I posted this tip on a well known Porsche Cayenne Facebook forum, having mentioned the manufacture name only once and having showed no branded photos in my modification tips post – it was deleted – go figure.
So here it is on my own web site for anyone with a need to view. It shows how to save yourself an amount of cash, by not having to purchase the optional custom JXB Performance Support Brace, and my method simply utilises the Porsche Cayenne OEM brace, with the addition of two drilled holes, which saves you a load of grief in installation time and effort.
Having loaded the car for a Christmas break I got about 20 miles from home and the noise from underneath sounded just like a flat tyre at motorway speeds, slower speeds and the input of any acceleration resulted in heavy thudding from the transmission tunnel. A common problem to the model, extending to the VW Toureg, Audi Q7, and many other listed vehicles of similar build. Having limped the car back home and transferred luggage to the Camper we continued our holiday break…
The Prop shaft (drive shaft, in some territories) Centre Support Bearing repair job awaited on my return, it was -8C outside and a snow covered drive, so a quick confirmatory glance with a torch, and then to the computer to order the correct part required. I chose the JXB Performance solution, a circa £300.00 part, that allows the in-situ replacement of the failed support bearing without the huge labour involved in dropping the full prop shaft – which on the Cayenne 955/957 models involves removal or a very least dropping the exhaust system to gain access to the rear prop flange bolts. You then need the minimum of a reconditioned shaft, often service exchange and then a refit job. Not the option for me.
There seems to be two aftermarket options available for this issue, however the JXB Performance bushing kit appeared to me a better engineered solution. Feel free to research, look at the companies, install videos etc and decide for yourself. I purchased my JXB Performance Driveshaft Centre Support Bearing Carrier Upgrade for Porsche 955/957 – part number 95501A0-S. from AKS Tuning Ltd. in the UK, it arrived next day.
There are loads of installation videos online so I am not going to reinvent the wheel in describing what is required to be done to complete the job, however if you plan to install the kit without the custom JXB support brace, you will have to drop the front flex drive on the prop shaft to allow access to fit the bushing.
What can be seen in the photos below, is that by making a paper template of the base of the support bearing you can accurately drill two suitable sized holes allowing you to insert a long hex key through the drilled OEM steel support plate to fix the two halves of the JXB bushing easily together, without dropping the front of the drive shaft to gain the necessary access to bolt it all together, which of course all of which isn’t required if you decide to purchase the optional JXB Support Brace
Once fitted, and I chose the ‘Street’ Compound rubber, the driveline feels taught and there is no vibration or noise transfer to the passenger compartment, in fact in my case it was pretty much as it was from the factory.
A Happy New Year and many thanks for your support in helping to keep the free automotive repair resource going!
My Mercedes ML320CDI (2007) had a mind to play up on the motorway and put me in some hot water with regard to the vehicle being totally disabled.
Looking back, I had noticed a few symptoms over a month or two that I had not connected to the real underlying issue that would eventually completely put me out of action on the M6 only ten miles from home!
The month running up to event I had noticed an occasional hard change down at slow speed when coasting to a halt, I simply put this down to the foibles of the 7G-tronic gearbox and ignored it. There had been a very slight groaning noise on particular right hand bend on my daily journey to work and again, unless I was listening for it it just got ignored. Then one particularly wet day the ABS, ESP and Tyre pressure monitoring inoperable warning appeared on the dash – everything seemed fine, I found a safe place to turn off and restart the car, everything was fine.
I had a very early morning trip up to Liverpool and it was an awful day with heavy rain and large amounts of surface water on the road, I got to Liverpool without drama and pulled up to a set of traffic lights as I slowed there was a really loud groan, almost like a passing jet under power take off – I actually dismissed this as just that, thinking it was a low flyer out of John Lennon Airport. I parked up and went about my business.
About three o’clock I set off from the carpark, through the town and joined the M62 back home. Later joining the M6 southbound is where the fun would really start!
