Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 4/4 Sigma 2014, problems with the steering -solved

Yes Heinz. The difference is small, but is also noticeable. The plunger was locked solid, and took "persuasion" to release, so it was allowing a tiny amount of vertical rack movement, which led to the tiny amount of play at the wheel. I guess that's the best indicator. So far my 2016 has zero play at the wheel, but obviously at some point will need attention.

The thing is that few owners have the experience to do this. I wonder how many dealers have done this job because until you raised it here I had never heard of this as an issue.

Sewin: I use my vice/drill "lathe" for all sorts of "refinishing". The irony is that my son in law has a real lathe in his shed, but it's just too far away for a quick job, unless it was vital. The alloy spacer which fits under my spare wheel T bar comes up a treat when drill-lathed with wetndry!

Just adding a bit more, "Nylon" absorbs water. This is from the Amco Polymers website:

This is a peculiar effect given the the steering rack pressure pad is enclosed and greased. Apparently Nylon can be dried, so in theory the component could be removed and dried out in a warm environment, where it would presumably return to its original size. The good news is that once "saturated" it does not take on more water. However it does confirm that swelling of the pad will be time related but also atmosphere related. In dry climates it should not be a problem.

QUOTE:

Nylon resins absorb moisture from the air. The properties of nylon moldings are directly affected by the amount of moisture they contain. Moisture acts as a plasticizer in nylon and therefore reduces strength and stiffness properties but increases elongation and toughness. In general, as moisture content rises, significant increases occur in impact strength and other energy absorbing characteristics of the material.

Why Do Polyamides Absorb Moisture?
Nylons, having a ‘polar’ structure attract moisture. The amount of moisture absorbed depends on several factors. The temperature and relative humidity, the exposure time, the type of nylon and the part thickness, all influence the moisture absorption characteristics for a given nylon. In general, a nylon part that has a higher crystallinity will absorb less moisture than the same part that was molded with less crystallinity.

In hydrogen bonding the hydrogen atom on one polymer chain wants to bond to an oxygen atom on another polymer chain. This hydrogen bonding is one of the reasons that nylons have good thermal and mechanical properties.

Moisture absorbed into nylon also wants to hydrogen bond. The hydrogen atom in the water bonds to an oxygen atom in the nylon polymer chain. At the same time, the oxygen atom in the water bonds to the hydrogen atom in the nylon polymer chain. This hydrogen bonded water molecule acts like a plasticizer, allowing the nylon polymer chains to slide easily along one another. This is why nylon drools and flashes if it is injection molded wet. Moisture absorbed onto the surface of the nylon resin or part can generally be removed by drying for 3 or 4 hours. However, for moisture that has absorbed more deeply, a much longer drying time is needed, sometimes up to 24 hours or more. In order for this moisture to be removed it is necessary to not only break the hydrogen bonds but to allow sufficient time for the water molecules to diffuse to the surface.

Effects of Moisture Absorption on Properties
The water molecules that hydrogen bond between the nylon polymer chains cause the to move farther apart from each other. This causes a ‘loosening’ of the molecular attraction which causes a reduction in mechanical properties and an increase in fluidity. The glass transition temperature reduces, and can drop by 20°C or more. The strength and stiffness decrease while the impact and toughness increase. The amount of reduction in mechanical properties is dependent on the amount of moisture absorbed.

Just gave my steering wheel a wiggle and no detectable play at all. That's after 52k miles and 13 years.

Certainly true of rudder pintle bearings on a sailing yacht I once owned. The nylon had expanded in seawater and picked up on the lower stainless pintle, splitting bearing. A Delrin replacement was turned up. This material is still not perfect in avoiding water absorption but far less so than nylon. I believe Vesconite is current favourite.

FWIW just re-assembled the rack pre-load system on my six year old 31,000 mile Roadster with barely any steering play. No moisture in there but liquid grease. Plunger part was a very snug fit in threaded adjuster so took a smidge off with oiled wet and dry to offset any further expansion. Satisfying pop when greased and pulled out. Test drive revealed steering less lively over bumps so a small but worthwhile improvement. Absolutely no play at wheel now either.

