I am considering a white 1984 300SD with 338K for $2399. Interior and body are in excellent condition and it is 100% rust free.
The possible problem that has me concerned is the severe shake the engine has at idle. It will actually shake the entire car. Just the slightest acceleration- the engine will smooth out as smooth as silk. Its only at idle when it does it. It has 338K and the seller stopped driving it last summer because the A/C went out. It has been in the garage for a few months. He said it was not doing it before and it may need a "tune-up". He has owned it since 1989 when it had 80K and has performed regular service. I know nothing about Mercedes. Could this be something as simple as a tune-up, or is it something major? My dad said it sounded like an injector is going bad. I really like this car, as it is in excellent condition and if it is nothing major- I will probably buy it if it is nothing severe. I am supposed to go back tomorrow in the daylight and drive it down the road at least. I wanted to check here first to check on this engine problem before I bought it. BTW- he is asking $2399 for the car, but I think I can get it for less than that.
On the other Mercedes site- I have heard it could be any of the following: Bad/clogged injectors, fuel distributor pump, water in/contaminated fuel, motor mount/motor shocks, rack dampening bolt, injector pump, to as severe as bad compression. The slightest acceleration- the car runs very smoothly.
I was going to have the compression checked, but the cars plates and stickers has expired and I cannot drive it far. My uncle said I should get a compression check before I buy it. Would it still run smoothly upon acceleration if it was bad compression? Any input as to what the problem could be? If it is bad compression- about how much $$ to have it repaired?

ANY advice/information greatly appreciated.

 

Many diesel's have a slight shake at idle, however the MB's usualy are pretty smooth. My question to you is what do you expect for that amount of money and with a vehicle that is just about 20 years old?? You most likely if you purchase it will be its last owner. This shake as you describe it could be a valve leaking, poor compression due to rings, a bad injector, etc. To accuratly diagnose and repair this problem could cost almost as much or more than you are paying for the car. Doubt if the present owner stopped driving it just due to the A/C.

 

I have (had) three 83 & 84 W123 diesels. Two were 3L turbo-diesels with the same engine in the car you are looking at. Shaking at idle is one thing that is inherant in that engine. Some shake more than others. Both my 300D & 300TD went over 200K miles, and are still going strong. My 300D I lent to my father and he spent money trying to have the shaking smoothed out without success.

When my 300D was new and still under Warranty, an MB technition explained that the "lamba" adjustment in the fuel rack can smooth out some shake, but not in all 300's. His only "good" solution was to replace the fuel rack, but MB didn't consider it a defect so they would not do it under warranty.

My ony other suggestion is to check to make sure the valves are adjusted properly. Pulling off the vave cover and adjusting the valves, is about the only servicing (other than repalcing filters or glow plugs) that needs to be done on these engines. I am not sure if valve adjustment affect the vibration or not, but it still needs to be done every 30K miles.

Check to make sure the oil was replaced every 5,000 miles as diesels put sulfuic acid into the oil that needs to be removed. Also the transmission needs a filter change and filter change every 30,000 miles.

Good Luck.

<sph17>

 

bumping up the idle speed a tad sometimes help smooth out the shake, especailly if it is too slow to begin with. Doing it is not a big deal, you only need two open end wrenches to back off two nuts that are clinched together, and a screw driver to turn a nut, on the drivers side of the engine near where the emergency shut off mechanium is.

<sph17>

 

actually my ex-GF has the exact same car with 284K on it (when th espeedo stopped 5 years ago)... we solved it AFTER trying the tune up and other suggested items, there was a faulty engine mount. I cant remember for the life of me which one. but its smooth as glass now.