The writer’s S2 Elan ownership extends for nigh on forty three years, definitely long term, and time enough to become familiar with many foibles of the lotus elan.
The passion for Lotus runs deep, as you might suspect when you take the long term ownership into consideration.
Over the past several decades there would be very few components of the S2 elan that have not been dismantled and rebuilt… twice over in some instances, and most pull downs have been to the last split pin and washer.
But having said that, I have come to realize that there are two important items that have never been serviced, and those two items happen to be the rear Koni strut inserts.
… Hidden away and almost forgotten.
We can all adhere to the old motto, “If it ain’t broke, don’t fix it”, but in reality, how can you tell what’s going on inside of something if you never bother to take a look?
These over worked and often neglected items just seem to keep on keeping on, but as time progresses, the performance can fall off unnoticed unless the shocks are removed and tested on a shock Dyno, or the suspension simply becomes so soft and slushy that you are forced to do something about it.
In the writers case, the shocks were not up to the job, and it was probably more good luck than good fortune that the elan S2 was fitted with Koni Special D Sport (82T-1835) 611 Sport, which are the fully rebuildable type of hydraulic fluid filled shock or damper.
The initial plan was to remove the shocks from the car and send them off to the Koni rebuild agent located more than three hours away, but upon inquiry, we were informed that the rebuild work was backed up for a minimum of one month!
... A time frame that I simply could not afford.
So after some thought, we decided to remove and pull the Koni strut inserts apart in our own workshop to see what was going on inside, and to see whether it was possible to do a DIY rebuild, after all, they are just a simple twin tube hydraulic unit with a couple of fluid control valves inside…
The dismantle job cant be that difficult to do?
As with most car owners when it comes to the servicing of shocks, it seems to be an area that is generally avoided by the DIY home mechanic. And also considered by many to be a black art area … in other words … not to be messed with.
And you should note of course, if the shocks fitted to your car are of the NONE rebuildable type, or the shocks are gas filled, then the DIY rebuild story stops right here for you…
And probably time to consult the expert! Or Maybe It’s Time to Purchase A Pair Of New Shocks
Well, as I said, the ones we are dealing with here were the good old fluid filled Koni special D’s, and with me being of the adventurous mechanical type, I am willing to explore when it comes to mechanical things.
So lets get into this project.
The rear of the elan was raised with the hydraulic race jack and placed onto floor stands in order to begin the job of removing the rear struts which is not really a big job if things are set up for it, and as you’ll note, the car is parked over a floor pit, making it much easier to work around and under the car. It would be nice to have a two post hoist, but we don’t.
You don’t miss what you haven’t got.
Removal of the rear strut assembly is a relatively easy job. The strut illustrated above is a modified unit – narrow wound springs, topped with a small diameter alloy spring cap, coil springs sit on adjustable threaded perches, the narrow springs and alloy cap allow access to the retaining socket head cap screws that secure the loto-cone to the top rear chassis tower bracket. (Access to the studs would not be possible with standard springs).
The rear brake caliper is removed from the strut without breaking the lines and simply hung on a strong wire hook that is looped over the top loto-cone chassis mounting bracket.
A special long reach hex 1/4″ driver tool was made up and employed to unscrew the socket head cap screws to release the strut … of course the CV drive shafts are removed prior, and the outer bolts of the Lower A arms are also removed, the A arms are then allowed to droop to allow the work to progress.
Remember to also release the hand brake actuation rods from the calipers.
With some careful manoeuvring of the jack, the complete strut is carefully lowered and removed from the car – yes, I know, this is quite different to what the lotus workshop manual describes – I personally do not like that particular method, so we adopted our own method many many years ago.
The loto-cone bolts have been removed, strut assembly is now ready to lower it down on the jack.
Strut assembly is now fully removed from the car, this method is far easier than what the factory manual suggests, this is a one man operation. The brake caliper remains connected to the lines and hangs on the temp support hook until re-installation of the strut assembly.
