Bouncy 230TE

[MIKE236]

G'dday Fellow Benzians

Been away for a long time and left the car in relatives care to be tended to. However, found out that the rear shocks have worn out due to heavy loads been left in the car for long periods. :evil: The prob now is that after replacing with OEM self levelling shocks, the car now rides like a RODEO bouncing hyde-ho after running over anything that is isn't smooth . Local indy thinks that it might be the accumulator spheres that is shot but not 100% confident that it is the problem.

What I have noticed at the moment is that the car will self-level after a heavy load is inserted thus ruling out the spheres or am I wrong.

Need advice and help badly as the bouncing is driving me nuts :lol:
Andy or other 230TE experts....any suggestions :?:

Thanks again guys for all help rendered.

 

[teky]

sounds like the shockers need changeing

 

[NormanB]

Mike - it sounds like the spheres have gone. They are renowned for it and the symptoms fit. I have never done it but understand they are easy DIY and accessible via the load space - up carpets! (I think they are around £50 a side).

Good luck, let us know how you get on.

 

[MIKE236]

Thanks guys for the input.

Teky: I just had it changed with similar specs as the ori ones. Are there different types of self levelling shocks for this model? The indy guy claimed that there is only one type or did he installed the wrong one.

Norm: Thanks for that. Reading through the benz DIY manual, it mentions that if the spheres are KAPUT, then the car will not self level. However, after testing with loads up to 200kg, it stills self level.

Interesting note which I forgot to mention was that with a heavy rear load, the bounciness decreases markedly and rides like normal. But I think driving around town with a 200kg load just to mask the bouncy feeling is just too much. Anyway will have a look see again tomorrow with the indy regarding the spheres and shocks. Otherwise its back to the dealers :evil:

Thanks again and will keep you posted on the outcome. Cheers

 

[TimN]

You seem to be incredibly unlucky. I have had a rear shock absorber fail an MOT test before. It had quite clearly failed as hydraulic oil could be seen leaking from the seal. I'll bet the shocks didn't come cheep. Faced with this sort of problem many owners strip out the self levelling system and swap it for second hand saloon parts.

You haven't mensioned whether the vehicle was in regular use whilst it was in the care of others. If it wasn't then you would expect the rear of the car to sink over a period of time with a load in as the rubber o-ring in the self levelling valve will be worn and will allow fluid to filter past.

I understand that it is a gas pocket inside the spheres that absobs the bumps. Could be worth bleeding before spending more money although in theory if the shocks have been replavced then this has already been done?

 

[flyingtech55]

Hi

I don't know about self-leveling Mercs. but before I bought my 190E I owned (and maintained) an excellent Citroen BX which as you probably know has hydraulic suspension with self levelling at the rear.

It works as follows:

An engine driven hydraulic pump sends high pressure oil through a manifold to what look like shock absorbers (but are in fact hydraulic rams)and struts via 2 way valves. The valves are mounted basically between the axles and the body. When the car is down the valves are opened to the HP oil which fills the struts/shockers. This makes the car rise. When the car is at the correct height, the comparative height between the axle and the body closes the valves and the HP oil is trapped in the struts/shockers. If the car gets too high, such as by unloading the boot, the valve opens the other way and lets some HP oil oil escape back to the reservour and the car sinks until it regains its correct ride height. The valve then closes again trapping the HP oil. If that was all there was to it however the car would ride as hard as a rock and bounce about all over the place so spheres are incorporated into the system. Each strut/shocker unit has a sphere associated with it. The spheres contain a rubber diaphram inside it dividing it into two chambers. One chamber contains nitrogen gas at a pressure of about 3000 psi. The other chamber, the one that screws onto the strut is open to the HP oil trapped in the strut. The oil passes through a very small hole into the sphere. In this way the compressed nitrogen gas provides the spring and damper action. There is also a fifth sphere called the accumulator next to the oil pump to ease the load on the pump and to provide (in the case of the Citroen) a safety reserve for the brakes.

The faults you get with this are:

The seals go in the struts and rams. This causes hydraulic oil leaks. In the Citroen these will blow the return pipes off and cause sometimes spectacular amounts of oil to run out.

Blocked or faulty height valves. This causes various symptoms such as the car runs at the wrong ride height or is slow to rise or to slowly sink down usually at the back while standing at traffic lights or junctions.

Worn out spheres. Because of the pressure, the rubber is slightly permiable to the nitrogen gas and it very slowly leaks out. The gas pocket gets smaller and smaller and the ride gets harder and harder over a period of time. If you don't change the spheres the car can get quite dangerous because it bounces about so much over bumps and such.

On the Citroen you are advised to change the accumulator sphere every two years, the front spheres every three years and the rear spheres every five years. My car was about three years old when I got it and as far as I know the spheres had never been changed. When I did change them to difference in the ride was really noticeable.

As I say I don't know if this is the way the back end of the Merc. works but it may be a good starting point and is based on practical experience of the Citroen.

Gliderman

 

[teky]

citroen do make very good suspention indeed and other use it within there kits but the citroen dosnt have shockers and springs like the merc its a stand alone hydrolic system on the bx as are most of the citroens, i have worked on many and know exactly what you mean :wink:

 

[NormanB]

But his point about the spheres is bang on and applies to the Merc too!

