Abstract: A service-interval display for motor vehicles, which generates a signal when a limiting parameter value is reached. Total fuel consumption serves as the basic parameter instead of the distance travelled, previously employed. Other parameters may serve to modify the generation of the signal to cause an earlier or later warning to be displayed.

Abstract: A service interval display unit for a motor vehicle for alerting the operator of required maintenance wherein actual distance traveled by the vehicle is monitored, and as a factor in determining the service interval, operating parameters such as engine speed, coolant temperature, oil temperature, and/or fuel consumption rate are taken into consideration on a weighted basis to assert earlier a service signal in the display unit when the engine experiences increased periods of higher loads. The display unit includes a series of indicators which are successively extinguished upon attainment of subintervals during the maintenance cycle and warning lights which are energized after attainment of the service interval. Additional warning lights also are provided for emphasizing the expiration of the service interval when the vehicle is operated successive fixed distance intervals beyond the regular service interval.

Abstract: A service-interval display for motor vehicles, delivers a signal after a fixed distance has been traversed, the fixed distance (D) is divided into several fixed service distance intervals (i.sub.d) of equal length, and a plurality of individual signal elements, each of which changes its switch status at the end of successive intervals, is assigned to each of these intervals. The number of signal elements activated is an indication of the incremental approach to arrival at and travel beyond the fixed distance (D).

Abstract: In a cooling circuit for internal combustion engines which includes a cooling jacket of the engine, a coolant pump, a radiator, a mixing thermostat, and an expansion tank, an excess-pressure valve is connected in the area between the cooling jacket and the radiator and a vacuum valve is connected in the area between the radiator valve of the mixing thermostat and the suction side of the coolant pump; both valves are connected with the coolant reservoir in the expansion tank which in communication with the atmosphere, is without excess pressure; high excess pressure values as well as low vacuum values in the cooling circuit are precluded thereby; a vent valve provides for an especially effective venting of the cooling circuit into the expansion tank in cooperation with the sucking back of coolant into the cooling circuit by means of the vacuum valve.