1985 International S-Series

The International S-Series “Schoolmaster” was a Type C bus chassis developed by International Harvester, later becoming Navistar. It was designed to move schoolchildren. A successor to the Loadstar bus chassis, it was introduced in 1979 and used for school buses and commercial buses until the late 1990s. In 1989, it was replaced by the International 3800, with both chassis being made available in that year. The Schoolmaster was the last bus chassis type produced by International Harvester. Here we will focus on the 1985 International S-Series chassis.

Developed by International Harvester between 1979 and 2001, the 1985 International S series bus chassis type is a cowled bus chassis with a steel frame. Designed mainly for school bus applications, the chassis was also used in commercial-use buses and cutaway-cab buses in certain instances. The cowled chassis also served as the foundation for creating stripped chassis with front-engine and rear-engine configurations for use in bus transportation applications.

The S-series bus chassis was developed to replace the International Loadstar and was available in two different configurations. In 1989, the International 3800 model line was completely redesigned to correspond with the progression of the International S series, which was introduced the previous year. It was succeeded by the International 3300 (a cowled-chassis derivative of the International 4300/DuraStar) when the International 3800 was retired in 2004. Founded in 1959, the S-series bus chassis was the longest-running design line ever produced by International Harvester. It was also the company’s final Navistar product line to be made.

Performance and Fuel Economy

When it was first introduced, the 1985 International S-Series Schoolmaster was offered a choice of four gasoline engines and three diesel engines. The S1723 was powered only by gasoline engines, with the International 345 V8 serving as the standard engine and three additional gasoline V8s as options (the 392 and the MV404, and the MV446). The S1823 was only offered with V8s from the MV series (which ended production after 1981). In addition to a standard 9.0L V8 engine, the S1853 could be equipped with DT466 and Caterpillar 3208 diesel engines, among other choices.

The suspension weight capacities of the two model ranges and the engine options were the primary differences between them. The Schoolmasters’ model numbers ended in three digits by international conventional model nomenclature; gasoline-engine specimens were issued model numbers beginning with “23,” while diesel-engine examples were awarded model numbers beginning with “53.”

1985 International S-Series Chassis Factory Service Manual

The service manuals for 1985 International S-Series chassis vehicles are comprehensive, covering every vehicle service and repair procedure. Every 1985 International S-Series service manual should accompany a repair. The service manuals go into great depth on the following topics:

  • Frame
  • Lubrication
  • Steering
  • Exhaust
  • Electrical
  • Springs
  • Engine
  • Transmission
  • Rear Axle
  • Brakes
  • Fuel Tanks

S-Series repair manuals are designed for technicians and dealerships that frequently maintain and repair the brand’s vehicles. Using these service manuals, the owner may ensure that any automotive maintenance or repairs are done correctly and precisely on every occasion. Owners and mechanics may also find it necessary to consult the International Truck Wiring Diagram Schematic to address any electrical issues.

Design, Comfort, and Quality

Throughout its production life, the Schoolmaster had only minor modifications. Numerous improvements were made to reflect its shift from International Harvester to Navistar. In 1987, a new International symbol was installed on the grille and steering wheel, replacing the previous one. Additionally, all gasoline engines were eliminated from the S-Series bus chassis powertrain choices, marking the industry’s first time this has happened. In 1989, Navistar made major modifications to the S-Series trucks, renamed the 4000-Series. It was necessary to modify the bus chassis from the firewall forward, and the whole dashboard had to be replaced. The 3800 bus chassis was the name given to the new-generation bus chassis, which was produced in 2004. Thus, the 3800 was produced as the last S-Series variant before being phased out of production.

The Schoolmaster was built using powertrains and components derived from the S-Series medium-duty truck line. There were two models available: the S-1700 and the S-1800, both heavier-duty. As an additional service, International gave a stripped chassis to school bus manufacturers who were building Type D (transit type) school buses. The 1853-FC (FC = Forward Control) was powered only by diesel engines. The 1853FC was replaced in 1989 by the 3900, which was in service with Navistar until its deactivation in 2010.


Engine type: V8, Gasoline, Diesel

Vehicle type: School bus

1985 International S-Series

1985 International S-Series — Owner’s Manual

The owner’s manual for a 1985 International S-Series includes all of the key facts concerning the vehicle’s future operation and maintenance.

  • Safety and Security
  • Operation of each component
  • Driving
  • Interior Features
  • Maintenance and care
  • Vehicle specifications

This owner’s manual, developed just for vehicle lovers, will explain when and how to utilize their vehicle’s various features and functions in detail.