Hello everyone, I need some serious help with my 1980 Mercedes Wagon 300TD. I have multiple problems with the car and I need some help with figuring out what the problems are especially if my car doesn't sell I would love to be driving it around. Problem #1: Overheating - So when I got the car it started overheating and neither hoses going to the radiator were getting hot while the car was running so I replaced the thermostat. It was a success and I was back at it driving the car again. Recently, the car is overheating again and I believe it is the waterpump. I say it is this because the top hose is cold and the bottom hose going to the radiator is hot. It is getting no circulation of the coolant which makes me think it's the water pump. By the way, there is no leaks so I know it isn't a hose. So for the first question is, has anyone else ever have this problem and if so what was it or does anyone know what it may be? Is it the waterpump or is it something else? question #2: this question goes with the first, how do I know my head is good? I know that one way is if the head is no good the oil could be like a milky color and it isn't. It's extremely black. Now, I can't explain it perfectly but on top of the valve cover where the cap is for the oil, when the car runs for about 10 minutes, if you unscrew the cap smoke is pouring out of this hole where the oil can be seen? Is this an indication that my head is warped or bad? Defiantly a problem but I need to know what it is? There is also oil around the valve cover, not to sure if this is related to the problem but the more info I give the better! Lastly question #3; Recently I believe that my parking sensor is gone? My car will not start when in park but if I shift it into nuetral then turn the key it starts right up. So I'm asking if the parking sensor is the cause of this and if not does anyone have any idea? Well thanks guys in advance , hopefully I get some good feedback!

The starting issue may be your NSS switch. However first I would look at the grommets(bushings) in the transmission where the shifting rods go. When they wear out, the tranny does not know exactly what gear you are in and this will prevent it from starting in Park.

I have a 1981 300SD and had the same problem that you described. I thought about replacing the NSS switch but inspected the grommets first and found that one had completely disappeared (the rear one). I replaced just that one and magically the starting problem disappeared.

Good luck. Easy problem to fix if this is actually the cause.

lotsa problems, needs a good diagnosis.

overheating is more likely a clogged radiator rather than a bad water pump. water pumps leak but never stop pumping water.

the starting issue is probably the bushings mentioned.

the rest needs more info to be dealt with. good luck, chuck.

did you put thermostat in upside down? I have 368,000 miles same pump,new radiator,as they get clogged over the years.

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