Home Rear Damper Repair

Rebuilding, adjusting, maintaining & alternatives

Home Rear Damper Repair

Postby Rick1963 » Tue Nov 19, 2013 11:53 am

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.

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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.

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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.

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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.

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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.

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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.

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Next remove the steel shield and the failed seal and clean the housing.

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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.

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Refit the steel cover, pressing it in with a socket.

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With some fine emery cloth clean the surface of where the seal will sit on the damper arm.

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Reinsert the damper arm, visually lining up the reference marks and press in the arm in the vice.

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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.

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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.

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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

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Insert the O Ring in the cut out.

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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.

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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.

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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!!!
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Postby MM » Tue Nov 19, 2013 12:16 pm

Interesting technique - thanks for posting.

I guess the rear seal is 'belt and braces' stuff, because once you've bolted the damper to the fixing bracket, it would effectively seal itself anyway.
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Postby Rick1963 » Tue Nov 19, 2013 2:57 pm

The rear seal is required as oil seeps from the rear due to wear from the shaft.
One of my aims of this project was to show that with a few tools and a little application the damper can be successfully repaired at home. At some point 2nd hand ones may dry up as parts like this become scarce.
After thinking and reading about dampers I have come to the conclusion that the reason they fail is because the seals fail, they then run dry. The damper oil also serves as lubrication for the various bearing surfaces inside it, without lubrication the damper wears the bearing surfaces oval due to the amount of travel of the link arms and the geometry of the suspension. Either keeping them topped up or replacing the seals are the only options.
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Postby woodywoodchipper » Tue Nov 19, 2013 5:08 pm

well done,

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Postby TeHoro » Tue Nov 19, 2013 6:18 pm

Hi Rick

Thanks for the clear explanation and write-up. It looks like a good solution to a leaking damper seal.
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Postby ruairidh » Tue Nov 19, 2013 6:41 pm

Very interesting. :goodpost:
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Postby austin » Fri Nov 22, 2013 8:33 am

Of course in the days of the Morris Minor, 1950's and 60's, we never called them dampers. It was a shock absorber.
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Postby MM » Fri Nov 22, 2013 11:55 am

Techically, the spring is the actual shock absorber, i.e., the bit that takes the shock and reacts to it.

The damper is a device used to smoothen out the resulting rebound oscillation.
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Postby woodywoodchipper » Sat Nov 23, 2013 4:46 pm

Question,

apart from the splines is there anything else that locks the shaft in place,

I ask as in the pictures there is nothing shown, and what can stop the shaft just coming out on its own, :?:

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Postby Rick1963 » Sat Nov 23, 2013 6:23 pm

Hi Woody,
The shaft on the splines are such a good fit so there is no other method holding the shaft in place.
If you were repairing the damper in a workshop then no doubt you would use a press. As you can see in the pictures the end of the shaft does suffer some damage from using a punch to remove the arm.
When I was removing the arm from the damper I started by using a brass punch, this soon bent with the amount of force needed, plus I have a bruised finger too boot   :D
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Postby woodywoodchipper » Sat Nov 23, 2013 9:46 pm

:wink:

cheers,

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Re: Home Rear Damper Repair

Postby Rick1963 » Sat Mar 01, 2014 6:14 pm

Well, it's been 4 months from when I repaired my rear dampers, since then I have done short trips locally and last week a trip over the Pennines to the Manchester Bus Museum. I can report that the dampers and the seals are still sound with no oil leaks from the front or back of the damper. The SAE40 oil improves the damping no end and as a result of the repair and the oil, the ride is much improved.
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Re: Home Rear Damper Repair

Postby bmcecosse » Sat Mar 01, 2014 7:24 pm

Indeed it will be - well done !
 









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Re: Home Rear Damper Repair

Postby Dave1951 » Sat May 28, 2016 7:14 pm

excellent post and extremely useful. I may be attempting this repair soon as my right rear damper has started weeping.
much appreciate all the info and experience that is so willingly shared
All the best
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Re: Home Rear Damper Repair

Postby bmcecosse » Sun May 29, 2016 10:13 pm

From what I have seen of Minors with the crappy bolt-on tele-damper 'conversion' - lever arms filled with SAE 40 are FAR superior. There is sufficient travel on the lever arms to allow removal of 1" from the tips of the rear bump stops, and 0.5" from the fronts - which greatly improves suspension travel too before it rattles your eyeballs. Well worth doing!
 









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