Technical Ducato Bumpstops rear suspension

[Threesheded]

Hi All,

Long time lurker first time poster. I have picked up lots of information from this site over the years and would appreciate some advice. I have decided to fit semi air suspension to my X290 Ducato. Prior to removal I sprayed some release oil into the top of the bump stop mounting. The drivers side rear bump stop was removed after about two hours of hammering, swearing, and eventually using a chain strap wrench (which subsequently buckled during the removal, giving some idea of the force involved). The mounting threads were cleaned up using a M10 x 1.25 tap and a fair amount of crud was removed. All well and good so far. Whilst attempting to remove the passenger side rear bumpstop it unscrewed about half way out of its mounting then the cage holding the bumpstop just started spinning, the weld securing the threaded stud to the bumpstop cage had failed . After removing the rubber bumpstop from its cage this was confirmed.
The first image shows the current state of the bumpstop cage, scratches on the failed stud are from me trying to get mole grips and waterpump pliers onto the portruding stud with little success.
For comparison the other attachment is the succesfully removed drivers side bump stop. Attempts to remove the failed bumpstop mounting with molegrips and waterpump pliers have been unsuccessful and the stud seems solid. The head on the stud is too large to get stud extractors onto it. It is currently sitting in penetrating oil but since the chassis side mounting nut is pretty inaccessible all I have been able to do is blind one side of the hole with plastic bags and spray the oil in between the chassis rail and the top of the mount.
I have been considering trying to grind some flats onto the sides of the stud to try get a shifter onto it, but access is an issue. My other option would be to try and get a mobile welder to come out and re-attach the stud to the cage with a more substatial weld, this would obviously give me a better lever to work with. The down side to using a mobile welder would be having to disconnect the leisure batteries which are under the drivers seat and require removal of the seat and swivel mechanism for access, and removing my refillable gas bottle system which is in a locker directly above the bump stop mounting. a right PITA.
I would appreciate any any other suggestions from the fine experienced forum users before I go down the mobile welding route.

 

[Anthony489]

Hi Threesheded

That's a fearsome amount of rust on a relatively new vehicle.

I suspect that the previously exposed spare threaded end of the stud which projected up beyond the captive chassis nut has rusted up and expanded. As you try to unscrew it down and through the nut, it's jamming up.

If I was tasked with this problem, I think I would drill out the remains. This is easy enough to say, but care and patience is needed to make it succeed. The idea is to start with a small diameter drill (say 3 mm) and work your way up through a succession of larger drills until the minimum hollow shell of the stud remains. The weakened shell can then be broken up/pushed out by running a taper tap up through the centre to restore the thread in the captive nut. It's essential to make the first hole truly central by starting with an accurate centre punch mark, and it's important that the drill bit is aligned to the centre line of the stud and not angled off. New-ish drills and lubricant are recommended - as it's upside down watch out for falling swarf, yuk !

DON'T be tempted to use an Ezi-out extractor or similar. These only work when the thread is easy to turn but there's nothing to grip, a situation which I have never encountered ! If you try using them on the usual well siezed fastener, they expand the remains and make them even tighter, or worse still they snap off and the hardened extractor is near impossible to remove.

Good Luck !

 

[Threesheded]

Hi Anthony,


Thanks for the reply, your summation of the problem is correct, the bumpstops are probably spun up by hand in the factory and approximately half the thread portudes above the captive nut (a rough guess just by inserting a finger into the channel between the top of the mount and the chassis rail in which it sits). No space to get a wire brush in there. I have had to drill out bolts on a previous vehicle and agree it is a tedious job, however the suspension leaf hinders access a little and would need to be removed. I totally agree with you about easy outs as I once had one of these break off in a bolt in one of my motorbikes and that was a nightmare. I have ordered the attached set of rounded bolt extractors off the internet as a punt since some people have had success with these.

With regards to the rust the bumpstops only have a very light coating of zinc (I would guess) and this does not seem up the rigours of living under a van used on the roads all year round, there is no protective coating applied to the mounting studs leading to fun and games at replacement time!

Cheers

Ed

 

[Threesheded]

Hi All,
After my last post I sprayed a bit more penetrating oil into the cavity where the mounting points are. I remembered in the dim and distant past some one had bought me a universal socket with spring loaded pins. After trawling through the midden that is my garage I found the socket and offered it up to the offending stud which was more of an oval head after yesterdays efforts. To my surprise it gained purchase so my first move was to turn the socket so that the bolt was going back from where it had come, so that I could hopefully allow some of the crud to clear and spray a bit more penetrating oil onto the exposed threads before continuing with removal. Imagine my delight and choice of expletives when the captive nut in the chassis broke away with the slightest provocation..
At least the way forward was now clear, so out with the padsaw and saw in between the top of the mount and chassis to remove the offending article.
On removal of the captive cage for the bumpstop it is clear that the centre hole in the cage is hexagonal and the base of the stud is also hexagonal but there is very little evidence of bonding between the two.

