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6.9 Hydraulic strut overhaul - take 2

Started by WGB, 21 January 2012, 02:14 AM

WGB

After posting the first overhaul of my RH strut I have now completed my LH strut as well and with the benefit of hindsight here are some tricks.

1) Gently heat the top cover to melt the loctite and the top cover comes off with almost no resistance - the heat needed is not even enough to blister the paint.

I was advised to use a chain type pipe wrench and after some difficulty I obtained one but as it really puts most of it's pressure on only one area I feel a normal stillson type pipe wrench is the preferred option as it grips on two sides and is less likely to deform the tube.



It is advisable to leave the old hydraulic hose in position while using the pipe wrench so that the seating face for the hose is not damaged by the pipe wrench.

2) the piston and rod is then pushed out the top and then the lower joint was heated - it really was only about four quick sweeps with the oxy torch - and again the paint was not even blistered.

The LH strut had a totally different design of piston to the right side with a piston ring and a more standard wrap around teflon seal as is often found in hydraulic cylinders.



The LH bore was in much better condition than the right with a much lesser degree of polishing and no score marks. I elected not to hone it but merely put it back together again.

The right hand side I gave a very light hone with small honing stones dipped in kerosene with two squirts of oil in a 200ml container - it ended up with a very light 60 degree cross hatch- and also on the RH side I removed the glazing on the piston ring with 400 emery on a sheet of glass.

3) the main seal is driven out of the cylinder with a length of plastic pipe and the teflon seal with hidden o-ring tensioner is removed and replaced and the outer O ring seal replaced





4) The lower teflon seal and O ring can then be replaced





5) The piston is pushed back into the bore from the lower end of the cylinder ( The bore is shaped to allow this to happen easily without a need for any ring compressor) and after a couple of turns with emery to smooth the bottom end of the shaft then the main seal is lubricated and pushed over the shaft and into the cylinder, Lastly the lower seal is lubricated and pushed onto the shaft

Here the main seal is seated in the cylinder with the the lower seal now coming up the shaft



And here is the same stage with the view reversed to show the lower seal being pushed up the shaft with the lower end of the main seal about to seal on the fat lower O ring and tension the lower teflon seal



6) At this stage I would deviate from what I actually did on both my struts by screwing a liberally loctited cylinder onto the bottom joint using a pipe wrench on the dry upper joint cover without 0 ring or loctite.



7) Then I would screw the top cover back on with a new O ring and lots of loctite.



As you can see - the upper cover seals on the outside of the cylinder via it's O ring and does not need to be turned up tight to make a seal and the loctite will prevent it from turning.



The reason for doing this is that if the two are tightened together and left that way the upper hose and bleed pipe are out of alignment ( as both of mine now are)

Here is a picture of my original right strut before removal



And here is a picture after replacement showing the misalignment - there seems to be plenty of length in the tube and it is no big deal but you might as well learn from my mistakes.



7) The strut is now refreshed externally - tool marks removed and re-painted.



Here are some views of the old top mount and the new showing the depth of compression





8) The new top mount is bolted up and the angle is critical - if the hose is rotated too far to the centreline the hose may foul on the mount when the strut compresses in future years and too far out and the hydraulic hose may rub on the tyre.



9) Bottom stone-shield is replaced and the lower ball joint is tightened using a thin 22 mm spanner while holding the stone shield.

The reason the stone shield holds the strut is that it's lower edge is double skinned with the inner skin having the shape of the lower part of the strut and thus acting as a spanner.



The strut is now replaced with a new hose and copper seal.

This picture of the LH side shows the position of the LH bleed tube but by the time I had worked it all out the loctite had set and it was too hard to go back.



I then replaced the wheels and started the car but try as I might the low pressure light would not go out so I decided to bleed the pump and it was while taking this photo demonstrating  the pump being bled I noticed my disc was still in the "M" position (DUHH!!!).



With the disc in the correct position the car pumped up immediately.

The reservoir was quite low so I put in my last remaining bottle of Hydraulic fluid and went for a 10 minute drive  to Mundaring Weir.

