How to repair a damper

[Declan_Burns]

While discussing rear dampers recently with my colleague Hans Dieter Gollus, we decided to try and repair an old leaky rear damper that I had lying in my spares box. Looking at the price of the exchange dampers it is not really worth doing. But perhaps a day will come when no spares are available so we thought it would be good to know how to do it. It did cost us a damper in the learning process, but now we know the correct procedure. It's not really that difficult but access to a hydraulic press is a help. I'm sure that a simple bottle jack could also be manipulated. I sent the damper to Hans Dieter and this is the result:
First clean the damper thoroughly, drain it and remove the top six screws and cap. On the rear of the damper there is a plug. This plug is approx 1.7mm thick.and is firmly pressed in and must be sacrificed to gain access to the shaft. There is a 20mm seal behind the plug. It looks a bit butchered on the photo but could actually be removed cleanly using a milling bit in a pillar drill and subsequently levering the remains out with a screwdriver.
Mark the position of the damper arm relative to the damper body so that it goes back together on right splines. Use the press to drift out the shaft. The pistons can now be removed from the top of the damper. There is very little inside and no bearings to be replaced. The seal on the shaft measures 28x17x 6mm. Similar seals are used on electrical cable glands. This is a very primitive seal and we are trying to source a better one and are looking at lip seals.
Hans Dieter made a new plug 20.5 mm from aluminium and 20mm seals are readily available. The photos show the procedure how to take it apart and re-assemble. If we can get our hands on an old front damper we will do the same but I'm pretty sure the procedure is exactly the same.

Declan Burns
Hans Dieter Gollus[frame][/frame][frame][/frame][frame][/frame][frame][/frame][frame][/frame][frame][/frame][frame][/frame]

[millerman]

Very good description and photos

Presumably both seals are renewed?

[Declan_Burns]

Yes all the seals should be renewed. The photo just shows how it goes back together. We are sourcing seals and if we cannot find a standard seal, Hans Dieter can manufacture them as he has a plastics factory and has all the machinery. Infact we were just discussing manufacturing the elusive metalastic eyebolt bushes and possibly other items as we all know about the quality of repro parts.
Regards
Declan
Hans Dieter Gollus

[bmcecosse]

Excellent! Many thanks Declan. So - the shaft just runs directly in the body of the damper - no bushes or bearings there ?

[Declan_Burns]

Roy,
No bushes and no bearings.
Regards
Declan

[bmcecosse]

Thanks Declan - great exposé - now if you can just do a front one.....

[Declan_Burns]

If we could get our hands on one it wouldn't be a problem.
Regards
Declan

[bmcecosse]

What do you think the little 'plug' at the back does ?? Is it just to keep dirt out?? Would a washer and then a smear of silicon sealer do instead ??

[ian.mcdougall]

so if the hole in the body are worn it will still leak? can a bush be machined up to be fitted in the body as I would think the shaft is harder than the body so would not be worn

[bmcecosse]

This IS the problem with many dampers - particularly at the front - they wear and leak at the shaft. Maybe the fronts do have some form of renewable bearing there - since they are doubling up as dampers and top suspension link arm. I'm sure Declan will let us know soon!

[don58van]

Without wanting to detract from the helpful information information Declan and Hans Dieter have freely made available, I would add that Minor Monthly published a very good article on refurbishing dampers in the October 2007 edition.

Hopefully, these two information sources can be brought together to benefit all Moggie owners.

Cheers
Don

[Declan_Burns]

Don,
Do you by any chance have a copy of that article?

We will take a closer look at the body/shaft seal arrangement and post back. I would think the main problem is the seal. Hans Dieter is away on an engine building and maintenance course this week.
Regards
Declan

[Declan_Burns]

I've posted an ad in the wanted section on the German MMRD website for a front damper. Maybe sombody local will have one.
Regards
Declan

[bmcecosse]

I too would like to see the Minor Monthly article...... So if anyone has a copy and is willing to lend it - or scan and email - I would be very pleased!

[Declan_Burns]

Just sourced two front dampers from a kind MMRD fellow member and should have them mid January. (holiday period.)
We will do a similar write-up on receipt.
Regards
Declan+
Hans Dieter Gollus

[bmcecosse]

Well done

[Declan_Burns]

We picked up the front dampers yesterday afternoon.
Declan
Hans Dieter Gollus

[Declan_Burns]

Now we'll have a look at the front damper. This is a bit more difficult and certainly not a DIY home repair. Without the hydraulic press there's no hope especially when it comes to removing the arm which in our case was broken off anyway as some previous owner of the damper butchered it. Mark the position of the every part prior to removal to ensure it all goes back together as it was.
1) Damper viewed from rear



2) Milling the cap



3) Removing cap



4) Seal arrangement


5) Centre punching position



6) Presss out the shaft



7) Shaft removed


8 Front seal arrangement


9) Details on the inside



10) Oil lubrication grooves/keyway




11) Arm removed-it took more than 5 tons+heat to remove!


12) Valve details




Summary
It's very difficult to see if the bearing surface is machined or if in fact it is an insert. If this area is worn it would not be economical to try and repair although it can be done. If it is a case of just replacing oil seals then it is relatively easy as the arm does not have to be removed.
We hope you have as much enjoyment reading this as we had compiling it.

Regards
Declan +
Hans Dieter Gollus

[bmcecosse]

Well done! So - unless the damper is leaking oil - there really appear to be no serviceable parts inside. Is that the case ? And if it is leaking oil - it's likely that is because there will be some wear on the body where the shaft turns. Is that not a bush in there ? Does the shaft bear directly on the body of the damper ? Can you give us a clos-up of the little pistons - are they identical and is there any valving built into them ?? Do you think the 'cap' on the back does anything other than keep dirt out ? Could it be replaced with say a washer and some silicon sealer??

[Declan_Burns]

Roy,
Except for replacing the seals there are no serviceable part in there. The front bearing looks like a bush that has been pressed in, (we cannot be certain without distructive testing) and has two slots for lubrication. The rear end has no insert-it's the housing that has been machined but also has two slots for lubrication. On the rear dampers the housing has been machined and they have no slots at the front-just metal to metal-shaft to housing. The rear bearing has slots. The cap at the rear of the damper just compresses the thin seal against the collar in the housing and the seal has no contact with the actual shaft at all. This is the same on both front and rear dampers-so your idea of using a solid washer and some silicone might work-I don't see why not. That would imply that a damper that leaks at the rear is quite a simple fix. Removing the shaft is not so difficult -just leave the arm in place.We will try and source a lip seal for shaft of the front damper, we have one sourced for the rear damper already. The front damper front seal has the no. B29556 G37 6948/5 but no manufacturer mentioned. We measured it as 39x29x7mm which makes us wonder what the G37 stands for.
Replacing the front bush and inserting a new bush on the rear is possible but I think it would be a nightmare to set up the machinery. I would say that the places that recondition these dampers would just bin the housings if they show any signs of appreciable wear-it's simply not worth it as long as exchange dampers are readily available. One thing is for sure from this challenging exercise and that is all it was really, -the importance of keeping these dampers topped right up with the correct oil.

Front bearing[frame][/frame]


Close-up of the pistons-the pistons on the front and rear dampers are absolutely identical in size![frame][/frame]

Regards
Declan+
Hans Dieter Gollus