300TD hydraulics - springs bad?
 

1985 300TD wagon - with no (self levelling) hydraulic pressure - rear sits VERY LOW. Are springs bad (130K miles) Thanks Steve.
Adjustment rod from torsion bar to valve is adjusted to its MINIMUM length. I have a feeling this is bad? Thanks

Hello, Steve.

I have the same car as you, and I like it.

I don't know much about this - there is another post from another guy with a similar problem, and he got several responses that you might find helpful. Do a search on "300 TD* Turbo*" and I think you will find it - that's how I found it.

My hydraulic oil is low, but I think my system is still working fine.

Do you know what kind of hydraulic oil is recommended for this car? I want to buy some, but I don't know what/where to get it.

Clarke

The TD rear suspension is one that uses both the springs and the hyd unit to support the car. If one system is not working fully then the other has to do a lot more work... and wears out faster.. and springs only have a certain lifespan even just sitting still.. if the weight of the car is on them.... but in use you can figure 50,000-75,000 miles before the steel springs should be either replaced or rearched.... I know tons of people will howl at that.. but I am going from what car manufacturers used to list as the life of coil springs..
There are also stronger springs available from MB for rough roads. I have never seen a car which did not benifit from new springs...

There is a special fuid just for the suspension system. You could try Fastlane. I have seen it in the Performance Products catalog. It is not cheap.
I don't think the problem is necessarily springs. It is probably sitting low because of the problem in the hydraulic system. Get that fixed first before doing anything to the springs.

Not necessarily.

Accumulators that have failed or have lost some pressure will produce similar symptoms.

If the system reservoir is properly filled and there are no apparent hydraulic leaks anywhere, the problem is either an actuating valve problem, an adjustment issue or failed accumulators.

My Kombi has the nasty habit of periodically loosening the actuating arm from the rod it connects to...this will also cause a squat.

One more thing...
Do not attempt to remove the springs on theses vehicles with a cheapo, clamp on the outside, $7.50 "buy-it-now" on eBay, spring compressor. The ONLY safe way to perform a springectomy is with either the "Sir Tools" or "Klann" internal spring compressor made for MBZ springs. It takes about 1000# of force to sufficiently compress these springs so that they can be removed from the trailing arm. At that point there is sufficient energy stored in one of those springs to kill you if it gets loose.

Be careful.

Another thing...
You should also do a search in the diesel forum on "SLS", "hydropneumatic" and/or "wagon rear suspension"...plenty has been written in here on this subject.

if you dont have leaks, get under the rear of the car near center of the rear axel area. look for a small 3x3 box . it will have a lever coming out of it that has 2 or 3 articulation ponts which then attaches to a rod running parallel to the axel. it is attached to the rod by a u clamp. this may have come loose. if it has you will not get any rise out of the hydro system . the easiest way to check is to put car on ramps(rear end) then loosen the clamp from the rod. with the car running move the rod up& down the car should raise & lower with the rod moving. obviously you need to take normal saftey steps. be sure you are lying flat when moving the rod as there is substantial up/down movement with the rod movement if the system is working. if this does not work the i have no more help .

john m

The levelling valve (little silver box) by the diff can be rebuilt with a rebuild kit from the dealer. It's probably wise to replace the hyd. spheres and flush the system too. Don't forget to renew the filter in the resevoir, those almost never get replaced.

Fantastic! Thanks for all the information. If springs are bad enough, can they cause immediate damage to new accumulators? I replaced them 1 month ago - the suspension seems too firm - when I step on rear bumper - it doesnt rock - but rather only deflects downward maybe 2 to 3 inches. I read in the manual that if car is not at proper level (in driving ready condition) that the hydraulics should not be used to raise to proper height -assuming that lever is properly adjusted, not loose etc.,. By doing so - the hydraulics will require more pressure than normal and damage may result to hydraulic system. Is it possible to destroy brand new accumulators immediately due to this higher pressure? Steve
PS The leak I have on drivers side does not run down shaft of strut - rather it is all over spring. Could it be a leak from a loose hyd hose connection as this is up above the top of the spring? I am in the process of accessing tops of struts from carpet cover above - havent gotten in there yet? Do these hose connections come loose often?

It is unlikely you have damaged your new accumulators. The pressure is largely a function of engine RPM, not the length of time it is on. The accumulators should be able to take it unless the springs are well and truly gone so the hydraulics is doing all the work all the time. The system is designed, after all, to assist the springs under heavy loads.

It's possible you have a leaking hose or fitting but I've never heard of the fittings coming loose on their own so I'd suspect a bad hose if that's the source of the leak. By the way, always use a flare wrench on the fittings as they strip easily (I believe they are made of brass).