Read these guides:
http://mbdieseldiy.tripod.com/dog.htm
http://mercedes-w123.net/buyers_guide.htm

A minor point, but I always take a look at the antenna grommet. The original one on a 20 year old car is guaranteed to be bad. If it has been replaced, the car must have been maintained, if not, the trunk has probably been wet for years.

I've got a lot of respect for you Richard, and only busted on you based on your history of a good sense of humor. I hope you took it in the light-hearted manner in which it was intended......;)

Rust never sleeps
 

While your looking underneath for rust, cracked boots, oil leaks ect., look at the condition of the exhaust. Not a cheap system on these cars.

Comedian
 

Of course I did, I mean I must be the biggest joker or comedian around here. I'm not uptight and stressed out like Brian Carlton :D :D :D :D .I am flattered that you even thought you had to apologize~!

The dreaded part-- Engine Assessment
 

I'm still thinking about how to write this without making it overly expensive or time consuming. Also a lot of engine asessment has to do with Injection Pump assessment. Finally since the price of these cars is around the $1K mark, I doubt anyone wants to pay someone $100 to have it checked out and have a compression check done. Most buyers are probably shooting from the Hip and going by gut feelings.
Sadly a lot of these cars don't get well maintained towards the end of their use. If it has been, I am sure you will know that intuitively by the owner's presentation of the car. He will be usually knowledgable and probably have another Diesel.

I would just hate to see a buyer burned by bad oil rings or serious engine damage. To that extent I would recommend driving it for at least 40 to 60 miles and checking the oil level before and after. Also though a diesel is noisy, a good diesel's noise is rythmic and periodic and doesn't have irregular sounds.

I am going to give some thought to this this weekend.

OK, I'll throw one in here by quoting myself from another thread:

I have yet to drive an old MB w/ recirc steering that felt 'tight' in the center.

I have seen some turbo models w/ generic setups...or 'pipes' that didn't make more noise than stock.

Purchasing A Diesel Benz
 

I posted a major check list a few months ago that centered around the engine only. If anyone desires this list, contact me at: alfredburn@hotmail.com

I would say that having mechanical ability is a great asset that will save owners a bundle. I believe that everyone desiring to work on their benz should go to a technical school and sign up for some courses (one or two at a time). Doing so will give you mechanical understanding and courage to tackle your repairs with confidence. I have an acronym that I wholeheartedly believe. It is called "TEKC".

T - Training
E - Experience
K - Knowledge about the job you are getting ready to undertake
C - Confidence that you can perform it

These diesel benz are fun to work on and give you a satisfaction that will put a smile on your face and keep a bundle in your pocket.

Peace.

Alfredo

The blowby test hasn't been mentioned yet. And check the front seat to see if anything has been stuffed in there. Broken/weak seat springs are very common.

Vacuum system? Central door locks.... they're a pita to troubleshoot... definitely assign a negative value to this.

Since I'm in the rust belt - rust, rust, rust...look behind the bumper rubber trims especially the corner ones. They are held by a metal bracket that probably has disintegrated and affected the body. I took off the trims on mine and removed the brackets. Fortunately, the body was only slightly affected.

Don't think that low mileage automatically means a good engine-be SURE to get maintenance records, and any rough running hot or cold means that a compression test is MANDATORY-the cost of rebuilding a motor can be twice what the car is worth!!!

A lot of excellent things pointed out here, and I wish an exhaustive list like this list existed when I was shopping.

One thing I would add is this: pull up to the seller's place in a Mercedes. Even if you have to beg to borrow someone else's. It shows that you know these cars, and you won't fall for things like, "sure it smokes, it's a diesel." Or "sure it uses oil, all diesels use oil."

One other small thing. If it's not raining, take it to car wash or just spray down with a hose to make sure all the sunroof and other drains are working properly.

Rust.

The odometers just about always break on these cars. So unless the condition or records indicate otherwise, figure at least 10k miles a year.