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W123 HELPLINE Article first published in January 1999 |
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A Happy New Year to all our W123 owners. I'm glad to report a great many of you took the trouble to write to and phone me with much gratitude and encouragement, for last issue's feature on rust and water leak problems. I take back what I said about Wales as many of you, all over the UK, have experienced even more water leakage problems than me! Beware imitations Many of you enquired about the cost of body panel repairs, especially as there are numerous 'pattern' panels available for the W123 at a fraction of the cost of genuine MB parts. All I can advise on this is that my own experience of fitting non-original panels has not been good - all the ones I have tried to fit, and seen fitted by numerous other owners, do not have the correct profile and generally are difficult to align. The quality is also poor, but as they are so cheap I can quite understand why they are fitted to cars which are in poor condition and do not warrant the outlay on original parts. If your W123 is anywhere near 'good condition' steer well clear of non-Mercedes panels. Just compare the prices - a genuine MB front wing is £250,00, a pattern wing can be as little as £20.00! Remember the old adage "you get what you pay for". Not only panels, but I have also received numerous calls regarding electrical parts - points, leads, coils etc supplied by factors - also expiring early and not performing correctly. Shock absorbers seem to be OK as they are made by the original manufacturers, but be careful to check that the serial numbers match exactly. Now on to this month's feature. T-series rear suspension Launched slightly later than the saloons, the T-series vehicles were Mercedes-Benz' first in-house estate car. Built at a new facility in Bremen, as usual they set a standard for excellence that other manufacturers measured their vehicles against. The main distinguishing mechanical feature of these vehicles is their self- leveling rear suspension. This was nothing new to Daimler-Benz as it had been fitted to the luxurious 600 and 300-series cars since the early 60s, but on the new estate cars a new hydraulic oil pressure system was designed instead of the horrendously expensive compressed air system of the earlier vehicles. The new system, although simple to understand, is technically quite complex. An engine driven pump drives hydraulic fluid to a level control valve unit mounted under the rear axle. This unit has a small bracket attached to the rear torsion bar. When the car is compressed by the weight of two or more adults the torsion bar sinks and the bracket attached to the control unit is moved, allowing more fluid to enter the rear shock absorbers and increasing the ride height to compensate for the additional weight. A ball shaped pressure reservoir is also attached to each rear shock absorber, filled with a compressed gas. |
The oil circulates to a reservoir in the engine bay. Generally the system is extremely reliable and does not require a great deal of maintenance. Sadly it is when they have had no maintenance at all that things start to go wrong. The most common fault is - rear of car not self-leveling. Quite often this is because the self- leveling valve unit is stuck in one position due to lack of maintenance. To check if yours is working place the car on a lift and detach the connecting bracket from the torsion bar, run the engine and gently push the control arm up or down and the vehicle will rise and fall slowly. Liberal cleaning of the unit and soaking with WD40will usually free the bracket up. Re- connect the bracket at exactly the same place. Other reasons for failure to self-level are incorrect pressure in the system (pump failure) or a faulty unit (0 ring failure in sealed unit) or leak of fluid or gas from the pressure reservoir. All the above need specialist equipment to test and diagnose, I do not recommend you attempt it at home. Quite often the vehicle will drive quite well but may be too high or low. The system is very quiet in operation and also very smooth, any clicking over bumps or undulations is usually the torsion bar connectors which are mounted on the ends of the bar and are white plastic and are quite easily replaced and not expensive. I have also been informed that the pump bearing seal can fail on the engine, causing engine oil to be sucked into the hydraulic fluid reservoir. This will cause the reservoir to overflow and allow the fluid to become discoloured with dirty engine oil. If you discover this you must not use your car, as all the oil can be sucked out of the engine, with obvious catastrophic results. Normally the fluid stays at the same level in the reservoir and never goes back. I have included some technical illustrations for you to get a basic understanding of the system, but I must stress again, if you have serious faults with the system, get it checked with the correct pressure gauges etc by a MB trained technician. It is not a job for any garage, and no it's not the same as a Citroen! Finally costs; the system is superbly engineered and of the highest quality, consequently it is expensive. I do not have the up to date prices at the moment but can tell you the rear shock absorbers are nearly £200.00 each and the self-leveling valve is over £250.00 Second-hand items are not easy to find, and obviously may not be in A1 order, as the vast majority of these super stylish estates have done huge mileages by now. I'm often asked, do I know of a good condition, low mileage T-series W123 and sadly I have to answer, "there is gold in the mountains here in Wales, and I think I have a better chance of finding it than a low mileage T-series!" These cars were made for driving - "T" stands for touring after all.
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