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Discussion Starter #1 (Edited)
Updated 11/2/11: after slogging away on this dream for 4 1/2 months in partnership with a BBer several continents removed this project has now come to successful conclusion:

http://www.alfabb.com/bb/forums/1068327-post43.html

4/29/2015: special CNC machined seal carriers are available again, please pm me if you want to place an order.

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Two recommended videos on the CDS system

Lancia Thema 8.32 (the original CDS)

Alfa 164 QV


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I recently took apart a 164S Sachs-Boge electronic strut (the solenoid was good but it was leaking at the top) and discovered that the "guts" are really quite straight forward (I will add pictures later). Seems that if the seals could be replaced and the strut refilled with the right oil and the right quantity, that the strut could be 100% restorable. There is no visible wear whatsoever on the shaft even though the strut has about 105K miles on it. Does anyone know of a source for oem metric strut seals? A search on the net turned up a discussion among BMW Z owners asking about rebuilding their adjustable struts and apparently a kit was available at one time, so my question about the "rebuildability" of the 164-S strut doesn't seem so far-fetched. Here's the pertinent quote from the BMW group (unfortunately that thread was never resolved) :

"the adjustable suspension struts on the z turbos can be rebuilt due to the fact that i read about the rebuild kits in a repair manual. The struts aren't gas but oil filled which  allows for the dampening adjustment. The only thing that causes a shock absorber or strut to wear out is the fact that the internal rubber seals are what go bad over time. I was just wondering if the kits could still be found, but thanks for your input."

Thanks!
 

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Would Also Be Interested In Knowing if these are Rebuildable

I recently took apart a 164S Sachs-Boge electronic strut (the solenoid was good but it was leaking at the top) and discovered that the "guts" are really quite straight forward (I will add pictures later). Seems that if the seals could be replaced and the strut refilled with the right oil and the right quantity, that the strut could be 100% restorable. There is no visible wear whatsoever on the shaft even though the strut has about 105K miles on it. Does anyone know of a source for oem metric strut seals? A search on the net turned up a discussion among BMW Z owners asking about rebuilding their adjustable struts and apparently a kit was available at one time, so my question about the "rebuildability" of the 164-S strut doesn't seem so far-fetched. Here's the pertinent quote from the BMW group (unfortunately that thread was never resolved) :

"the adjustable suspension struts on the z turbos can be rebuilt due to the fact that i read about the rebuild kits in a repair manual. The struts aren't gas but oil filled which  allows for the dampening adjustment. The only thing that causes a shock absorber or strut to wear out is the fact that the internal rubber seals are what go bad over time. I was just wondering if the kits could still be found, but thanks for your input."

Thanks!
Don't know if they are rebuildable, but I do have three adjustables from my 1995 Q that I would be interested in rebuilding/refurbishing.
 

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Discussion Starter #3 (Edited)
Thank you for seconding this, Tom.

Two interesting threads on strut rebuilding respectively from our BMW and MB brethren:

LAD strut rebuild

hydraulic strut rebuild - Benzworld.org - Mercedes-Benz Discussion Forum (scroll down to 5th & 6th post)

The first gives a very useful clue on the type of oil : pentosin. Okay that's a start, and to find the quantity, I can just measure in cc's what comes out of a good strut. The second gives a clue on o-rings and scrapers from "Tacoma Hydraulic" (a seal house).

The in the BMW thread the person writes: "started looking at rebuilding the struts mainly because of the exhorbitant price the dealer wanted for new ones". Hmm, that's a familiar note on this forum too. Come on Alfisti, let's solve this!
 

