Technical SL R129

Slight vibration heard when applying slow speed steering lock – Mercedes SL (R129)

Mercedes SL (R129) Rubber bobbin bushes

When I last went to the tyre shop the fitter drove the car into the bay, as he manoeuvred I heard a low frequency vibration from outside the car.  It was like a flapping vibration, two parts vibrating against each other and it was quite loud.  I knew it was nothing to to do with the auxiliary belt or its tensioners as I already inspected these components and found them to be sound.  So what was it…?

Mercedes SL (R129) Rubber bobbin bushes 2

It wasn’t until a few weeks later when I was replacing the steering idler arm bushes that I noticed the metalastic bush (rubber bobbin) on the front cross brace on the passenger side had deteriorated and parted company.  It was not instantly visible as faulty as the tension that is placed on the bush pushes the parts together so it can’t easily be seen.  Just give your bushes a little pry to see if they have parted company with the bonded threaded sections.

The cross braces run from the centre of the car, under the engine, to just behind each road wheel in a diagonal formation.  They are securely bolted fore and aft to the chassis with a single bobbin type bush in the centre run of each.  The bush is bolted to the brace then upwards to the chassis and I suppose is in place only to prevent it vibrating or flapping over its length – precisely the issue I had.

Mercedes SL (R129) Rubber bobbin bushes 3Mercedes SL (R129) Rubber bobbin bushes 4

I searched for replacement parts (bobbins) and was horrified to see that they were priced between £8 and £12 per bush!  Now, although I don’t mind buying parts that are required, I just think this is a ridiculous price to pay for what is in effect a piece of rubber with two threads on!  Especially as it was a non-critical part.

Searching deeper for an alternative I caught sight of a supplier in Hong Kong advertising the correctly dimensioned bush for 0.99 pence including delivery – thats more like it!!  Link to product found here

Mercedes SL (R129) Rubber bobbin bushes 5

Ordering six bushes I only had to wait two weeks and the package arrived.  Six bushes of what looked good construction and quality just what was required for the bracing bars. I then remembered the air box support bobbins had gone the same way and by chance the parts ordered also fitted this application perfectly.

Mercedes SL (R129) Rubber bobbin bushes 6

So for £6 I had repaired/replaced the two air box mounting bobbins and those on both bracing bars, plus two spare!.  As suspected the flapping sound of the bracing bar, induced by the pulsing of the power steering pump at low speed had now gone – Success!

 

Mercedes SL 320 (R129) Steering Idler Arm Bushes – Replacement

In the quest for the best possible drive and ride I had detected a slight amount of front end wander and tram-lining on rutted tarmac.  This was a similar feeling to someone just tugging the steering wheel and forcing the car to steer slightly in an unexpected direction.  This was not a serious situation, just one that I knew shouldn’t be there.

OLYMPUS DIGITAL CAMERA

I checked the lower control arm bushes and ball joint on both lower arms, along with all six ball joints in the steering route.  The steering gear checks are easily carried out by simply gripping the ball joint to be tested while an assistant wags the steering wheel left to right.  Any play will be felt in the joint – any perceivable movement between the ball pin and socket, then replace!

OLYMPUS DIGITAL CAMERA

Pay special attention to the drag link ball joint ends that links the pitman arm of the steering box to the idler arm.

Look carefully at the top of the steering idler arm pivot while the steering wheel is being swung, any up, down or side to side movement that can be seen with the eye indicates the bushes require replacement.  Bushes in a kit, with a new through bolt and washers are appx. £130 genuine Mercedes or about £40 for URO imported pattern parts.  (Not the best make in the world – but as Lemforder have recently discontinued their offering, the only available option to genuine parts)

OLYMPUS DIGITAL CAMERA

On the SL320 (R129) take a 24mm combination spanner and place it over the head of the idler bolt, let the spanner rest against the engine mount.  From underneath, use a breaker bar short extension and 24mm hexagon socket and begin to undo the nut. Once free, exchange the breaker bar for a ratchet and remove the nut and washer. Tap through the long bolt and remove noting the order of the cup shield and spacer washer.