The captive nut image attached has three of the smallest dabs of weld I have ever seen and little evidence of penetration on the underside, but to be fair its only function is to locate the top of the bumpstop so it is not really stressed (unless you try and remove the bumpstop after a few years of road use).
The hole in the chassis, freshly vacated, is 13.1mm so ideal for a M10 rivnut.

The steel rivnuts I have are M10 x 1.5 as opposed to the M10 x 1.25 of the supplied bolts for the air suspension kit, I have same grade of bolt in M10 by 1.5 and since I dont intend removing the air suspension I will be fitting these. I am aware that the finer metric thread prevents backing off of the bolt, but since the head is held captive in the mount of the air suspension and the bellows and top arrangement is spun up by hand I cant see any issues. I will cut a clearance hole for the shoulder of the rivnut in the platic top of the air suspension mount.

I had a bench test of setting the two types of steel rivnuts I have using the spanner and nut method and am happy this is achievable in the space available, the hexagonal rivnut is a better fit in the hole prior to tightening up so I would hope achieves a better centreing and appears to achieve a better spread when compressed so I will probably use this one. The other rivnut has a knurled surface but I am not sure how effective this would be in gripping the painted (I would hope) surface it is squashed onto.

Fitting the rivnuts is tomorrows job.

 

[Anthony489]

Hi again

I admire your perseverance, and glad you seem to be on the way to a solution.

I would be interested to know what you think of the semi-air setup once it's up and running. The factory fit extended bumpstop/spring assister seems like a rather crude device which is not well suited to vehicles like motorhomes which are always near their top limit for loading.

 

[RS3100]

I have Dunlop semi-are rear suspension on my PVC motorhome, for ride comfort rather than to overcome any loading problems. It transforms the handling and ride remarkably. Much less jarring and jolting at the rear end and the buffering windsteer effect when passing or being passed by HGVs on motorways and dual carriageways is almost completely eliminated. I find it only needs to be inflated to around 15-20 psi to restore the original ride-height on my van.

 

[Anthony489]

Hi RS3100

I am interested in your experience with the semi-air. Our motorhome is a PVC and when laden is usually around 3250 kg. Even unladen at around 2900 kg the bump stops are in contact with the axle. Looking at empty panel vans in the local showroom (killing time whilst the MOT is done) I notice there is usually about 20 mm clearance.


Our dog always comes with us on our travels. Her comfy padded bed is right at the rear, but as soon as we start moving she always walks up to the front and settles down on the hard floor just behind the passenger seat.

At first I didn't understand why she did this, but then one day I tried riding in the rear whilst seeking the source of yet another rattle. The ride quality there is much worse than in the front seats so she is voting with her feet !

 

[RS3100]

Anthony489 my van sometimes runs close to its 3500kg limit, as I travel with a full water tank if we aren't using sites. My only real issue with the standard van suspension was that it was quite harsh, as your dog appears to have noticed! But having fitted the semi-air, as well as making the suspension action more progressive, it also reduced body roll on cornering and improved stability in cross winds and when passing large vehicles, as mentioned.

The "bump-stop" cones on the standard suspension are actually called spring assisters by Fiat, and are intended to make contact with the springs in all but the most lightly laden conditions, and compress under loading to a degree unlike normal bump stops that restrict the end of travel. So on a motorhome where the furniture and other onboard equipment amounts to a payload before any other items are added, in practice they will always be in contact with the springs, which adds to the firmness and limited travel of the suspension at the rear. The attached photo is of a newly converted van identical to mine, unladen apart from the conversion itself, and although you can't actually see the point where the spring assister cone and the spring meet, because of the handbrake cable, I can assure you that they were in contact. And that is on a van with the optional twin leaf springs, which you can see are not loaded sufficiently for the helper spring to be fully in contact!

My only surprise was just how little pressure was needed in the airbags, but the Dunlop bags have a larger volume than some of the other kits I've seen, which no doubt helps the suspension to feel more progressive, plus of course a PVC has no real rear end overhang acting on the rear axle loading unlike many coachbuilt vans.

As I said, I had no real need for the semi-air from the point of raising the ride height or otherwise countering excessive loading, but just from the improvements they make to the general feel and handling of the van,I would highly recommend them.