Outside lane of one our marvellous SMART motorways saw the dashboard light up like a Christmas tree, ABS, ESP and Tyre Pressure Monitoring not working. I eased off the throttle and it became obvious the car was holding in a single gear. As I could not quickly get over to lane one (not as it would have done me any good as there was no hard shoulder now thanks to the SMART motorway improvements!). It took me a few miles to get myself to a place of less burden. Each time I pressed the throttle the ESP triangle would flash stopping doing so when I lifted off the power. I made the decision I was going to try a rolling restart in an attempt to reset the problem – big mistake. After selecting N and turning the engine off and on again I had no drive at all and the gear selector stayed in N no matter what I did with the lever. Attempt 2: off and on, this time I had drive in what seemed like second gear, useful rpm’s at 50mph! Enough was enough and given the circumstances I decided to hang in there and sweat it out, locked in a single gear – it was certainly far better for me than the ‘no drive at all’ option I had adopted earlier.
So I got off the motorway and pulled over in the nearest layaway I could find – what a relief! A restart and off we go, the ABS and ESP warnings still lit, as soon as I hit 4mph the brakes activated on what seemed like all wheels and bought me to a halt, it was impossible to move the vehicle above a slow walking pace. Many restarts later it was obvious this was not going to rectify itself and I called the RAC….. That will be four hours wait sir! I called up a friend as I was only ten miles from home and he took a detour past my house and collected the Autel code reader en route. He arrived some minutes later and we plugged in. Wow! anything speed related had flagged a fault, including gearbox, steering, ETC/ESP Instrument cluster, the lot. I cleared them off one by one which eventually allowed me to clear every warning on the dash. I set off again and exactly the same happened, 4mph and all wheel ABS braking arrested the vehicle to a halt with no intervention my foot apart from pressing the ‘go-go’ pedal like mad, which I will add had no affect whatsoever.
So sit it out for the RAC man… I had already described the fault over the telephone as ‘no drive’ and hoped they would send the appropriate vehicle to recover me. They did, three and a half hours later this recovery vehicle arrived, my jaw dropped…
The rest is history, the ML was delivered home in style, I was impressed by the way the set up worked and to be honest was fascinated by the mechanical wizardry of it all. My car was limped into its parking place, the gates closed and left overnight. Still I might add with not one fault showing on either the dash or code reader.
The following day I had convinced myself that it was a traction control problem and coupled up the Auto in live data mode. A short run down the road at crawling pace revealed the rear left wheel speed sensor to be counting at about half the impulse counts of the other three wheels. Sure enough as the speed rose above 4mph the brakes applied and halted the vehicle.
Off came the wheel and the sensor removed, there looked little wrong with it, no rust debris stuck to it as you often find. I used a torch down into the sensor pocket and it looked clean and dry. I have seen similar sensors on Jaguar hubs that live in a debris filled pocket that builds up and wears into the seal of the hub bearing. Once water gets to play in here the magnetic poles embedded into the bearing seal start to delaminate. Once this happens there is no hope in changing the sensor. The complete hub bearing has to be replaced to renew the magnet pole ring within the bearing oil seal. Fortunately the ML’s seal looked in fine condition as far as I could see down into the sensor pocket on the hub carrier.
The later wheel speed sensors we see on these and later stable Mercedes are ‘Active’ sensors. These have some electronics built into them and are basically a ‘Hall Effect’ device that reacts to magnetic fields passing through their target area. The ring of ‘miniature magnets’ that are moulded into the bearing seal are ordered North, South, North, South and so on making up a full 360 degree angular device. Because the sensor is electronic it can determine wheel speed far more accurately than older ‘Passive’ inductive types (the toothed wheel of yester-year) because of the modern arrangement the sensor can determine rotational speed from a standstill and even detect direction of rotation!
