Renault vel satisf

Hello I have a renault vel satisfies and the case is that when you whet more than 30 km without stop+o- the temperature is triggered, instead if you are streets the temperature is maintained in its normal position. The cluster joint is already checked by putting air, thermostat, water pump, refrigeration circuit. The question is that the hoses get dirty when it warms up and the strange pressure on the circuit. Thank you all and greetings.

Haber,

the Board is well
the thermostat also
the water pump also
the refrigeration circuit also

.........

and the most difficult thing yet ... when it is stalling does not heat up, it heats up when you have a constant rhythm on the highway.

Do you leave me Atonito.

Won't it be that the temperature clock is cheating you?

If you discover the cause, please comment here.