Prices for 300E's range from $6,000 to about $14,000 depending upon age and condition. When shopping for a 300E - or any used Mercedes-Benz for that matter - the most important things you can do are:

• Look for one that has obviously been well cared for.
• Look for one that has a known, documented service and maintenance history.
• Have a pre-purchase inspection performed by a shop that specializes in Mercedes-Benz.

A well-cared for 300E will last forever. Parts do wear out and must be replaced, however. In addition, there are a few well-known problem areas. A documented service history will enable you to determine how much of this necessary maintenance has already been done. A good pre-purchase inspection will also reveal other problem areas. My local independant Mercedes-Benz shop charges $65 for such an inspection. Most shops charge up to about $200. It may be the most important money you spend on your Mercedes-Benz.

Most 300E's today have 120,000 to 200,000 miles on them. Things wear out. Here are some of the things to look for:

Oil Leak at Top Timing Chain Cover

The original gasket sealing the top timing chain cover (some call it the front valve cover) will eventually leak. This problem is not serious, but oil dripping on your nice clean garage floor is a nuisance. Look for oil on the engine block near the front on the right-hand side between the block and the alternator.

Fortunately, the leak seldom gets worse and can be dealt with by a drip-pan under the car. One shop sells a W124 Engine Diaper Kit that attaches inside the lower engine compartment cover and absorbs the leaking oil. A permanent fix - replacing the gasket - cost about $500 for my M104 engine. The repair cost on the M103 engine would be lower.

Head Gasket

This is not as bad as it sounds. There is an area near the right rear of the engine-block mating area where an oil channel and a water channel run close together, and also the oil channel is very near the outside edge. Over time, the original head gasket tends to seep a little in this area. Sometimes the gasket material between the oil channel and water channel gives way. Look for a slight oil film in the wather reservoir. Look oil leaking on the right side of the block near the back.

If the oil in the water resevoir is minimal, it can be sucked out with a turkey baster. (Come on guys, don't use your wife's turkey baster. Buy your own.) Just as with the top timing chain cover gasket, this is a problem you could live with indefinitely. Replacing the head gasket on my 300E cost about $1100.

If you do choose to have this done, try to combine it with some other significant maintenance work such as the aforementioned top timing chain cover or replacement of the timing chain. It is also a great time to really scrutinize all of the hoses and such that are not normally so well exposed.

Timing Chain

Most manufacturers use a rubber belt between the crankshaft and camshaft. Mercedes-Benz is one of the few who still use a metal timing chain instead. Over time, the chain will stretch. A tensioner takes up the slack. The service life of the timing chain in a 300E is typically 250,000 to 300,000 miles. Sometimes however, (if the oil has not been changed frequently, for example) the service life can be much less. At 120,000 - 150,000 miles it is advisable to have a reputable shop check the timing chain. For the M104 engine, it is my opinion that when you check the timing chain wear, the incremental cost to replace the chain is small enough that you should just go ahead and replace it anyway.

The cost of the repair after the chain breaks is about ten times the cost of replacing the chain. If you are buying a 300E with 100K-150K miles, this is where the documented service history is desirable. If there is no record that the timing chain has been checked or replaced, assume that you need to do it.

Engine Wiring Harness

Mercedes-Benz used a type of insulation which was supposed to be biodegradable. The result is that given sufficient time and heat, the insulation gets hard and brittle. Everything works fine until you need to move a piece of the harness out of the way to fix something. then the insulation on the individual wires cracks, shorting wires together and all sorts of strange symptoms occur. It's enough to drive a shadetree mechanic crazy unless he is aware of it. The Engine Wiring Harness is very expensive. Your best bet on a replacement is probably Randy Steele.

Radiator

The hose fittings on the 300E radiator are plastic. Sometimes the neck of the hose fitting for the top radiator hose will crack. Look for coolant residue around the neck. Interestingly, a well-known shop reports that he has never seen this problem on a 300E that used the MB coolant exclusively.

Warning Lights

Here is a tip: When inspecting a 300E that you are considering buying, one of the first things you should do is to put the key into the ignition, turn it to the first detent, and inspect all the warning lights at the bottom of the instrument cluster. They should all come on. I repeat: all the warning lights should illuminate for a second or two after turing the key to the first detent. The important ones are the ABS and SRS lights (Some years of 300E did not have one or the other so check the owner's manual.) If one of these expensive systems has failed, an unscrupulous seller may remove the bulb for the failing system, thus hiding the failure from the buyer.

Air Conditioning

When inspecting a 300E that you are considering buying, during the test drive turn the air-conditioning on. Referring to the illustration,select button 'b', rotate the temperature control 'a' to its coldest, and set the fan to 'Auto' (button 'c'). Air should be coming out of all of the vents on the dash facing you. Air should not be coming from the defroster vents at the base of the windshield (unless you have just started the engine and it has not yet operated at anything above idle). The flow of air is controled by several vacuum-operated servos (pods) within the dash. Over time, the diaphrams in the pods crack and no longer hold vacuum. Almost every 300E that has not had the pods replaced will leak a little air through the defroster vents and that should not be cause for alarm. A lot of air however is a no-no. Replacing these pods involves removing the entire dash, about 1 day's labor at best, and about $500 for the parts.

Watch out for vehicles that 'just need a little freon'.

Conclusion

The Mercedes-Benz 300E is designed to be a very durable, servicable car. If you are looking at a 300E with 100,000 miles on it but the stuff listed above has been done, then you certainly can expect another 100,000 miles out of the car.