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I recently took apart a 164S Sachs-Boge electronic strut (the solenoid was good but it was leaking at the top) and discovered that the "guts" are really quite straight forward (I will add pictures later). Seems that if the seals could be replaced and the strut refilled with the right oil and the right quantity, that the strut could be 100% restorable. There is no visible wear whatsoever on the shaft even though the strut has about 105K miles on it. Does anyone know of a source for oem metric strut seals? A search on the net turned up a discussion among BMW Z owners asking about rebuilding their adjustable struts and apparently a kit was available at one time, so my question about the "rebuildability" of the 164-S strut doesn't seem so far-fetched. Here's the pertinent quote from the BMW group (unfortunately that thread was never resolved) :

"the adjustable suspension struts on the z turbos can be rebuilt due to the fact that i read about the rebuild kits in a repair manual. The struts aren't gas but oil filled which  allows for the dampening adjustment. The only thing that causes a shock absorber or strut to wear out is the fact that the internal rubber seals are what go bad over time. I was just wondering if the kits could still be found, but thanks for your input."

Thanks!
If it can be done that is good because they are all gone. I may have 1-4 various struts left but that's it. If I had the time I would tear one apart too.Good for you for looking into this.But there is always Koni if your decide it's not worth it and need struts. :)
Jason
 

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I'm looking into finding a rebuilder here (in PDX) - seems like there could be a cottage industry in this for someone.
 

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I've been told that someone here in Brisbane can rebuild them - I'll have to ask the guy who suggested it who it was, and what the charge is going to be...
I think the biggest issue is putting the gas charge back into them, but brazing a schrader valve fitting into the tube should be easy enough - the Bilstein guys do this all the time.
 

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Discussion Starter #7
... I think the biggest issue is putting the gas charge back into them, but brazing a schrader valve fitting into the tube should be easy enough - the Bilstein guys do this all the time.
Regular stock struts (164-B, 164-L) are indeed gas filled but not the Boge electronic struts in question here. Like Konis the Boge struts contain only hydraulic oil and are not under pressure. But please follow up on you Brisbane lead.
 

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I remember reading a few years ago that someone here in Melbourne (Oz) had his 164Q struts rebuilt by Benincas here in Melb. I think they did exactly as you mention above: replace oil & seals on his worn set.

Here's a link to their websites suspension info.

Haven't used their services for quite a few years myself but was always happy with their work back in the day...

Stu.
 

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Every koni shock I've dealt with had a gas charge, except for the old motorbike konis (ikon now)
So a brand new electronic strut doesn't slowly extend itself if you compress it?
I completely forgot to call about it today, will give him a call tomorrow.
 

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Discussion Starter #10
Arlyn Strano of Strano Performance writes:

"As to the oil verses nitrogen gas... all shocks have hydraulic oil. But, almost all shocks, save some Boges and Konis are nitrogen charged. The nitrogen keeps the oil from foaming and allows it to do the job".

Notice that he said "'save' some Boges and Konis". Which of course means some Konis and Boge have nitrogen and some do not. It seems pretty clear though that the nitrogen, if used, is to minimize the absorption of moisture (= anti-foaming), not for any recoil effect which some might contrue). That's where the use of the right oil for our Boge electronic struts is key, one that does not absorb moisture easily.
 

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It's not about moisture absorbtion - it's about oil foaming and cavitating. Anyway, I'm suprised that the Boges don't have a bladder or floating piston and a gas charge. Guess the answer is a set of remote reservoirs :D
 

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Discussion Starter #12 (Edited)
In looking at a detailed cutaway of the Boge electronic strut (from Alfa "Controlled Damping Suspension" manual, pp.129-130) I think you are right that the upper area between the outer tube and the inner tube is a gas cavity [REVISED]: (compressed ambient air but nitrogen might even be an improvement).



I've also found pertinent information on the Ducati motorcycle forum "Sach Boge Rear Shock Charge" and am optimistic that we will find a solution to this.

Here are some interesting comments:

"As long as you have the equipment it is a piece of cake compared to charging the AC on a Benz and a little more difficult than checking tire pressure." [that's comforting news]

Go to any competent dirt bike dealer or shop. Most racers and serious riders change their shock fluid every month. And when they do, it needs a new recharge of nitrogen. I've never seen a shock vary more than 10 pounds from the old standard of 140 pounds of nitrogen. The Nitrogen is only there to keep "air" from emulsifying (mixing) with the oil. It's NOT an air spring like the old Fox Shocks and such from the late '70s. If you loose your nitrogen, you probably need a shock rebuild. [this leads me to think that we can keep our struts performing like new with periodic rebuilding/recharging.]