While working on the struts it was discovered that a radial crack had propagated on the alloy bearing housing, the crack seemed to be following the circlip or snap ring path, so a pull down of the axle hub was required to carry out a welding repair.
The trusty wheel hub puller which we fabricated decades ago was called back into action. This is a safe and reliable way to remove the wheel hub flange for bolt on wheels, the puller is mounted as shown and a large amount of preload is applied with the UNF threaded centre bolt, then the oxy torch is fired up and heat is carefully applied to the boss part of the hub.
The amount of heat applied is just a little above what you could stand by hand touch, then the torch is put aside, and a heavy hammer is used to whack (Impact) on the head of the heavy HT bolt, after about three or four impacts, the hub will be heard to “pop” and that will be the hub taper releasing … remove the puller tool to gain access to the hub flange and the key way, put then aside for later. (A Porta-Power Could Also Be Used- but be careful)
The rear axle is probably one of the most difficult pull apart jobs on the elan.
Because of the design and configuration of the strut, it is not easy to place into a garage press in order to press the axle out. The best tool for the job is a screw on impact tool and special shoulder impact collar.
The thrust collar is placed over the threaded axle spigot, and abuts to the machined shoulder on the end of the axle, the impact tool has an internal matching axle thread, simply screw it on to the axle and nip it up tight onto the collar and axle shoulder.
The large circlip that retains the inner bearing (next to the disc rotor) MUST be removed prior to any work being carried out, this circlip can be a sod to remove, so work carefully and patiently with the correct tools.
When impacting with a hammer on the head of the screw on impact tool, the force is transferred into the axle via the impact collar, there is no damage being done to the thread or axle end as long as the tool is kept nipped up tight.
Before the impacting begins, the alloy bearing housings need to pre-warmed, we use an Oxy torch to preheat a little above what you can stand by touch, THEN the impacting can begin, the axle should begin to move, but you may need to apply a bit more heat if required … it is a trial and error process.
Once the bearing has popped out, it will look like the photo above. Unscrew the impact tool. Now it might be possible to place the strut assembly onto a garage press to remove the axle and disc rotor proper from the housing… OR, use a piece of hard wood and hammer, to work the axle out of the outer bearing. As previously mentioned, it can be a sod of job, but doable as a DIY job if you have the tools.
Now that the strut housing has been dismantled, the welding repair can be made to the alloy housing. The crack is not a huge drama. These struts are now fifty nine year old items, they are not going to last forever.
The small radial crack was prepared for welding using a die grinder and a small round burr to create fillet depth and penetration for the TIG welding. The repair was farmed out to a local TIG welding specialist we use for this type of repair. Photo shows the quality welding repair carried out, and will help to prolong the life of the housing for several more years.
With the penetration of the TIG welding during the repair, the inside of the circlip groove became uneven due to weld penetration which meant that the circlip would not seat and engage correctly into the groove.
The only way to correct the problem was to set the housing up in the vertical milling machine and re-cut or clean the groove. This required a special boring bar was made with a slot cutter the width of the circlip groove so that it could be mounted in the indexable Mill boring head as shown below.
In all truth, once the work piece was set up, the machining operation was carried out very carefully by turning the quill of the mill by hand to slowly rotate the boring bar which re-cut the circlip groove. The operation was a success.
If the housing suffers another crack in the future, it will be replaced with a new item.
A milling machine is a must have for the serious home workshop machinist, photo above shows the simple jigging-holding fixtures for the lotus elan rear housing.
Now Lets Get To The Real Reason For This Long Article – Koni Rear Shock Dismantle-Rebuild.
You really never know what you are going to find when you begin working on your classic car – A simple job can escalate into something far more involved – The trick is to not let it beat you – And to have the skills and workshop gear to do the repair/rebuild your self.
OK, this is what we started out to explain to you at the beginning.
The dismantling and re-assembly of a pair of Koni Twin Tube Special D oil filled sport shocks.
Note that the shock above is sandwiched and held securely between hinged wooden blocks, the blocks were set up in an older lathe (Four jaw chuck) and bored out to suit the Koni outer housing OD, this is a secure and safe method to hold the shock in the vice with out damaging or squashing the outer housing tube.