Removing the old bushes is best done first from the engine bay.  Use a piece of steel tube about 75cm long and place it on the steel lip of the lower bush.  Strike the drift/tube from above in the engine bay with a stout hammer and work your way round the bush lip, driving it steadily out of the chassis tube.  When the lower bushing is removed, get underneath and use a shorter tube/drift through the chassis tube to drive out the upper section.

OLYMPUS DIGITAL CAMERA

Lubricate the new bushes with red rubber grease. Pop the old through bolt into the new bushing and position it over the chassis tube top, drive it into the tube using your drift/pipe centred over the through bolt head as far as possible.  When the bush is fully home drive the lower section of bushing in from underneath.  As soon as the thread can be seen,  fit the old nut and tighten it up.  This should draw the bush home, reaching the end of the available thread take out the through pin and thread it through the idler arm and retighten until both sections of the bush are completely fitted.  When satisfied replace the old through bolt with the new one, build up the pivot and tighten the nut and bolt fully.

r129 Steering Idler Bush Kit

Mercedes SL 320 (R129) Steering Idler Arm Bush Kit Part Number: 129 460 0019

R129 Exploded steering parts diagram (LHD)

Rear Suspension Refresh (R129) Mercedes SL & (W124) – A Wandering Star!

thin

Even though the Mercedes SL320 (R129) passed its MOT in December with flying colours, there has always been a slight uncertainty at speed with regard to wandering.  This is not ‘lane changing’ wandering we are talking about here, but just a hint of rear end steering that needed to be corrected in the 60+ mph range when buffeted or the road surface commanded, by the way of uneven camber or rutting of the tarmac.

Rear Suspension Refresh (R129) Mercedes SL & (W124) 1

Either way, it would be nice to sort this minor issue as the SL is such a pleasing drive and you do just ‘Waft’ along on a magic-carpet ride, with surety even when pushed.  I had previously had the vehicle in the air and ‘barred’ the various multi-link suspension components in every way possible.  Although the rubber bushes in each one of the pressed steel control arms was almost 20 years old, they were together and were just showing slight signs of perishing, with no real visually alarming deterioration.

Rear Suspension Refresh (R129) Mercedes SL & (W124)

Even gripping the wheel and then exerting huge forces with a crowbar under the tyre resulted in what seemed a taught rear suspension layout, seemingly not wanting for anything. But something was not just right and it was bugging me!

Previously I had already fine tooth-combed the front end, discovering that the lower wishbone (control arm) bushes were starting to get a little saggy, but were holding there own.  Visually the worst was the off side front rear bush in the set, but even when barred to extreme it still held firm.  A job for the future.  The front dampers were a little worn with only the slightest play in the rod/cartridge bush at normal ride height – again nothing to cause the wandering or write home about.  It goes without saying the steering components came under detailed scrutiny and in every case proved wholly serviceable, with no unusual tyre wear either on the front or rear.

Rear Suspension Refresh (R129) Mercedes SL & (W124) 3

So what to do…  well I decided the rear steering was obviously a result of some issue with the rear suspension, as the car would shift or wander needing correction through the steering.  If this was front end wander, you would be fighting the wear in the normal course of driving, over correcting as you drove.  So the decision was – it was the rear, you could kind of sense it happening under your seat, as you are sitting almost on top of the rear axle. It was almost as if you were being slightly ‘pushed’ sideways from the area under the seat.  Characteristics were unusual in that there seemed no repeatable reason for the movement.  I tried driving in ruts LHS/RHS, applying power, driving on white lines etc. It had a mind of its own – only the car knew when it wanted to do it!