"If your ride has degraded a little, you might just need a fluid change and recharge."
 

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Discussion Starter #14 (Edited)
I have pretty much come to the conclusion that the 164S electronic strut is fully rebuildable (I have found a detailed account of the successful rebuild of a similar Boge electronic strut for an M5 BMW). There are some possible exceptions. One of them is the condition of the shaft: if it shows visible wear, loss of the chrome plating, or pitting from rust that will foul the upper wiper seal you will waste your time. (Rust on the upper shaft area is usually caused by water infiltration due to a broken dust boot. A broken dust boot will also allow dust and grime to collect on the shaft leading to a shorter life of the uppermost seal causing the strut to leak). I am happy to share now some photos; it is interesting to note that certain internal parts of the Boge electronic strut are identical to the Boge standard strut (I have confirmed this as I have both types at my disposal):

exploded front strut (n.b.: the internals of the front and rear struts are the same—wiper seals, bushings, scrapers, o-rings—the only exception being the use of a longer piston/shaft for the rear, a different type of nut—screwing onto to outer threads of the casing, not inner—and the addition of a cap to protect the nut)





D E T A I L S (Boge dual-tube strut w/reserve oil chamber, from left to right):


▲ lower bi-directional valve + bushing (seldom needs replacing according the the experts)



▲ bump stop (on full extension of piston; no replacement necessary if in good condition)




▲ centering bushing (retainer for inner strut tube), band, internal nylon wear ring (not visible), large o-ring, and "double" seal (fits as an assembly ontop of the inner strut tube; critical here for leakage is large o-ring and double seal bonded to a bearing or washer; the gland nut cinches down on the outer edge of the bearing, squishing the large o-ring outward)




▲ top of strut casing showing interior strut tube (n.b. the bi-directional foot valve, affixed to the very bottom of the internal tube and not requiring any attention, is also employed on a standard Boge strut)




▲ top of shaft showing hollow end which I believe is where the strut is charged (or recharged) with air or nitrogen via a needle valve (see the little hole?) [Edit: False! This is optical illusion, shaft turns out to be solid]

Preliminary specs of the parts (from left to right) are:

- bi-directional piston valve/bushing (fits into interior tube): 32 mm OD x ca.9 mm H (probably does not need to be touched)
- bump stop: 29.5 mm OD x ca. 7.5 mm (height) (reusable if in good condition)
- upper "stopper"/bushing (fits into outer tube, directly ontop of the interior tube): 42 mm OD x ca. 11 mm (height)
(n.b. this part is interchangeable with a standard Boge strut!; this bushing band does not rub against any surface)
- small nylon rod bearing wear ring (inside of centering bushing): 24.3 mm OD, 22 mm ID, 2 mm height
- large o-ring 47.65 OD mm x 3 mm [Revised: just found standard off-the-shelf ring: 41.5 ID x 3mm @ $1.00 / o-ring]
- top bearing/"double" seal: 46.5 mm OD, 22 mm ID (this is a double seal bonded to a thick steel washer; on the lower
side it's a u-seal with spring girdle, on the top side it's a wiper seal keeping out dust) part no. 1-232-000-0279-2; also has
OOHSL 22-116
- piston shaft diameter: 22 mm
- 4-point castelated bronze male nut: 46 mm OD (needs a special gland nut wrench to remove without ruining)


My next step is to visit a hydraulic & seal shop to see how easily the double seal, o-ring and rod bearing wear ring can be sourced (the last two should be easy) and then, to talk to a motorcycle autocross shop that is experienced recharging struts with nitrogen. Interestingly, if my hunch is correct about the upper hollow shaft being the location of the refill, then periodic recharging the front struts on an Alfa 164S may be possible without removing the strut from the car. [Edit: I just confirmed the end of shaft is solid so no regassing here!] Loss of nitrogen after a few years of service is quite common (as mentioned in post #12 the gas guarantees constant pressure for the oil in the reserve chamber thus its loss has an adverse affect on the "soft" setting, not the "rigid"). It seems that a successful rebuild will only require the replacement of the nylon rod bearing wear ring, large o-ring and uppermost double seal molded to thick washerl. Stay tuned...
 