Now you’ll realize the advantage of the wooden holding block, with the assembly clamped firmly in the bench vice, considerable force can be exerted onto the edge of the gland nut to unpick the swage formed on the top edge of the outer shock housing. There are only two swages on the shock, and they are opposite each other.
A stout screw driver and a small nail punch was used to flare the metal outwards. Don’t worry if it looks a bit untidy, the outer housing can be fixed up a later on before re-assembly.
With a bit of leveraging work, the swage is soon undone, now the innards of the Koni shock can be revealed.
After unpicking the swage, I could not believe how black the old hydraulic fluid was, and it had a bit of a smell about. It is important not to spill any of the oil in the shock as the amount of oil in each shock must be poured into a measuring container, so that you will know exactly how much new oil to replace during the rebuild. You wont find any of these kind of useful details on the Koni info web site, nor will they reveal what type of fluid to use when re-filling the shocks.
This is what happens when shocks are neglected, the oil wears out, loses its viscosity, and the shocks don’t work as well as they should.
You need to know how much oil each shock requires – it is very important to measure accurately.
The various parts of the Koni Shock – Not that complex really – and to my surprise the wear between the various parts was not excessive. Each part was thoroughly cleaned and blown off with compressed air, then inspected for damage and other possible problems – All seemed to be pretty good.
This is probably where the true science of shock absorbers lie – in the special valves that are used to control rebound and bump, early konis have to be removed from the car to adjust, but the latest types have external adjustable screws or knobs for bump and rebound control.
DO NOT use a steel engineers hammer when removing the burrs and buckles from metal, a steel hammer will expand and stretch the metal and make the OD of the tube incorrect.
Always use a hardwood or hard nylon hammer with the outer tube placed over a steel pipe section as the anvil.
There are special peg tools available to dismantle the gland nut, but it seems that others before me have elected to use other tools to assemble and remove the Koni shocks – The next job here is to pull the gland nut apart.
The first step in dis-mantling the gland nut – you will be surprised at what is inside – The threaded ring retains the seal pack, the lip seal acts as the wiper on the shaft.
A mechanics gland seal picking tool is a a very handy item when doing this job, otherwise damage could be done to the seals.
Hard to believe that so many pieces of the seal pack are retained in the gland nut. Every seal piece was removed, carefully cleaned and noting the correct order of the gland pack assembly – In reality the gland pack should have been replaced, but surprisingly, every piece was in very good condition.
The outer housing of the Koni shock had a coat of old black paint that required sanding off, so the outer housing was mounted between centres in the old lathe, and sanded while it was rotating, it did not take long to remove the old paint. Priming and painting was left until last.
The Koni is now ready to re-assemble, all of the parts have been cleaned and inspected for any undue wear. The rebound valve on the end of the strut rod (Above) was turned back to the softest setting, and flushed out with de-greaser, then blown off with compressed air – It all looked good in that department.
In the past, the car had been run without the Aeon bump stops, (BIG Mistake) the big fear was that the bottom valve might have been damaged, requiring replacement, but that wasn’t the case, both valves were in A1 condition. (Very lucky indeed).
There was one fault discovered with the Koni’s.
The control valve located in the bottom end of the inner tube was very loose which prevented the ability to adjust the damping rate of the shock. The valve is supposed to be a light press fit into the end of the inner tube and the feet rest under light pressure against the bottom of the shock housing.
The only way to recreate a press fit, was to centre spot punch onto the shoulder of the valve at 120deg, the valve was then a firm press fit and remained in the tube during assembly.
This is where the split wooden holding block comes in real handy. Mounted in a drill vice it makes the perfect holding base to enable the first part of the shock re-assembly to begin.
The first item to go into the housing will be the inner tube, just slide it in until the valve rests on the bottom of the outer housing tube, the inner tube also has an external sheet metal ring that helps to centre the tube in the housing.