Rear Suspension Refresh (R129) Mercedes SL & (W124) 4

Having double checked the rear sub-frame mountings and bushings for wear, I made the decision to jump in with both feet and totally refresh the rear suspension – maybe I would find something along the way that would directly point to the ‘Wandering Star’…

I sourced a complete kit of rear suspension parts containing four control arms per side, all new bolts, fixings and washers. The Delphi Kit price was very good value as the component parts individually added up to almost double the kit price by the time you had purchased – new camber adjustment bolts, washers and lock nuts etc.  On opening the kit, it was obviously good quality and proved excellent value against OEM or other available parts.  All the contents were checked against the originals as they were removed and bush centre to centre dimensions were crack on.

Rear Suspension Refresh (R129) Mercedes SL & (W124) 5

So on with the job, side at a time…

Raise the vehicle using the rear chassis jacking point and remove the road wheel.  Get a sturdy support to hand- blocks of wood are ideal, these will need to be inserted under the rear sprung arm to take the weight of the vehicle when necessary  during the work, especially when finally tightening the suspension fixings under normal ride height conditions.

Remove the plastic Spring Link cover by undoing the two 10mm head self tapping screws and prying off the cover from the lip on the arm.  Now adjust the jack so half of the weight of the car is supported on the jack under the chassis and the other half resting the Spring Link, supported by using your wooden blocks.  You will need to adjust the weight distribution at times between the chassis and Spring Link, by raising and lowering the jack slightly.  This will release tension from the suspension links allowing you to easily withdraw the various pins from the eyes and hangers as and when required.

Suspension set up W124 -1

Start by removing the upper forward arm, The Pulling Link. Your tools of choice for the job in hand will mainly be a pair of good 19mm combination spanners, a 17mm combination spanner, 17mm socket and 18mm combo for interlocking with the other spanners to increase leverage to break any rust.  The new fixings/bolts and pins will require a triple square splined tool, it would be better to check exactly what size you need by first inspecting the parts in the kit when you purchase it. A heavy copper hammer and a sharp hack saw will also be required!

Tightening torques for bushes:  Body end = 70 Nm – Wheel end= 70 Nm with M12 thread, if M10 thread then 40 Nm.

 

Suspension set up W124 - 2

Open the kit of new parts and select the correct arm and refit it to the car, once fixed, just nip up the fixings. Lower the chassis to place pre-load weight onto the suspension, then fully tighten at the two fixing points on the Pulling Link, raising the vehicle again when done.

Now remove the Pushing Link, (Forward lower arm without a ball joint) This will have a plastic trim cover clipped onto it, this can be transferred to the new link when you refit the item. Begin to remove the Tie Link using a 17mm spanner on the nut attached to the hub carrier, if the ball joint begins to spin you may need to use a hexagon key in the taper end to hold it while you undo the lock nut completely. If it does not spin, you will get the nut off easily, then using a ball joint separator (Pickle Fork) part the joint.

Rear Suspension Refresh (R129) Mercedes SL & (W124) 6

Tackle the other end on the Tie link chassis bushing by undoing the 19mm nut.  Make sure you paint mark the adjusting eccentric cam so it can be returned to its correct position on reassembly.  Typically this fixing bolt will be seized.  It has a longitudinal slot in the bolt to key with the adjustment cam.  In use this allows water to seep along into the joint and internally corrode the alloy bush to the steel pin – you may be lucky, but probably wont be!  Faced with a seized through-bolt, your only option is to cut off the bush and bolt with a hacksaw.  Begin your cut from underneath on the first alloy step of the bush, on the triple square end. Don’t try and cut the steel outer as you will be sawing for ever. Short strokes will be allowed and it takes a while to cut to a maximum of 90 per cent through the bush and bolt.  Any further and you will begin to cut the chassis or hanger bracket, so be aware of your limitations while sawing.  When you have cut to the maximum allowable depth, wire brush the triple square adjuster.  Insert your splined tool to its maximum, if you can only manage a poor fit, don’t go any further until you have cleaned the splines and can get the tool tip fully home. (rounding this head off at this point would be a disaster)  Once the spline tool is fully home, place a 10mm spanner on its shaft, interlock an 18mm combo spanner and turn the bolt, hard – if you have cut through to your maximum, the bolt head will shear and the end will fall off.  The joint can then be manoeuvred out of the hanger and thrown down the garden!

