The Renault Express gets too hot

First of all say that I am a total useless mechanics, so I am writing any burda, forgive.
I tell you my case, I have an Express 1.9Diesel, and for a few days, it heats up too much, it does not reach the red area of ​​the temperature clock, but sometimes it is very little missing, when that happens, the radiator jumps and lowers the temperature little by little, sometimes sometimes, when I am going to open the water storage, even if it is hot, the water is boiling and it comes out quite a lot of the deposit, the level is in its place, the level is in its place, the level is in its place, the level is in its place, the level is in its place.
The temperature sensor has changed it 1mes, although the cable that goes to that sensor seems that it does not work, because I disconnect it and touch some metal part of the engine with it and does not give xispa, nor being torn the van or just with the contact.
I have to say that the van was stopped for almost two years, andq the refrigeration circuit is quite dirty, although 1 week ago I clean it with liquid from that D eliminate radiators.
The water does not bubble me and the oil has normal color and does not lower level, so I want to think that it is nothing of butts.
When I start it for the first time, the morning releases a lot of white smoke, but then no longer (I hope it is not the cylinder head).
I have been reading online that it can be the radiator plug or that of the water storage, or the thermostat. Some tell me where the thermostat and the radiator plug is?, If anyone tells me that it can be I would appreciate it, I have taken it to the mechanic and tell me that in principle it discards button and that I have a monthly cleaning to the circuit, and forgive the sheet hehe

I do not know about Diesel Renault vehicles, but normally the renault do not use water but coolant, for those who use water you must take out the radiator hose that is the top, pear you take it from the side of the engine, you will find a lid with a spring and you can see that it oxidizes that lid is called temperature thermostat, this is so that it does not synthes It is what is happening to you, you can simply remove and mount the hose again, but until the vehicle is not hot you will have failure and in cold climates it is not recommended, on the other hand in diesel systems either. As for your problem with the temperature sensor, many of these say that if you touch the sensor part with your finger or hand before mounting it, it throws erroneous readings. Check that the code that your old sensor has a lateral written, is the same as the new one.

Good night the Renault engines are very dirty and oxidize the refrigerant fluid so do not scare yourself, if the electrventillator probably jumps the thermostat is good I personally clean the radiator on the outside with a pressure hose under pressure me. Three thermocontact temperatures, it is a diesel engine and it is very important that it works at an adequate temperature, another thing I have read something that the engine worked with water, the engine fluid must be antifreeze the properties of this not only avoid the freezing point but also delay the boiling point of the liquid 120 graphs approximately, greetings and luck you will tell us that it is going with it.

Greetings
to rule out butt or thermostat There are simple tests, x If you are interested

with the cold engine when you are going to turn it on,
1, lift the cape
2, take out the radiator lid
3, ask someone to turn on your car while you look at your views carefully the radiator
4, you look if it comes out like a water or refrigerant volcano, as a choro volcan up then you have problems.

Hot the car asta that reaches the temperature,
1, verify that the radiator lid
2 is set, you look on the board that the pen is in the medium
3, you will touch with your hands be very careful 2 thick hoses that leave the radiator,
4, this hoses are a top and one below, if these are +o- at the same temperature, the earthly is good
5, if the hose is hot Thermostat, it is dagged.

If you change the thermostat, change regrigerant and lid of the eye radiator with this it has to be the same if possible original, do not put everything of refrigerant, look the specifications, if you put a lot this is more viscous than the water, it is to say, that it moves more slow than the water, 3/4 of refrigerant and 1/4 of water

also also Nothing, this dana your radiator, a good refrigerant is for $ 50 at $ 80 American dollars the galon

Thank you all for the aid, but in the end they were the sleeves, which were starting to fail until you broke two and I changed them, the one that goes from the upper part of the radiator to the engine, I also changed it, because I had peqeñas cracks and seen what I saw preferred to change it.
At the moment I am doing well, as soon as the temperature reaches 85-90 degrees, the fan jumps and now it never approaches the red zone.
I am using water at the moment, because the mechanic told me to use water for about two months for the circuit to be cleaned a little and that I would not miss any more water, but that after those two months and if everything goes like now, that it makes antifreeze.

Another doubt, there some product to protect the engine, reduce consumption and others .... I have heard of the metal-lube and the Nextron, but I do not know if it will be good for my van, although with almost 20 years and 226000km, any help for a small thing that is welcome.