Citroen 2cv special tools     |     home

price £250 hire only
you need a lathe to be able to
succeed in accomplishing this
Repair service is available.
Contact me.
£60 per hub, to include,
new threaded top hole,
steel cap
pin spanner.
King pin top grease cap modification

King pin top grease cap

Screw caps can be made of  Steel or Delrin.      
The king pin top grease cap has been a problem for us since time immemorial. Caps fall out and get lost, they don't get fitted correctly, they leak grease and get pushed out, refitting incorrectly can lead to damage to the top bush housing where the plug fits and sometimes I have even seen them welded into position, you try to make the cap shape more concave with a big ball bearing and an appropriate sized socket so it can go into its hole and be seated, and it nearly always leaks or gets pushed out, so it has been a big problem. Even the most skillful of mechanics and fitters may get it in correctly, but an owner doing his greasing routine will dislodge it with too much pressure............ It would have been a far better design if Citroen had made a screw thread at the top, like at the bottom, instead of a pressure fit cap.
I have been able to create a 25mm x 1mm x 4mm deep screw thread in this area and have also made the screw plugs, aided by athin Delrin sealing ring, to finally eradicate this grease leakage and plug security problem.

If the top of the cap area or the inside diameter has been damaged, then, it must be cleaned up to the correct size inside again to enable the tap to start  to create a thread correctly. I use a tool with 6 cutting flutes with tungsten carbide inserts.
It is 24mm diameter [the same as the existing hole] and needs to be kept central to the hole. The are various guides to achieve this. One guide fits into the 21mm hole in the hub if the top bush has been removed. The next 17mm guide fits into the bush itself, if it is left in the hub.
It's better to remove the hub from the vehicle and work on the bench. Remove the top and bottom bushes, remove the 2 oil seals, remove the ring nut and wheel bearing and give the hub a thorough cleaning.