Rear Suspension Refresh (R129) Mercedes SL & (W124) 7

To fit the new Tie Link, slot the arm into the hanger, align the taper of the ball joint and tighten this first using the hex key and 17mm spanner.  Then align the hanger end, inserting the new through bolt (cam adjuster)  Mark the parts in the same way with paint, copying the exact positions from the removed components.  Lower the chassis to support the weight of the vehicle on the Spring Link and tighten the adjuster fully through the hanger, whilst maintaining alignment of your paint marks.

Raise the vehicle again and refit the Pushing link with its plastic trim cover, this fits between the front of the hub carrier and chassis. Use the same raise/lower technique with the jack to correctly stress the rubber bushes on tightening.

Rear Suspension Refresh (R129) Mercedes SL & (W124) 8

Move on now to replace The Camber Link, use the same above procedure to refit the last of the new components.

Check your work thoroughly, refit the plastic Spring Link cover and then the road wheel, finally lowering the car to the ground. Proceed to do the suspension ‘refresh’ the other side of the vehicle.

It is worth while mentioning that while individual links are off the vehicle, it is possible to test out the condition of the bushes in the Spring Link inner and outer locations, these should be firm and without play.

The complete rear suspension refresh job should take about three to three and a half hours a side, as although straight forward, space is restricted and work is hampered by suborn and seized bolts.  Either way, with a little patience and care it should go well.

So having completed the job it was time for the road test.  The biggest thought in my mind was… had I wasted my money!

I started the engine and selected drive, the familiar muted thud that had always been there when slipping the selector to D to move off had gone!.  I did not believe it, so I did it again – sure enough the slop when taking up the drive had gone.  Lets continue…

Out of the street turning out and into narrow roads, the car felt noticeably different, tighter.  I was unsure if this was psychological mumbo jumbo, but that is how it felt.  Amazingly the steering straightened up more positively out of a turn, pulling out onto the familiar main road proved this without any doubt.  Applying throttle on then off, felt no different, which was good news – because it meant that combined with the fact the car steered perfectly straight without drifting or pulling, meant that the Tie Link adjuster had gone back in a near correct position, maintaining a useable and balanced toe in figure for the rear wheel set.  Opening up the throttle showed that the work was well worth doing, the car no longer felt vague, and did no longer have a mind of its own wandering as it did before.  Result.  The most amazing thing for me was to lose the drive uptake when engaging gear from neutral or park, this was indeed unexpected.

Rear Suspension Refresh (R129) Mercedes SL & (W124) 10

It goes without saying that this is maybe the first time ever I could not convince myself by visual of physical inspection (on or off the car) that any of the joints were degraded to a point of causing this type of wander.  It just goes to prove that old soft, not necessarily collapsed bushings, in a Mercedes five link rear suspension set up has a cumulative effect on drivability.  If your links are are all old, the  rubber will exhibit a kind of aging related softness, this is without doubt time to change them and enjoy the improvements it can make – not just to the wandering, but also to steering geometry in general, add to that the new transmission firmness and the result –  Money well spent.

R129 rear suspension

If you were so inclined you could spend in the order of £175.00 upward having the vehicle 4 wheel aligned.  My own view is to maybe wait until I get around to doing the few jobs up-front before even considering this.  If I don’t get any abnormal tyre wear and drivability is perfect, I see no reason to have this alignment done, although without doubt it should be done in the real world.  I have read so many alignment tales of woe borne of the technicians inability to understand the complexities of the Mercedes W124/R129 series it could make things worse – you decide!