I think the problem with my sensor was it was only detecting either North or South poles from the sensor ring and not both, this would have halved the impulses measured as I saw on my live data. There was no fault present since I cleared them because the ESP traction control was controlling exactly as it should given the wheel speed information. Let me explain. One wheel gives speed information slower than the other three, the electronic controller thinks three wheels are spinning and applies forced braking to those faster moving wheels to control the vehicle. Of course this is not actually the case but in terms of what the controller sees it is reacting as it was designed.
Replace the sensor. Very simple one small bolt on the hub carrier and the sensor withdraws. There is a single connector about 250mm away on the upper suspension arm from which the sensor simply unplugs. Mercedes Benz want an eye watering £99.00 plus vat for a genuine ATE wheel speed sensor – err don’t think so guv! Our local motor factors had a pattern part on the shelf £24.00 No brainer?
So replacement sensor fitted, a final clear down of any fault codes and we were away. Perfect fix. A couple of other things became apparent, the slow speed gear change harshness had gone, the slight groaning no longer present in the particular corner on the way to work and how about this… – The Hill Start Assist actually worked far better than it had ever done, only previously working as well in reverse! Transformational and a fantastic low cost fix to what appears on the face of it to have been a ‘big ticket’ job.
Mercedes Sprinter 2006-on and Volkswagen Crafter Clutch Master Cylinder Replacement.
Having recently replaced the clutch and slave cylinder on a Crafter CR35 with a LUK Rep-set, the driver complained that whilst setting off the clutch seemed fine, after a short period of ‘town driving’ the clutch became difficult to disengage.
What this actually meant was there did not appear to be enough travel in the pedal to fully clear the clutch and pressure plate – meaning there was ‘drag’ after the initial ten or more clutch presses of the day. This drag in turn made gears difficult to engage and at some point even disengage/pull out of gear, with the clutch pedal hard to the floor. Drive take up seemed to begin right down at the bottom end of the pedal travel.
Having re-bled the system to ensure there was no air lurking in the system, I decided that the clutch master cylinder was at fault, possibly passing pressure and not allowing the full capacity of hydraulic fluid to be transmitted into the slave cylinder, shortening its stoke acting onto the pressure plate spring. It is worth noting that I had previously correctly ‘set’ the clutch cover plate assembly tension as described during installation described elsewhere on this site, so could confidently discount that as being any issue.
The replacement of the clutch master cylinder, whilst being a little bit awkward to get to, is quite a straight forward job and can be easily attended to in just over an hour – start to finish.
The first thing to do is remove the hydraulic feed pipework to the clutch master cylinder from the shared brake/clutch master cylinder reservoir. There is a semi-rigid, ribbed plastic pipe that feeds the cylinder fed from a spigot on the side of the brake master cylinder fluid reserve. Work this off gently, quickly pushing on a suitable size ‘blanking’ hose to stem the hydraulic fluid flow. A short length of flexible rubber hose, bent double at the end and secured with a tie-wrap is an ideal temporary blanking plug. Any fluid drips while doing the change over can be caught in a rag placed beneath the spigot.
The next pipe to remove is the rigid steel high pressure pipe from the nose of the master cylinder. This connection protrudes into the engine side of the bulkhead to the right and slightly below the centre of the brake vacuum reserve (Right hand drive vehicles). To release the pipe from the master cylinder there is a small retaining clip that has to be pulled downward to release the high side hose. Its a fiddle to get at, but is best attended to with a 90 degree pick or suitable small screwdriver. Note – the clip is ‘retained’ and only pulls down about 10mm to release the pipe, once the pipe is removed, push the clip back up to the locked position so it can be pulled through the bulkhead grommet from the inside without fouling. Once the clip is pulled down, the pipe is released by grasping it and pulling outward, again be prepared for a little fluid leak.
