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Hydro-pneumatic system (HPS) restoration & install in a W123

Started by Greazzer, 25 April 2015, 10:21 AM

Greazzer

First and foremost, thanks to everyone who responded to my threads in the past few weeks on the precursor topics for this project.  Those responses helped me to make the decision to go forward with this mod for my W123, plus I am copy-katting all the others who have blazed a trail on the HPS system.  I am using the more uncommon W126 HPS system versus the W116.  The W126 is more in the weight class of a W123, although the systems appear virtually the same.  So, the information here is transferable to the W116 crowd.

I am soliciting folks to post as many pictures of their systems as possible, and hopefully the information I provide will help someone out in return.

Attached are some pictures.  Since the SLS pump is the same across so many model lines, and incredibly well documented, I will save that part towards the end.  I decided to tackle the rear struts first, since they appear to be  the easiest, the cheapest, and for some odd reason more available here and there on the net.

The rear strut appears pretty simple, part #126-320-25 13.  Sachs' part#: 06 2400 102 111 OD.

The rubber top bushing shows its age, part #116-327-14 81, which shares part # 126-327- 0281.  This part was first contemplated as being a mod'd or upgraded part, e.g., poly or some other material.  However, costs were not horrible, e.g., $67.20.

The bellows are toast.  Part #116-328-02 92.  Again, looking at universal bellows, but this one was surprising cheap at $26.80 for the MB original.

The hose, part # 126-997-40 82 is in surprising good shape, so that's a keeper.  It cleaned up good enough, and the inside bore looked about perfect.  Metric copper crush washers EZ Peezy.

The other pieces, e.g., tip, rubber bushing with insert, part# 116-327-15 81 likewise look amazingly well intact.  I guess being inside the cabin had something to do with that.

I will take some pictures of the strut tube disassembly.  The factory paint is still there, and the big white dot represents the orientation of the top (and bottom) piece.  The O-rings and nylon seals appear to be fungible, so just a few bucks.

The real zinger as for pricing are the ball joints.  I am looking at mod'g the struts to use rebuildable balljoints because there are a number out there which look just about the same.

Right now, my aggressive goal is to keep the entire project under $2,000.

Rear strut investment so far is $53.12 cores, + $8.50 shipping.  Bellows, rubber top bushing, seals, and ball joints will put me in the ballpark of around $180.00 per rear strut for a completely rebuilt unit (less the bits i am re-using).  If I go to new hydraulic lines, then they are around $20-ish at the hydraulic shop, so ballpark is $200 per rear strut.


TJ 450

Looking good... I'm sure you've found in your quest that a lot of these parts are no longer available, although for the most part these things are rebuildable.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

Greazzer

So far the only items NLA are the weirdo items, e.g., the stone guard (steel piece of tubing over tubing) from one of the front struts.  Not sure how in the world  that ended up missing, but it' gone.  One of  the arms off one of the cubes is missing, and I am betting that will be tough to find also.  However, all the other stuff is out there, original MB or one can use a subsitute.  For example, the cubes take a rubber dust boot and the dust boot from a sister Mercedes from the firewall fits about 98%.  I found a site which sells virtually every sort of dust boot and bellows, so I am positive I will match it up.  That is why I am shocked over the pricing of the bellows and upper rubber top bushing.  They were somewhat cheap so all of my research into mods or subsitutes was for nothing.  Sizing O-rings has presented its own challenge, but I will post all of measurements and specs since I only need "1" for each since I am guessing both sides for the front as well as rears are  the same.

Greazzer

Taking them apart required the strength of Hercules, so I had to cheat with a cheater bar but it still took all of my umph to get them part.  I copy katted the tread from WGB for the most part, although I found some tactics not working.

First, they needed to be situated in the vice only one way since they moved no matter what.  Here's a picture of how I held them in the vice.  You can see in the later pictures how if you're not careful, you can gouge the surface really bad.  I do not believe  this went deeper then the threads, so I should be OK.  Just stinks.  My virtually perfect painted surface is no more. :(

After the tops and bottoms came off, it was pretty easy after that.  It looks like 2 nylon bushings and 3 or 4 O-rings.  There was liberal locktite.

The piston parts do not appear to be rebuildable other than replacing  the O-rings and nylon inserts.  I suspect it will be impossible to find the "piston rings".  I do not understand the shim layout, but I zipped tied them so they did not come apart. I took pictures to  remember their orientation.  Even the top nut was staked in the corners which makes me think everything is torqued to specific values.  A Sach's factory shop manual would be helpful now.

When you remove  the casted metal top piece, you will see the 17mm staked nut and the first shim set which starts off with small to larger ones.  Again, not sure why that is so.