Interesting write-up on wheel alignment, front and rear – here.

If I was to review this DIY maintenance work honestly, I would say the resulting positives from such a suspension refresh were probably one of the most value-added improvements you could make to your R129/W124 for what is comparativley a very little monetary investment.

Enjoy !

 

 

 

LED Lighting Upgrade – Side Light & Interior – Mercedes SL (R129)

I decided to upgrade the lighting in the interior of the Mercedes SL (R129).  Previously I had modified the BA9S LED lamps in the dome light / map light and now wanted to tackle the footwell and puddle lamps (under door lighting). Link to dome light modification/LED fitment here.

The reason for the upgrade is that I like the reliability of LED’s over the T10 and festoon tungsten lamp styles.  The T10 often blackens almost to the point of no light being emitted and the festoon ‘end to end’ filament is not a robust design by any means, especially in applications that involve slamming doors and boot/trunk lids.  Apart from that the light emitted is more pleasing to me than the yellow light from older traditional lighting, but that is a matter of taste and may not be to everyones liking.

I will add that there are a lot of LED’s out there stating that they are ‘white’ when actually their output contains an element of the blue spectrum – this often causes problems at MOT or inspection time, as the testers seem to need to see a ‘pure white’ rather than one diluted with a blueish tinge – That gets the thumbs down under the – ‘No blue lights should be fitted to the vehicle’ rule.  In my view this is a little petty, given that in reality the emitted ever-so-slightly bluish light, is not even on the same page as ’emergency services blue’, but I suppose a law is a law.

While I was choosing suitable festoon LED’s to replace the existing tungsten filament lamps I came across some T10 push in LED replacement lamps.  These would be ideal for the sidelights up front in the headlamp unit, the ones I was looking at had built in SMD resistors to offset the lamp load so that they would not trigger the bulb failure dash warning lamp.

t10 led1

The T10 LED replacement that has an oversize base that will not push through the opening in the R129 headlamp

My chosen festoon lamps were ordered from China (Also with resistors so that I could use them in the number plate lamp holders too)   The T10 push fit LED’s were ordered from the UK – no guessing which LED’s were delivered first!

t10 led2

My chosen T10 sidelight replacement – what an amazing light output!

I had previously upgraded the side lighting on my Vito W639 and was going to use some spare LED lamps I had in the SL application.  The problem I had was the receptacle in the SL headlamp reflector was only just large enough to insert a glass T10 lamp (not surprisingly 10mm diameter)  The China T10 replacements I had in the drawer were a little oversize on the plastic moulding flange, and although I could probably have forced the holder and LED into the lamp housing, I did not fancy dismantling the headlight to remove an LED that had been pulled from its holder and had fallen inside, when or if I ever had to remove or change it!

sidelight led sl

Almost as good as headlights ! – well you get the idea.

I ordered up the UK LED’s and within a couple of days they arrived.  Expecting similar performance to the Vito LED upgrade, I fitted the T10 replacements.  WOW.. These were just amazing.  Pure white and very, very bright with the added bonus that they fooled perfectly the SL’s bulb fail circuit.  I could not believe how good these lamps were.  Indeed they were almost as bright as daytime running lamps and at night the forward illumination from the two LED side lights was just staggering. (see photos)

led side lights output

White light output with good intensity as can be seen here.

Within a few weeks, the delivery of my LED selection from China arrived.  Once the weather had improved sufficiently to allow me to open the doors of the car and work inside without getting drenched, I got to work to swap out the footwell and door card puddle lamps.

Mercedes SL interior lighting LED upgrade

Footwell and door lighting works well.

Pulling the lenses/holders was straight forward as was changing the tungsten festoon’s for the new LED units.  I was pleased with the results – again pure white and excellent illumination, now matching the dome lamp LED’s done previously.

festoon led

LED Festoon lamp replacement.

festoon led back

Heatsink for heat dissipation of the LED’s and built in resistor.

