Ken,

I have two W140's my S320 is my favorite car...

The S320's are known for oil leak from the head gasket on the rear cylinder. Some may look barely wet(like mine), some may drip badly, and some blow the head gasket.

Also, the S320 was the last year of the all hydraulic transmission, and reverse gear is the biggest issue with the 722.5. One of the o-rings responsible for the reverse gear gets brittle and hard; No longer seals well. The o-ring gets worse as the transmission heats up, yet prior to loosing reverse. Reverse gear makes this clicking sound like you are on a roller coaster up hill. My S320 started to make the clicking at 125k, and reverse failed at 135k. I just finished rebuilding the transmission my self. The reverse should be quite. 722.5 like the 722.4 and 722.3 need additional cooling(a separate transmission cooler). While I've been barely driving my S320 after the transmission rebuild one of the transmission rubber cooler lines was brittle hard cracked, and sprung a leak. These cooler lines are behind the bottom front engine cover.

When you get your S320, do not go joy riding. Change out the heater tee on the fire wall. Replace the tee with a actual fresh new part from the dealer-no third party-ebay deals-used ones. The tee will break and spew coolant everywhere, and you have 30 to 60 seconds to respond before the engine is destroyed. The tee's should be changed at 70k to 80k. Mine broke at 125k, but I was lucky...

On the level of heater, test to make sure the heater and AC works. The Fan speed goes up and down. The heater is usually a stuck or damaged DUO valve. The Fan speed is a active voltage fan regulator that is known to fail.

This leads to the next question, I'd probably walk away from a car that the prior owner has replaced the entire head as the car has over heated on them. These cars are not the same after that happens.

The early engine wiring issue was solved after 1996, but the S320 still has a wiring issue(not in the engine). The problem is in the mirrors. Fold the mirrors(they fold electrically). If the mirrors stop(because the fuse popped), it is the wiring is bare, and shorting with other wires. You can usually see the bare wires while the mirrors are folded.

Obviously, no lights on instrument. Look at the oil on each of the dip sticks. Inspect the "radiator cap" the color of the coolant should not be GREEN or ORANGE...If it is green or orange, I would run not walk away from the car!



If the key is hard to turn, locks up some times. The tumbler/key assembly is about to fail, and when it fails it is a very VERY Expensive fix from the dealer(only!!) in the Thousands....

The rest of the stuff is peanuts.. Door lock does not work, windows do not go up, doors not suck in, trunk does not close, antenna does not go up or down, volume on radio jumps, sound sounds with static(its the amp), etc.. these are easy.

I hope you will DIY on the S320 because you will pay through the nose for service, as the W140 requires higher interval of service(it just has more parts to fail). Get a 2000 to 2002 E series if someone is going to service the vehicle.

If you can get PPI inspection, that will aid in your selection.

Best of luck,

Martin