After the centre tube is installed, the strut rod can be lowered into the inner tube. The adjustable valve at the bottom of the rod is a neat sliding fit into the tube, smear some damper fluid onto the rod valve to lubricate the surfaces to aid installation.
Once that is done, the new fluid which for these shocks was measured as 200mm … and NO More, is poured in bit by bit.
As the fluid is carefully poured in, the strut rod is moved up and down to draw the fluid into the working parts of the shock, a lot of air is expelled and it will gurgle and pop as the rod is worked up and down several times.
Refill Fluid: Renolin B HVI Plus 46. Has worked extremely well in the rear koni shocks. Others have used ATF Automatic Transmission Fluid, and that is OK. Special fork oil can bought – is it any better than what we have described above, probably not. (But someone may take me to task over that)
When bleeding, the resistance will be felt and it gets a bit tiresome, but it has to be done.
When all of the fluid has been poured into the shock, the top guide bush (Which locates under the threaded gland nut) can be inserted into the tube, followed by a new O ring, followed by the gland nut, which will need to be pushed down over the strut rod, the gland packing can be made loose when fitting , and then tightened up a bit later.
During the pull down and rebuild, advice was sought from various people through various channels, but for some reason, it was difficult to find someone who was willing to give advice, the comments were, “We don’t normally do that, send the shocks to us and we will rebuild them”??
The local bearing shop was able to match the “O” rings, the shock fluid refill was Fuchs and is visible in the preceding photograph.
But we were not one hundred percent sure that choice was correct but the fluid does work extremely well.
A search on google presented many differing advice scenarios, so in the end we stuck with what we had and that was the Fuchs fluid, which as it has turned out was a good choice because the shocks are working very well indeed, a big improvement on what they were like previously.
(Footnote: with the next pull down, ATF fluid will be used as shock fluid.)
The damping adjustment on the Koni special D from full soft to full hard is 2.2 turns of the strut rod, and because of the age of the shocks plus the stronger springs (80LBS) on the rear, we set the damping at about one turn towards hard, and that seems to feel about right.
It would have been nice to place the shocks in a shock Dyno to set the damping rate to match the 80lb springs, but not having anything available locally, that was not an option, BUT, I also realize that if a Koni workshop had carried out the reco work, a dyno test could have been done at the time of the rebuild, and would have saved the trial and error of different settings.
That’s a choice I made, and I don’t think I was too far off the mark with the damping rate.
When inserting the upper guide bearing bush and the gland nut in readiness for swaging of the outer housing, a small amount of pressure must be exerted on the gland and inner tube assembly.
The simplest way to do this is to mount the shock body vertically in a workshop press where, with some special tools, a small amount of pressure can be applied so that when the hand swage is being done the preload will be retained on the “O” ring afterwards affecting a proper seal so that no fluid will escape. (For some reason we omitted to take some pics of that work)
The rear struts, assembled complete with the new machined alloy bump limit cones, as well as the absolutely necessary Aeon Rubber bump stops – Many people are now calling these items progressive rubber springs, and I tend to agree.
The Lotus elan shoulder NEVER be driven on the road without the Aeon rubber bump stops installed on the rear struts. If your car does not have them, go out and buy a pair today and install them, you will be amazed at the difference in the way your elan will ride and handle.
All of the above work took about three or four days to complete. We are now confident that everything is right with the rear suspension set up, the short test drives since the reco work was completed indicates that the work has been very worthwhile.
I know you may think that this is beyond your skills and workshop facilities and you would rather send them out, and that’s fine. But I know there will be others out there who may happen to learn something from this article, and that is all we want to achieve, to help other elan owners to carry out maintenance and servicing on their own cars, or to help owners to understand more about the car they drive.
The next project on the list is to pull the front Konis out and over haul them, and also to install some new and correct Koni bump stops, as you can see, I am mad about having the correct bump stops.
Watch this space.
Note: Front Konis Have Also Been Rebuilt.
What a huge difference all of the work carried out on the front and rear shocks and suspension has made. The S2 elan now swallows up the bumps and bad road undulations without fuss or bother, a superior car to drive, and also to ride in. (Grin)