I fitted festoons with integrated resistors, not because they are covered by any lamp fail warning, but because I simply ordered a larger quantity of the lamps I needed for the number/reg plate lights.  The number plate lamps were also a breeze to change, unscrewing the stainless steel screws (2 per lens holder) and lowering the holders was as easy as swapping the bulbs and slotting the holders back in place.  These LED’s also worked brilliantly, they did not trigger any lamp failure and the light was nice and white (although I must admit – not as ‘piercing white’ as the front T10 LED side lights) Very pleased with the results indeed.

ledplate

Good illumination and LED’s do not trigger lamp fail warning.

As you can see the quality of the LED’s both from China and the UK is very good, they look well made and built to last. So far 6 weeks and no problems – not that I expect to have any, because the Vito’s upgrade was done some 18 months ago and the LED’s are still going strong.

The side light LED T10 type resistor equipped replacements can be found here.
The LED festoon type, with integrated resistor and heatsink, for interior and number plate illumination can be found here.

When time allows I have some dash and instrument lighting that is out and in need of attention, so that ones on the list!

Heavy scrubbing noise from front tyres when cold – (R129) Mercedes SL & Others

When I first came across this problem I was worried that I had serious front suspension trouble, in fact it sounded so like there was some part of the wheel/tyre catching on a suspension component I used to stop and check my tyres were still inflated!  This problem only ever occurred when the car was cold and had been standing all day or overnight and never revealed itself when the car was warm.  It was noticed when applying a generous amount of steering lock either left or right, needed to negotiate an exit from a tight parking position.

This went on for weeks.  I researched what the issue could be and all that was written was: Worn lower arm bushes, top mount worn , play in ball joints… etc – to be honest enough horror reading material to scare the most ardent of owners!  But I was not convinced, as I could see nothing wrong with anything and all components were in good order with no play, back-lash or wear present.

I came by this totally by accident, it was a YouTube video posted by a chap with an almost new Porsche 991 – the noise and vibration effect was identical to what I was suffering on the Mercedes SL (R129)

Although my tyres were past there best, still more than legal but approaching time to change I was convinced this was tyre related. After some investigation and reading obscure posts and questioning seasoned performance mechanics it became apparent that this was not an uncommon problem.

P1020014

Continental Contact tyres – worn but with some life left

 

The scrubbing/rubbing noise seems to be more prevelent with Continental Contact 2/3 tyres and often accentuated if the tyre is starting to cup or feather on the edges. However it is not a product of a worn tyre or even an anomaly of a particular brand – it is due wholly to steering geometry angles and cold tyres!

From my reading on the subject some Porsche dealerships have offered an opinion to owners that this noise or juddering effect takes place more commonly below ambient temperatures of 40 degreed F or 4 degrees C (That is most of the time here in the UK!) Owners of Mercedes vehicles have reported exact noises and effects similar to that experienced by Porsche owners.

Having spoken to several mechanics and in particular to one industry expert on the subject his comments are worthy of note:

Hi Steve, now you come to mention it, I think I have noticed that happening in some of my cars – and especially the 2004 Passat when I’m using full lock to get out of my driveway. I also borrowed a Porsche Panamera last summer, and from memory that did it, too.

I think it’s because modern cars have such a tight ‘lock’ that when you turn the wheel fully in either direction at least one of the tyres – the inside one, I guess – is almost literally being pulled/pushed diagonally across the ground, rather than rolling as cleanly as it should. I’d imagine it would be worse when the tyres are cold – ie less supple and less grippy than when hot – but then again the ambient temperature when I had the Panam was pretty warm. Maybe that has less bearing than the angle they are operating at…

So there you have it, it is a little known phenomena occurring mostly with cold tyres, made worse in some instances by tyre choice, wear or age. You live and learn….

Mercedes front tyre scrubbing noise

Replacement Pirelli P7 front tyres – ready to go on the SL