I've called a guy about an '84 td advertised. He wasn't home and will not be until next week so when I talk to him I want to be armed with questions. It has 282k KM (~175k mi) on it and I'm wondering what if any are common items that will fail at around that mileage (or less), where the rust grows on these cars....

Thanks

I recently purchased a 300TD, so I'll tell you a few things I looked for when I was hunting..

One common failure on these cars is the self leveling rear suspension. There is a pump on the front of the engine block, a fluid tank under the hood on the left side, and two steel lines running back (they look like brake lines, and run under the center of the car). The lines go to a valve that is connected to the sway bar, and each rear wheel has a strut, and an accumulator (aka nitrogen sphere). The strut lifts up and down, raising and lowering the rear of the car, and the nitrogen sphere is your 'shock absorber' that compresses and expands to absorb bumps. Leaking lines are common, and can mask other problems. Inspect the lines, and if you see any 'repairs' preformed, assume the line will need to be replaced, they are high pressure hydraulic lines and you can't just hose-clamp them together as is a common 'fix'. The struts usually last a long time, but check their seals for leaking. Accumulators usually go out at around 50k, and are easy to identify in a test drive. If the car feels like it has no rear shocks at all (very harsh) then the accumulators are bad. They are cheap, only about 100$ each and an easy replacement, but keep that cost in mind.

You can also test the whole system, have a few heavy people sit in the back of the car, and turn on the engine, you should see it lift a bit as it levels the weight. If the car looks like its dragging its butt, be extra vigilant about that rear suspension.

Check the fluid level for the rear suspension, if the tank is empty, or veery low, be wary, because there may be leaks that would indicate a line replacement (not too bad), valve replacement (a little worse), strut replacement (expensive), or pump replacement (yikes). You don't want to run the system empty, because the pump is lubricated by the hydraulic fluid, so even if a part is leaking, it pays to keep it topped up, even with expensive fluid, just to keep the 600$ pump from failing until you can fix the leak.

However, if the rear suspension works right, it is quite durable, and very nice, it gives the car a very confident ride, even when heavily loaded. I'm glad mine is there.

Common rust places are wheel wells and floor pans. I like to check underneath the spare tire! My 300TD has some not-to-great rust there, it wasn't enough for me to not buy the car, but its definately something I'll need to fix this spring before it gets worse. But its by far the rustiest part of the car, so I'm not too concerned.

If your jack points have anything more than surface rust, stay away. If they have surface rust, be veery vigilant, because there may be hidden body rot.

Aside from that, do some searches here, and you'll find a lot of great advice about things to look for when shopping for a w123. Most issues common to sedans are also common to wagons, with the major exception of the self leveling suspension.

Good luck, and remember not to get emotionally attached too soon. For every good car you see for sale, there is a great car waiting for a home, so always make yourself mentally ready to say, "no", because another opprotunity will always come around. I shopped for many months, and ended up with a great 300TD for a great price, though there were a few I was very tempted to buy, and now are glad I passed up. Its easier to pay a little more at the beginning and get a good car you can maintain, than to save a few bucks and get a car that will nickle and dime you to death. "There is nothing more expensive than a cheap Mercedes..."

I hope you find the right one soon, or that this one you are checking out is the right one. They are definately great cars.

Peace,
Sam

__________________
"That f***in' biodiesel is makin' me hungry."

1982 300TD Astral Silver w/ 250k (BIO BNZ)
2001 Aprilia SR50 Corsa Red w/ 5.5k (>100 MPG)