6.9 strut overhaul - the story so far

[WGB]

My 6.9 has always had a weak right front strut although it never particularly leaked externally.

The struts are no longer procurable new but I purchased two kits of seals of US E-bay last year



The individual measurements of the o rings and teflon seals are given in this posting

http://forum.w116.org/mechanicals/as-rare-as-rocking-horse-poo/msg90765/#msg90765

The previous owner had also fitted wider than normal 140 Eight slot wheels and these had rubbed the right front hydraulic hose but have held up over the four years I have had the car.

In-situ with frayed hose - I have a new pair of hoses for the fronts.



Strut removed and sitting in the open air after a de-grease



Bottom ball joint removed with a 22mm slim spanner



Markings on this strut before being attacked with a pipe spanner



Top mounting clamped in vise and 18 inch pipe wrench attached to other cast end - unscrewed the top cover with some degree of difficulty



Here is a picture of the top cast cover still in the vise and showing the O ring in that cover



The next bit was the difficult bit strut reversed and bottom cast end clamped in vise ( with the piston removed through the top) using the bleed take-off point as a method of preventing it turning and after an hour of heaving with the pipe wrench I had only succeeded to turn the tube about 1 turn and then it was jammed even tighter and would not tighten or untighten.

Penetrating oil (probably irrelevant)  - left overnight - and another 30 minutes heaving later not one skerrick of movement. At the point of "repair-despair" I remembered I had a 6 foot length of galvanised steel pipe which I placed over the end of the pipe wrench and with about 5 to 6 foot of leverage and my not insubstantial weight it started to give with a lot of graunches and moans.

They appear to use something like red-loctite to prevent the cylinder from turning and probably as an extra sealant and it is very effective and the reason it is so hard to undo. Once the threads are cleaned of the stuff the cylinder can be spun into the housings very freely by hand.

Here is the bottom teflon seal tensioned by the thick O ring in the cast end with with the bump stop - this is after the bleed off point so it is really the "seal of last resort".



Here is the real shaft seal that is a push fit into the end of the cylinder and is held in place by the lower cap.



Here is a view of it from the lower side with a new seal and O ring fitted



Here is the piston complete with piston ring surrounding the valving.



Here is a collection of the bits laid out - the cylinder has been reversed and should be the other way around.



After a bit of overcomplicated stuffing around due to inexperience in the end the seal change is a walk in the park.

Lower cast end shaft seal (hat section teflon and fat o-ring) just pushes into the cast end by hand after removal of old seal



External O ring as well as old teflon seal and o-ring hidden under plain teflon seal are fished out with a small hook and replaced quite easily in the mainlower cylinder seal.



The new O ring is placed in the slot and then the teflon seal fed in over the top of it. The teflon seals against the shaft at the inner edge and the small o-ring on it's outer edge.



And of course a new O ring is placed in the upper cap



Here is a picture of the new parts waiting for "Cylinder rehabilitation" prior to assembly.



I am actually inclined to think that the poor performance of this strut has more to do with the glazing of the cylinder bore than the state of the seals . This picture shows the upper part of the bore which is quite matte in colour vs the very shiny lower bore.



Opinions on how I should deglaze the bore are gratefully accepted.

Bill

[TJ 450]

Excellent work.

I would just deglaze the bore with an fine abrasive pad, but there may be other suggestions like a cylinder hone perhaps. I think it will invariably need to be done due to the fact that the ring will need to re-seat itself.

How were the teflon seals looking? Do you think it is possible to get away with just replacing the o rings?

Tim

[WGB]

I think the lower hat section seal would have been fine with just a new O ring to compress it but the upper circular seal was sitting at a 45 degree angle and it would be near impossible to remove without damaging it.

It would need to be removed to replace the skinny little O ring that lurks beneath it.

Bill

[Big_Richard]

.

[s class]

That is fantastic Bill, thanks for the pictures.

My biggest fear would be distorting the central tube out-of-round when using the pipe wrench.  Do you think there was any risk of this?

I think you may be right about the glazing.  I would try scuffing it it with one of those green kitchen scourers.  I use those on brake caliper pistons and it leaves a nice smooth but dullish finish. 

[WGB]

Well 110kg of me on the end of 6 foot of pipe wrench doesn't seem to have distorted anything.

I think these struts are quite massively over engineered compared to any shock absorber I have ever seen and the tube seems to be quite thick and made of hardened steel.

I have a set of bore measuring calipers so will check the roundness of the bore but nothing visual to be seen.

Thanks to you and TJ for the pot scourer suggestion - I was going to use very fine emery like 1300 grade but am still awaiting any further suggestions.

Bill

[koan]

Opinions on how I should deglaze the bore are gratefully accepted.

Looking good WGB.

Think I'd be taking the cylinder along to hydraulic strut refurbisher to seek an opinion or have them do what's necessary.

If that's not practical a phone call may help with what to do, or more importantly what not to do.

koan

[TJ 450]

I'm pretty sure they rebuild hydraulic struts/rams at Westrac, South Guildford. I'm not sure that they would have time for anything other than CAT products, but could be worth a try for advice.

I'm sure there's plenty of independents out there too.

Tim

[nathan]

Great pictorial bill,
U have been on a rampage lately. Hope it pans out well. Do u knowif you can buy the top external boots?

[TJ 450]

Nathan,

Do you mean the rubber bump stop in the pics?

Tim

[WGB]

Hope it pans out well. Do u knowif you can buy the top external boots?

I have a full set of upper strut mounts courtesy of Tom Hansen if that is what you mean.

The back ones are in already as per a previous posting and the fronts will go in when I have finished with this strut.

I will then decide whether or not I will rebuild the left front strut but it is all a bit moreish.

I have also been taking advice from various engineers who have spent years re-building hydraulic rams and so far the opinion is a 60 degree cross hatch hone of the bore.

Hydraulics are standard fare in agricultural engineering just a bit strange for us petrol-heads.

I have two more to ring tomorrow.

Bill

[pal]

This is really helpful, thank you.