Important not to put more than a smear of grease on plunger/spring/adjuster assembly, to avoid hydraulic lock up when finding fully screwed in position, before backing off.

Having like Heinz experienced intermittent clicking from the steering, the rack adjuster suddenly became worthy of investigation.

On releasing the 1 1/2" AF hex nut, star washer and unscrewing the threaded adjuster, the ID of the adjuster cylinder was measured at 20.0mm whereas the OD of the nylon follower was measured at 20.3mm!

I used a sharp chisel with the follower mounted in the bench drill to remove the excess nylon.

All reassembled with a dash of gearbox oil, a smear of grease and preloaded to fully tight minus a quarter turn of the adjuster.

No more clicking noises and no play at the steering wheel.

Heinz, thanks for posting this topic. About ten years ago a mechanic of (louwman, durch dealer) noticed some play in the steering of my 2009 Roadster. He stated that the expansion of nylon follower was to blame. He carried out the mechanical treatment you described. Indeed, it fixed the “play”. On the occasion he said that he saw this regularly, so, I never thought of posting the issue and its solution. Point is that the play slowly inceases and at the time, and can therefore remain unnoticed. I thought: it is a Morgan, this is normal. Well it is not. Hence, good you made the community aware! Safety first.

It's actually the most important unknown known that we've had on TM for a long time. Clearly the Dealers are aware but this issue has not been generally aired amongst owners.

So Heinz did us all a huge favour bringing this into the light.

The 4/4 has the narrowest tires and the lowest weight. Both together mean that the steering is very light around the center position when driving straight ahead, lighter than the power steering of other cars. This had the effect that the steering behavior was quite strange because it became even lighter with the stuck nylon follower. The resulting play at some points of the rack may have been marginal but it was enough that the car did not drive in a straight line line and always required small corrections. In a Roadster or Plus4, the steering forces are generally higher and the tyres are wider so you might not feel the influence of a stuck nylon follower so clearly. But the corrections when driving straight ahead could also be noticeable. Be that as it may, a nylon follower that has been made to work again provides a nice steering feel that is transferred to the hands and always corresponds with the impression of the same gentle spring pressure of the spindle on the rack. As a result, the effort required increases steadily and gradually when I turn a corner. Previously, the effort required when turning into a bend was not so gently rising. And it drives straight ahead again very nicely by itself.

Ah Dave!

I had a lathe too, being an engineer I had acquired an old'ish school lathe which was small and compact but had a good level of functions. When I moved from Kent to North wales I had a lot of workshop tooling to move and moving to a bigger space I had decided to up grade the lathe when settled so gave the old one to a friend before the move.
That was in 2000 and I still haven't got around to it yet although I still miss the lathe on probably a weekly basis---------guess that means I'm not settled yet!


One little tip for those of you who are now wondering if your nylon spring loaded steering plunger is sticking. .Jack the front of the car up at the front cross member and raise both wheels off the ground then manually turn the wheels from side to side, making sure first of all that the steering lock has been released! The advantage here is the reverse of the steering wheel input and although heavy it should feel smooth and evenly loaded. don't get confused with the oscillating type feel that will be fed back through the wheels, a ryhmic feel like pulsing, this is normal and is in fact the effect of the universal joints throughout the steering column when rotated by the front wheels. the plunger feels more like a creaking micro judder and is there all the time. you will probably feel it through the steering wheel if you move it slowly with the wheels also raised.

My own view having just reset the rack pre-load is that if your car has a Quaife rack (2007 on), is over six years old or shows any signs of too lively steering and/or any play, then take the adjuster apart. It's very easy to do with correct tools once the lock tabs of washer under 38mm locknut have been bent down.

My plastic plunger/rack follower hadn't seized although was a very snug fit so maybe not far off, which is why I took at tad off with oiled wet and dry. I suspect it's expansion is more time than mileage related though.

On re-assembly I adjusted after tightening down then backing off the recommended ¼ turn. Afterwards I measured the before/after difference of threaded adjuster above locknut. It sat just 0.05mm lower equating to little more than ¼ turn of slack taken up.

Having driven the car yesterday over far more than a quick test drive I can confirm this small adjustment has made a noticeable difference. In essence the wheel feels calmer over bumps with the skittishness that had built up over time having
gone.