 

[teky]

very possible but the way i read the #1 post the suspention is bouncy meaning hard bouncy the shocks could cause that also and an easy test would be is after its been stood for a while and the self level has lost its pressure try bounceing the rear of the car this will rule out at least one of them if its hard then the shocks

 

[MIKE236]

Gliderman, thanks for the detailed explanation regarding the self levelling system. After reading your post it is very likely that the spheres are shot. Thanks to you and norman for that. Why I say this is so because the ride is very hard and bounces like a trampoline over bumps :!: There are no leaks present which indicates worn-out rubber seals.

Tim you are right the shocks cost a small fortune each not inclusive of labour. Like you mentioned a friend had his system stripped to the saloon version to avoid these hassles, thus he has no experience whatsoever in maintaining the self-levelling. However, I believe the system was superbly designed and no reason to change it. If not for the rodeo-like effect, it is the most dependable car I have ever driven.

Another question, what do you reckon, should I preventively replace all the rubber o-ring seals while installing the spheres eventhough these are not leaking any hydraulic fluid?

Thanks again for all your help and knowledge. Cheers.

 

[TimN]

I didn't know that there were any orings on the spheres. I have replaced the flexible hose from the sphere to a shock because the metal part at the top is liable to sheering. The new hose was simlply tapered at the end, just like a brake hose, to provide the seal.

Have a look at your spring condition. They have a tenaency to break off the end inside the well of the trailing arm. I had one once with a number of breaks. If your spring is getting smaller but the self levelling system is trying to maintain the same ride height I suppose it would result in some interesting ride qualities.

 

[flyingtech55]

Bouncy ride 230TE

Hi Tim and Mike

Based only on my knowledge of the Citroen, the replacement spheres came supplied with new o-ring seals. It was essential that the o-rings where renewed with the new spheres otherwise hydraulic leaks resulted between the sphere and the bit it screwed onto. You had to be careful how you fitted them because you could twist them in their groove if you weren't careful.

Incidently, I used to buy my spheres from a company called Plieades in Cambridge. They charged £25 per sphere (exchange) but they refunded £10 per sphere if it could be recharged satisfactorily. I replaced mine every two years and I always got the refund and retained the 'magic carpet' ride you get from Citroens. By comparison, Citroen stealerships used to charge £60 per sphere which would mean £300 per car set as against £75 (+P&P) every two years.

Again, I don't know how much of this applies to Mercedes spheres but why not ring Pleiades and ask them if they do spheres for Mercs. They do ones for Rolls Royces. Their 'phone no. is 01487 831239. I always found them very helpful when I had the BX. I would still be driving it if some idiot hadn't driven into the back of it and totalled it.

Gliderman

 

[MIKE236]

Thanks Gliderman and Tim for that input.

Been scouting around for the spheres as the local indy and spares do not stock them as they seldom or have never replaced one for the mercs. They say that the spheres should last for ever with proper care..saying this with a grin meaning which I have thrashed mine and deserve this debacle.

Had tested teky's idea of testing the shocks when engine off and there's very minimal bounce like what you aspect of a normal suspension. But once engine up and running the bounciness becomes very marked. Therefore the indy concluded that the spheres or whatever valves which should control the hydraulic fluid isn't functioning properly. Also tested with a full load and to my surprise, the fluid reservoir filled up to the brim to the point of overflowing.

Tim: also had a look at the springs the first time around but there weren't any cracks or breakages but I have procured new ones to be replaced when the new speheres are installed.

BTW, just and afterthought, will citroen spheres fit into the mercs?

Thanks guys and will report on outcome once the little widgets are installed. :x Cheers

 

[Peter Guenther]

Bouncy

Symtoms of bad spheres, rear shocks are not "shocks" but hydraulic struts. They rarely go bad, and usually leak at the seals. The spheres are gas filled a with a diaphram separating the oil/ gas. The diaphram ruptures, The replacement at the dealer is about $380 US, independent shops should charge less. The spheres are $100 ea. , you can do the job yourself. It is messy when you loosen the fittings since oil has gotten into the sphere, and best done with the car in the air, purge the system by disconnecting the lever and manually cycling the valve. Alaways use the proper MB fluid, dont reuse the old
The rear struts are $450 ea

 

[buckljli]

Mike, best life out of a hydraulic accumulator is 10 years.
After this the diaphragm has allowed all the gas above it to permeate through the diaphragm into the hydraulic fluid and escape. This means that now the hydraulic fluid can push the diaphragm up inside the sphere till it touches the top and it does this at a very low pressure. That means that there is no elasticity in the hydraulic system apart from whats in the pipework (small) Thats why the supension goes so hard when the gas has escaped.

In the uk there used to be companies who would "recharge" the gas (usually nitrogen) to a specific pressure.

:- Change your spheres/accumulators!
Jules

 

[MIKE236]

Thanks guys for that info.

Mind already set on changing the spheres but alas most parts retailers do not stock them here down under. Got hold of Eurocarparts on the internet and will be sending them by courier next week!!

Guess have to bear with it for a while.

Thanks again all. Cheers and have a nice weekend

 

[MIKE236]

Hi guys.

Promised to give feedback on the problem I had. It was definitely the spheres and boy were they shot to hell. Gas completely empty and diaphragm looks like it has been bitten of by the dogs. Changed most of the seals and pipes ( want to keep it going for another 10 years!) and finally I have perfect comfort as what a benz should ride like. The downside is that those little buggers cost a fortune to install :evil:

To those who pointed out to the possible problem many thanks. Goes to show what a nitwit I am in diagnosing a car which I have used for umpteen years. Still haven't got the knack to DIY though. Still trying very hard with very poor results.

Thanks again and cheers to all