 

[Threesheded]

Hi All,
Finally got round to fitting the rivnut in the mounting hole today, but since I had been using the same bolt for my bench testing yesterday, as a precaution, I decided to get a new bolt for setting the rivnut, knowing my luck the old one would have snapped half way through. The only problem was that Screwfix only sell them in 50s so I now have 49 excess bolts.
I gave the mounting plate on the van a couple of coats of stonechip, and started to set the rivnut. What was easy on the bench was more difficult in the confined area under the van and the washers kep binding onto the nut and unscrewing the bolt even when oil was used to lubricate things. Luckily I had ,many years ago, ordered a 10mm thrust bearing off one of the chinese websites, inserting this between the washers along with a little oil and the insert snugged up no problem. As usual looking for the thrust bearing I had seen a few weeks previously sucked up almost two hours of my time! probably to do with my age. Before anyone mentions the correct tool I do have a proper rivnut setter, but (apart from twice) almost every time I have needed to set rivnuts in the past there is no room to get the handles closed.

You can see from the photo that the plate that carried the nut is fairly thin but centres the bumpstop/airbag on the chassis rail either sided of the swedged area. I had opened the area on the top of the airbag to accept the collar of the rivnut, but I would imagine the airbag would have pressed it in any way.

Airbag now installed (with copperslip on the threads ) and the airlines should get plumbed in tomorrow.
If I was buying a NEW Ducato, I would definitely get it up on the stands and slack down the bumpstops slap some copperslip on them and reinstall them, because even if you are not installing airbags they will need replacing at some time, certainly on a PVC that is run close to its limits weight wise.

With regards to the ride with bumpstops it was always harsh and crashy especially when going over the local level crossing where I live. Even when the van was empty of water the bumpstops were always sitting on the springs. Even with no pressure currently in the airbags the ride height already appears to be a couple inches higher at the rear, going by the way the wheel sits in the wheel arch.
Thanks for the help and encouragement.
I will let you know how the new kit performs when I get it installed.

Cheers

 

[Threesheded]

Hi All

The remainder of the installation process was easy enough, routing of the airlines was straightforward. I took them into the cab area using the rubber sealing plug under the handbrake void. The airlines were protected using flexible trunking from screwfix, and secured along the chassis rails and sundry brackets. I have the excess airline looped under the van and in the footwell. I took the 12v for the onboard compressor from the convertors socket in the drivers side B pillar and managed to get the compressor tucked in under the drivers footwell cover.

After experimenting with the settings over 400 miles or so I find that 2bar is about right. The air bags have certainly silenced the racket coming from the back of the van, deep potholes and railway crossings will still cause me to hunch my shoulders grind my teeth but nowhere near as bad as before. Ride height at the rear is much improved. The only slightly disconcerting thing is watching the gauges flickering as the van makes its way down the road and the suspension starts to work.
Despite my setbacks during bumpstop removal I find the airbags to be a worthwhile improvement.
Next project is replacing the leaky power steering rack but I think I will leave that to the professionals.

 

[slowpace]

is itthe leaky power steering rack or the 2 pipes if pipes these are the people fpr pipes this was what i had to get Fiat Ducato Steering Rack Pipes (1996-2006) PSSRTP0111£36.00£36.00

Hi All

The remainder of the installation process was easy enough, routing of the airlines was straightforward. I took them into the cab area using the rubber sealing plug under the handbrake void. The airlines were protected using flexible trunking from screwfix, and secured along the chassis rails and sundry brackets. I have the excess airline looped under the van and in the footwell. I took the 12v for the onboard compressor from the convertors socket in the drivers side B pillar and managed to get the compressor tucked in under the drivers footwell cover.

After experimenting with the settings over 400 miles or so I find that 2bar is about right. The air bags have certainly silenced the racket coming from the back of the van, deep potholes and railway crossings will still cause me to hunch my shoulders grind my teeth but nowhere near as bad as before. Ride height at the rear is much improved. The only slightly disconcerting thing is watching the gauges flickering as the van makes its way down the road and the suspension starts to work.
Despite my setbacks during bumpstop removal I find the airbags to be a worthwhile improvement.
Next project is replacing the leaky power steering rack but I think I will leave that to the professionals.

 

[Threesheded]

Slowpace thanks for the info. Unfortunately the seal on offside of the steering rack had gone and it was only the boot that was retaining the fluid. For access I would have need a four post lift to raise the van so had to get a local garage to do it at the same time as the MOT. The MOT also led to the discovery of a cracked spring on the front suspension which required replacement so all in all an expensive day out for the van.

 

[Glenn68]

Hi threesheded, thanks for all your information although very disconcerting regarding the bump stop removal. I am thinking of fitting an air stop system to my 56 plate ducato coach built motorhome. Due in part to the bump/pot hole grimace shrug twitch I have also developed. I have one question regarding the system. Does it need to be connected to a compressor or can you manually pressurise the system as and when required.
Many thanks in advance for your assistance
Regards Glenn