Need help with a transmission and overheating problems

[Bonus_HUN]

Good day everyone!

Sorry in advance for my terrible english, I'm hungarian.

I have a 2001, 0.6 Smart fortwo 450.341 automatic transmission model, and lately I noticed, that when I start driving, the car sort of "jumps" forward, and also does that after every single shift. Not sure how else I could describe it. The car doesn't start going gently, but it does a small jump forward.

The other problem I'm having is, that in the beginning(according to the temperature gauge) only half a minute after I start driving the water temperature goes up to 100C (and even 120C) and after a while it just goes back down to normal 60C.
Now it even does that mid driving, so once I was driving for 20 minutes, the temperature was okay (60C) and the heating in the cabin was working. Then suddenly the temp started going up again and the heater was blowing in cold air, until a few minutes later the water temp went back to normal again and I had heating again. For some reason the water level is dropping, because a few days after filling it up, there was only 1/4 left, however I found no leakage spots on the concrete under the car, so I'm not sure if it's leaking or evaporating, or why the car drinks all the water.

Has anyone had these problems before, and does anyone know a way to fix these?
Any advice would be greatly appreciated

[heinkeljb]

It sounds like you have the two following problems:-

1: The transmission issue could be down the wires going to the Clutch. There is a well know problem with the wires getting damaged where they come through the plastic housing of the Intercooler scoop. Find the Clutch actuator and follow the wires to where they go into the plastic. That is where there is possibly a break in some of the strands of the wires.

It could also be down to the Clutch pack itself, this has some metal straps inside which can break. This would mean taking the clutch out to check.

2: The overheating / sudden change in temperature is down to a leak and as a consequence there is a air lock in the system. You need to trace where the leak is. If you can not see it showing as water pouring out on the outside, it must be going inside the engine. There are two place it can go, First is into the oil - take the oil filler cap off and check to see if you have a white mixture covering the chain / inside of the cap. Second take out the spark plugs and see if they are all covered in rubbish -.

If either of those two things are true, then you will have to take teh cylinder head off and replace the head gasket.

John