in without trouble. The neck has enough play to move it around a little, which helped. He then used stainless hex bolts. It is one owner's fix, and the thread does not say how well it has lasted.
- Gasket. The cork gasket often breaks up on removal, and one owner's was in almost five pieces. See the parts list for the number quoted, and check it before ordering.
- Replacement surrounds. One owner priced a new one at about £30 on an auction site. A black one from a VXR is more. A surround from the Lotus has eight bolts, not six, with a different hole pattern, so it will not fit.
If you are working on the filler neck anyway, see the fuel vapour system guide and the Pro-Alloy tank fitting guide.
Help wanted
We have no spanner or socket size for the captive nuts, and no photo showing how to reach the top right pair. If you have done this, please tell us the size and where you got in.