After cleaning and refilling the rear dampers inevitably they end up leaking from the front seals, you could decide to replace them with “Reconditioned” ones but you can’t be sure the seals are in good condition. After some thought I have devised a way of replacing the front seal with an off the shelf standard oil seal, some aluminium flat sheet and an O ring. It also involves the use of a router, a pillar drill and a 20mm hole saw. The method I have used is the same as the rear Half Shaft Oil Seal.
Before posting this I have already repaired and road tested one damper and it shows no signs of leaking.
First off, with the damper removed or if you have a damper that has leaking seals, clean and drain the damper.
Next you need to mark on the damper arm some reference marks to aid disassembly and reassembly. Sorry about the quality of the pic but you can see the marks on the damper body and the damper arm, they indicate the two extremes of travel and the mid point.
Next you need to remove the rear seal, this is an aluminium plug. I drilled a hole in mine and used a sharp chisel to remove it.
Next a jig is required to mill out the remains of the rear seal housing with the router. Measure the opening of the casting in the damper body and make a plywood sheet that will support the base of the router. The plywood sheet will need the opening of the casting cutting out of it to allow you to mill out the seal casting.
As you can see the plywood sheet has the cut out slightly larger to accommodate the guide screwed to the router base. All wood routers will come with one of these attachments. Fortunately Mr Armstrong cast the damper body’s out of top quality aluminium so a standard carbide tipped router bit will easily remove the material. Don’t try to remove too much at once, just go gently. Also wear some safety glasses for protection against the shards of aluminium.
As you can see routing out the seal housing the router attachment follows the plywood jig, you just need to take a scratching off the bottom of the casting.
Next with some fine emery cloth and a flat piece of steel polish the casting to remove any machining marks, It has to be smooth but does not need to be perfect as the O Ring will take up any imperfections.
Next the damper arm needs to be removed and the front seal replaced. With the damper held in the vice, from the rear drive out the arm from the damper. Note where the reference marks made earlier lined up. I made sure the damper arm was at the 12 o`clock position with the marks lined up.
Next remove the steel shield and the failed seal and clean the housing.
The Oil seal required is 27mm dia, 17mm bore and 7 mm wide. It is a double lip seal. I purchased mine from my local bearing supplier at £3 each. Press in the seal and also smear a film of oil on the lips of the seal to help reinsertion of the damper arm.
Refit the steel cover, pressing it in with a socket.
With some fine emery cloth clean the surface of where the seal will sit on the damper arm.
Reinsert the damper arm, visually lining up the reference marks and press in the arm in the vice.
Next a plate needs to be made from 3mm thick aluminium plate to seal the rear of the damper.
As you can see I have drilled and countersunk 4 holes for M4*10 long c/sunk slotted machine screws.
Next a recess needs to be cut in the rear of the plate to house the O Ring to create the seal.
A jig needs to be made from a piece of wood to screw the plate to this will act as a guide for the holesaw. The holesaw is 20mm dia; remove the drill from the holesaw as it will follow the wooden guide to create the groove.
The dia of the O ring is 20mm dia and 18mm bore and is 2mm thick so the depth of the cut made with the hole saw is 1.5mm deep
Insert the O Ring in the cut out.
Mark out the holes in the damper body and drill and tap 4 holes M4 * 10mm deep. Note that the holes MUST be blind tapped as otherwise oil will creep up the threads and leak out undoing what we are trying to achieve.
Once again using some emery and a flat piece of steel remove any burrs made by drilling and tapping the holes. With the O Ring inserted in the groove screw the plate to the damper body.
Refill the damper with SAE 40 oil, moving the arm through its travel to remove any air trapped in the damper.
Refit the damper enjoy the ride!!!