Now both feed and delivery pipes are disconnected attention can be drawn to the inside the drivers footwell pedal box area. First remove the circlip and peg that retains the master cylinder rod and eye to the clutch pedal, again a 90 degree pick works well to do this with the restricted space available. Now remove the two 10mm nuts that hold the twin through-pins holding the master cylinder to the pedal box frame. The opposite end to the nut is an E10 reverse torx, which will need to be held whilst undoing the two nuts. Slide both pins out from the pedal box towards the centre of the vehicle, once this is done grasp the master cylinder and pull it downwards and out into the footwell. Only pull the cylinder sufficiently to access the feed pipe spigot and ribbed hose which can be removed in the same way as the other end on the under bonnet brake/clutch reservoir. Once this is off, the cylinder can be taken from the vehicle.
Unbox the new master cylinder checking that is the correct part, remove its protective blanking plugs and offer it into the footwell, reconnecting the reserve feed pipe. Have an assistant gently pull the ribbed pipe back through the bulkhead grommet as you carefully feed the cylinder body back into position between the faces of the pedal box bracket. As it nears the correct position, use a suitable sized allen wrench to align the through-holes for the two fixing pins. When aligned, slot back the two pins and secure them using the E10 and 10mm wrenches. Feed in the eye of the actuator rod between the faces of the plastic pedal lever, aligning both parts to allow you to push through the peg and refit the retaining circlip.
From the engine bay, reconnect the high pressure pipe to the master cylinder nose. Just push the pipe in with its tapered seal until it ‘snaps’ locked in the set spring clip. Now remove the temporary bung and replace the fluid feed pipe back onto the reservoir spigot, checking for correct fitment and attending to any leaks.
Connect up a pressure bleeding system such as the Gunsons EZee-Bleed and pressurise the system. Its worth noting that without a pressure bleeding kit this job is pretty much impossible, as is true with most concentric clutch slave cylinder systems, especially ones having been fitted with a new (empty) dry master cylinder!
Crawl under the vehicle with some rag and open container, open the bleed valve to the clutch slave cylinder by rotating it. There are two types – a conventional steel bleed nipple that will need a small spanner or a plastic turn valve type where no tools are required, simply turn the tap clockwise to allow fluid flow and turn back to stem it. The pressurised fluid will flow from the bleed nipple, when it flows clear, without spluttering or visible, air close it off. Have your assistant operate the clutch pedal up and down a couple of times, both with the pressure bleeder connected and then with it depressurised. Repeat the procedure until a firm pedal is present. Even the smallest downward movement of the clutch pedal should result in some movement of the slave cylinder piston (thrust bearing) against the clutch diaphragm spring. This can be seen with a torch through the opening in the gearbox bell housing where the slave cylinder bleeder extends. If you are happy, then remove the pressure bleeder and check the reservoir for the correct fluid level.
Clean the work area with warm soapy water, as if you have spilled any brake fluid during your work it will easily remove paint over time and encourage rust in the engine compartment if left unattended.
The OEM part number of the clutch master cylinder is: A 906 290 02 12
It is possible to get just a ‘seal kit’ for the master cylinder and rebuild the existing unit, however further compounding the problem with the unit described here was the steel pedal pivot had worn the eye of the actuator rod oval, as the picture below shows, resulting in restricted or diminished cylinder stroke. This is not a ‘kit’ part (only contain seals) so I would recommend only fitting a complete part. These replacement items are available circa £30 in pattern parts and in my view are a good investment over just replacing the internal seal kit.
One of the fleet Crafters pulled into the yard and the driver shouted in best Anglo-saxon that there was an issue with the side loading door and that there was a load of ‘wires’ hanging! On carefully opening the side loading door and beginning to slide it back on its runners all became apparent. The flexible cable tray (chain-tray) was in several pieces and the electrical cable it was supposed to house draping down dangerously in the area of the bottom door guide track.
Most of the plastic chain-tray looked to be just unclipped from itself and would reattach to make a continuous ‘chain’ again, however there was one or two link sections that were broken, including the last one in the snake that connected directly to the lower stay of the bottom door roller. This lower stay-section has a plastic snap-in moulding beneath, this routes the bowden control cable from the handle mechanism to the runner latch operating a release for the sliding door when it is fully locked open.