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As the owner of 2 cars with electronic Boge struts, I am also very interested in this. Looking forward to hearing if anyone has any luck with this. Unfortunately, the old struts from my Q4 were scrapped when I had them replaced.
 

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Discussion Starter #17
Welcome, Allan of Malmö.

I've just stumbled across a most interesting report from a person who worked on the development of the Boge EDC-System for the BMW M5 (the front strut of the M5 shares important attributes with our Alfa strut). He reports:

--front strut is the "two cylinder" type

--filled with a pressure of 4-5 bar

--gas used is normal ambient air ("normale Umluft") filled with a compresser

--air inserted at top scraper with needle value after oil is already in place

--working cylinder was filled full with hydraulic fluid with no air space

--the reserve area between the inner and outer cylinder should only be 2/3 full, the remaining 1/3 is for air (4-5 bar)

This report definitely speaks against the use of nitrogen (at least in the original product), although its use certainly shouldn't be ruled out, especially if its use will be an improvement.

The thread where I found this incredible report also make repeated reference to the air valve being difficult to remove, that it is often rusted in place, requiring drilling out, and a replacement valve
 

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Discussion Starter #18 (Edited)
Calling all S’s & Q’s.

I just hit upon a wonderful idea for this whole project. It’s one thing to rebuild the original Boge electronic strut for our exclusive aging fleet of S’s and Q’s, but quite another thing if we could scientifically verify our rebuild results by building a true baseline (and comparison vehicle) via dyno-tested statistics. Here is the plan I propose (open, please, to your comments):

I will provide information for a replacement upper piston seal and o-ring for the Boge strut and write up a step-by-step illustrated manual on how a rebuild is accomplished (a lot of reading has indicated to me that these are the only parts necessary for restoring strut performance, in conjunction with cleaning, re-oiling, and re-pressurizing). We are particularly fortunate—compared to other marks—that our front and rears struts use identical seals.

S and Q owners will be able to download this information free from the BB.

Owners can either DIY the rebuild, or take it to their local dealer.

Owners would then have their strut/s dyno analyzed on the Roehrig Strut Dyno. There are speedshops around the world that have this equipment and I do not believe the test and printout is expensive (example)

The results of each test would then be posted to the AlfaBB, gathered into one place under a single thread, or, assembled into one pdf file, viewable within that thread.

The model for this idea is the “Geektest” computer performance test where anyone can download shareware software to test their Mac computer’s speed, and upload the information to the Geektest website, providing a wonderful database of baseline tests, in context, that is, according to model, cpu speed, installed memory, video card, etc.

With the Roehrig dyno tune results the owner would provide (like the Geektest example) the basic parameters of his or her unit: country, year of car, model, front or rear, rigid & soft setting, approx. mileage, type/viscosity of oil used, quantity of oil measured in cc’s, any revalving if performed, amount of pressure charged, type of gas (ambient air, nitrogen). This way we will all be able to share, compare and analyze the results to see if someone has hit upon an optimal “recipe”, or basically, just to know if our strut falls within the general correct and safe parameters of an average baseline.

This seems to me to be the only way to truly rebuild, maintain, optimize and verfiy one of the most crucial components of our suspension system. We have a unique advantage here, as we would be comparing apples to apples (same dyno tester, one type of strut).

We must preserve our Boges, they are a beautifully engineered product—available on just a handful of exceptional cars—that need to be understood and maintained. Crazy idea?
 

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I am still interested and even though the rear struts are not the same on the Q4, I assume the structure and parts needed for rebuilding would be the same.
 
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