Then, you'll see a triangle type of washer.  Here's a picture which shows their sequence:  Nut, triangle washer, then shim set (1st).

Then, the top piston which consists of 2 types of rings (like an engine piston).

Then, the 2nd set of shims, in reverse order as the top ones.

Then, the inner ram.   I turned it counter-clockwise a bunch of times, although I do not think that had anything to do with it's removal.

Greazzer

You can see the 2nd shim set.  Reverse order as the 1st.  Again, no clue what or why these are in there.

The inner ram one had one sliding piece attached to it.

The aluminum ring off the ram has an O-ring and a nylon insert.  I suspect  this will be tackled latter since I cannot gouge these at all.

Here's a layout of the pieces.  Pretty straight foward overall.

and a close up of the inner piston (lower)

Currently, I am cleaning up what I got apart at this juncture.  I will try to figure out if there is a way to repair the main steel tube.  That was a dumb mistake.

Assuming the "piston rings" are fine, then rebuilding these things appears really simple overall.

Greazzer

Ordered all the parts and sorting out the O-rings and 2 nylon seals.  As for the rears, there are only 3 O-rings and 2 nylon seals.  The fronts apparently have 4 O-rings and 2 nylon seals.

Excluding the gouged metal, everything else came out well.  Even the balljoint is in good shape, really tight, et cet.  I cleaned it up, greased it, and will just re-boot it.

Here's a layout of the parts.  Overall, I suspect rear strut #2 should come out better.  So far, not an overly difficult job. The pieces screwed back together perfectly.

oversize

Wow well done!  Great to see you've documented your work!  I'd be very interested to know what non-MB boots will fit the control valves, rear struts and ball joints.  BTW I may have a spare control valve and regulator from a LHD 500SEL.  It's been outta action for some time so I can't guarantee it'll function correctly.
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

oversize

BTW when I have to rebuild my struts I'll be sure to use a set of vice soft jaws....
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

Greazzer

Thank you Sir !

If you have an extra main valve, please PM me.  Post some pictures if you want on this thread, or any pictures regarding the 4-corner HPS system, W126.

I think if I paid attention, I would have never gouged the tube.  Also, having taken one apart, I think my learning curve is already 50% or better.  I just zipped through ball joint removal, tip removal, et cet.  I just got the tube now with the 2 end pieces.  I am thinking the other ball joint is fine also.  It was incredibly nasty, and gunked up.  Just got done cleaning it and it's still nice and tight.  I think new grease and a new boot and I'm in business.

I am narrowing down the nylon pieces inside.  I believe they are called "L" scrape type seals made by Hercules.  It's actually a British design.  The O-rings are 70 durometer, which should be pretty easy for those.  Once I source the nylon inserts, it should be downhill from there.

I am hoping the front struts share the same nylon inserts.  I thought I found them over the weekend, but I was a little off base.

I know if I contacted Star Motors they will probably not disclose their info.  lol

The trick right now is getting the exact specs for the nylon seals and O-ring

Grane91

Quote from: Greazzer on 27 April 2015, 07:05 PMThank you Sir !

If you have an extra main valve, please PM me.  Post some pictures if you want on this thread, or any pictures regarding the 4-corner HPS system, W126.

I think if I paid attention, I would have never gouged the tube.  Also, having taken one apart, I think my learning curve is already 50% or better.  I just zipped through ball joint removal, tip removal, et cet.  I just got the tube now with the 2 end pieces.  I am thinking the other ball joint is fine also.  It was incredibly nasty, and gunked up.  Just got done cleaning it and it's still nice and tight.  I think new grease and a new boot and I'm in business.

I am narrowing down the nylon pieces inside.  I believe they are called "L" scrape type seals made by Hercules.  It's actually a British design.  The O-rings are 70 durometer, which should be pretty easy for those.  Once I source the nylon inserts, it should be downhill from there.

I am hoping the front struts share the same nylon inserts.  I thought I found them over the weekend, but I was a little off base.

I know if I contacted Star Motors they will probably not disclose their info.  lol

The trick right now is getting the exact specs for the nylon seals and O-ring

Hi! Did you ever went through with this project ?

rumb

'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

raueda1

Quote from: rumb on 02 April 2024, 08:42 AMhttps://forum.w116.org/shop/6-9-hydro-strut-rebuild-kits/

I have about 6 sets left.

Another member sells the front cups.
I can vouch for rumb's kit.  HERE is a detailed account of my experience.  I include it cause it touches on some issues not discussed elsewhere that I know of.  Good luck!
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0