The only way to repair and re-route the cable correctly within the chain tray is to remove the step plate/lower runner guide moulding. There are a number of fastenings that hold the step to the body and these are well hidden in pockets beneath the tread under removable (well disguised plugs) once these are removed with a thin blade screwdriver and careful levering they reveal a number of Torx bolts. These protrude to the underside of the van and in many cases benefit from a wire brushing and penetrating oil from underneath before attempting to undo them. In addition to the selection of fasteners on the step tread, there is one either side on the raised sections at each end under a plastic top-hat plug (25mm diameter) once removed with the small clip-in plastic loom cover at the bulk head end the step will lift out revealing the cable and tray.
There will be a huge amount of debris, soil, nails etc under hear and now is as good a time as any to clear this area out so as to prevent any build up obstructing or wearing the roller on the lower guide of the door track.
Under the step is a black plastic flat cover, this clips into a raised plastic U section that supports and guides the cable chain tray as it rolls in and out of the step as the door is operated. The chain tray is attached to the U section by a snap clip that ties it to the bulk head end of the U section. As my chain had lost two links through damage I moved this by the appropriate amount further along the U section to compensate for the missing length. I simply cut a new slot with a craft knife into the U section and snapped the locator into the section.
The clip in part that resides under the lower roller arm of the door was a little tricky to put back into place as both the electrical cable and latch cable run in slots either side of the moulding, these want to slip out as you attempt to clip it together. The electrical cable lies in the moulded lower section and hooks round into the chain tray attachment lug and onward into the reminder of the flexible cable management. Once all clipped back in lace I added a couple of strategically placed cable ties to hold the end together, engaged in the metalwork.
Test opening and closing the door without the step and watch to see how close the chain tray passes the door hold-back latch pin fastened to the rear of the step cut out. This will be close. Too close for my liking and probably the reason the cable management got ripped away in the first place. I loosened the latch pin plate screws and moved it up a small distance to clear the chain tray. Ensure the latch on the lower runner arm still meshes with the pin and aligns well.
Once the cable tray is attached and tested free to move, the step section can be refitted and the fixing pocket retainers refitted. The door should now be just as it was before the cable tray got broken.
If ever there was a job that took more time to consider than actually physically tackling the task then this is it!
Replacement of the rear coil spring on the W639 Vito is ‘super-easy’ and should not be a problem for even the most inexperienced home mechanic, saving you a great deal of money in the process.
First jack up the rear of the vehicle from the sill end buffer (jacking point) nearest the rear wheel with the broken coil spring. Remove the road wheel and place a stout wooden block beneath the swinging arm, directly under the spring cup and carefully lower the vehicle body on the jack. Lower it so that the swinging arm transfers some of the weight of the vehicle onto the wood. Now remove the lower shock absorber bolt (21mm socket and bar) from the swinging arm (or rear radius arm if you prefer that term).
Jack the vehicle once again, up and away from the wooden block. Once raised, use a lever if needed to pry down the rear edge of the swinging arm to release the spring from the upper cup/bump stop. The spring will come out easily, usually along with the rubber cushion mounting pad, either top or bottom as it feels the need.
Simply re-fix the mounting pad to the new coil spring, lever down the swinging arm once more and insert the new spring. Place the wooden block under the swinging arm again and lower the vehicle carefully with the jack to take weight onto the block, beginning to compress the spring to a point where the lower shock absorber eye is parallel with the threaded portion in the arm so the bolt can be easily replaced and retightened.
Check the ‘seating’ of the spring and if all is well – replace the road wheel and put the kettle on.
The Sachs OEM replacement springs (Sachs part number 627221840) that were used in this instance to replace the ‘stock springs’ were made of far heavier weight steel stock and did not taper in thickness towards the extremities of the coil ends as the original did. Assuming that because of this the new springs were rated as heavy-duty they would be best changed in pairs, its a simple job and there is really no excuse to change just one and have odd springs fitted on one axle – for peace of mind always change them in pairs!
