Revving but RPMs zero, oil press zero!

Don't know how to start this there are so many symptoms.

In the morning the engine fires up with no problems what so ever. But if i turn it off let's say after 30 miles, than after 10 - 15 minutes it sure starts but whole #### hits the fan!
So here we go what i am talking about.
Situation 1 -
First I give contact. Temperature coolant gauge goes stupid - over the max off the scale!
Situation 2 -
Than I start the engine and immediately it revs by itself till 1500rpm and stays there but RPM gauge stays on zero and also oil pressure stays on zero...


That must be some kind of a record!
Than what do i do? After 10 min it starts like normal and drives normal even for hours, no lack of power, nothing to worry...

Mechanics found out on situation 1 some computer doesn't have voltage. They also found out temp sensors are OK, connectors and relays are OK etc.
They said it's computers fault because there can't be so many symptoms at once...

As a driver for a year with this bus i noticed for years they fill too much oil - 2,5 gallons too much as in the manual. I may be wrong this is the cause. For sure it ran great even with this much oil. For a matter of fact i had to fill a bottle every few weeks otherwise it would rev on it's own for 10 seconds or so. Of course oil stick was always showing too much oil...
I noticed also oil level relay is missing, if that helps.

Anyway something goes bizarrely wrong when the vehicle is sitting there with the engine turned off and hot. My guess is when the engine is turned off coolant temp rises of course because whole thing is hot and "visco" (as we call it) is not working. Than it will start normal only when it cools down.
But that's a guess...

 

Too much oil is bothering me too.
This week i did a bit of investigation on same model engines in my company. They are all filled with 2.5 gallon of oil to much.
I noticed also the engine is vibrating - juddering in cycles. Every few seconds you can feel slight judder. A mechanik said it could be an injector...
Chief mechanik said "well than just start the engine 5 min later when it gets better... loool

 

and yes it's confirmed!
It was engine computer fault as our mechanics call it. Interesting before the replacement a serviceman from Mercedes came with big case of computers and stuff and he still couldn't find the problem!

Anyway the part is already changed to brand new and the motor is running way better - smooth, silent, no warning lights, no symptoms like i described in first post. And there were really many of them.
There was no so called "Christmas tree" - when there are many warning lights showing - instead it was like pulling your hair out!
Now if i "roll back" it was like driving god #### LOCOmotive and notice the LOCO....