The ride was significantly better with the new mounts and even better the car has stayed pumped up and not lost 1mm ( I have been measuring it each day while finding time to refit the rear seat) of height over the past three days.



It has taken another 1 1/2 bottles of hydraulic oil to bring it up to the correct mark - not sure where it all went as it didn't seem to lose that amount.

I am looking forward to a longer drive and getting all the air out of the system.

Bill










pal

Thanks Bill, for a second I was looking for a 'like' button - cheers  ;D

KenM

You're a machine Bill, just shows what can be achieved with some planning and forethought prior to attacking any job, congratulations on a very professional job and thanks for posting.

TJ 450

Excellent news,

It's very interesting to see the difference between the struts. I wonder if it is an updated version or something along those lines?

Or, have you checked the part numbers?

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

mirafioriman

Great write up and practise makes perfect as they say ;)

Can you remind us again where the seal kits came from? Was it ebay?
I'm called Dave! I currently own: Mercedes W116 450 SEL 6.9, Mercedes W109 300 SEL 6.3, Mercedes W126 420 SEL, Fiat 130 Berlina, Fiat 131 Supermirafiori, Fiat 131 Panorama, Fiat 132 2000, Fiat Argenta and a Citroen Xantia.

WGB

Hi TJ - both struts had the correct part numbers on them for standard struts on their correct sides.

Mirafioriman - yes an act of faith on eBay and the kits were not cheap at $200 per side . The original post is entitled " As rare as rocking horse poo"

Bill

mirafioriman

I'm called Dave! I currently own: Mercedes W116 450 SEL 6.9, Mercedes W109 300 SEL 6.3, Mercedes W126 420 SEL, Fiat 130 Berlina, Fiat 131 Supermirafiori, Fiat 131 Panorama, Fiat 132 2000, Fiat Argenta and a Citroen Xantia.

koan

Great work and pictures again Bill.

koan
Boogity, Boogity, Boogity, Amen!


oversize

Ok so how do we 'rebuild' these suckers??  I've heard it's possible and that they're very expensive new...



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

TJ 450

Hi Mark,

You could ask that person on that other forum, or rinse it out with solvents and evaluate yourself. 8)

All I did on the 560 was rinse them, grease and fit generic boots. Not like new, but they are certainly going to last longer than with no boots and dirt contamination amongst other things.

Huge amounts of play might be an issue.

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

oversize

I'd like to rebuild them here, rather than send them all over the country!  What boots did you use (from which car)?  I wonder if it'd be wise to add a grease point?  I assume graphite grease would be the best?
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

I read somewhere in the MB manuals that if the boot is damaged the ball joint should be replaced as a matter of good practise (and a precaution)....  I guess that was when parts were readily available (which I believe the front ball joints are not) and the costs were a little more reasonable.  Here's a costing I did about a year ago from an Aussie dealer ($AUS):

1163271881 front strut upper mounts $406.95ea,
1163271481 rear strut upper mounts $231.41ea,
1163201028 rear strut ball joint $2031.77ea,
1263201315 rear cell $1188.74ea,
1263200715 front & central cells $735.49ea,
1163280292 rear strut boots $90.52ea.

I think molly grease should be suitable!!   :o :o
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

robertd

Hey Bill,
Very informative post, good to see the clear and precise step by step instructions.
Rob
116   1978 450SEL 6.9 #  4848
116   1979 450SEL  6.9 # 5884
116   1979 450SEL  6.9 # 6225  SOLD
116   1978 450SEL  6.9 # 5128  SOLD
116   1979 450SEL  6.9 # 5884  SOLD
116   1974 450SEL  DJet

WGB

In hindsight the most important part is to lightly heat the joints with the piston at the opposite end to break the seal of the locktite used in the original assembly process.

The second point is that the top cover does not seal down tight on it's thread (as I did - the seal is actually the o-ring) but left in the correct position to align bleed tube at the bottom and pressure pipe at the top and using the red loctite to effect the locking effect.

Bill