What components make up the secondary air (Thermactor) system shown in this diagram?

The diagram labels an Air Diverter (AIRD) valve, an Air Bypass (AIRB) valve, check valves, a connecting hose, a crossover tube, and the air pump.

Where is the air pump located on the engine?

The left illustration shows the air pump mounted low at the front of the engine, driven off the front accessory area, with the AIR BYPASS (AIRB) valve nearby.

What is the crossover tube in this system?

The right illustration shows the crossover tube as the tube at the top of the assembly connecting the two check valves, routing secondary air across the engine.

How many check valves does the system use?

The diagram shows two check valves — the right-side exploded view labels a check valve on each side of the crossover tube, and the left view is labeled 'CHECK VALVES' (plural).

Home/ Registry/ Ford/ Bronco/ 1987-1991/ “Eddie Bauer”/ Photo supermotors.net/registry/media/988367

Ford 5.0L Secondary Air (Thermactor) System Diagram - 1990 Bronco AIRB/AIRD

Thermactor air system diagram with AIRD, AIRB valves, check valves and crossover tube

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Secondary air schematic showing the air diverter and bypass valves, check valves, crossover tube and air pump routing at the front of the engine.

AI caption July 2013 · Photo 1555 of 1799

This document is a two-part line-drawing schematic of the Thermactor secondary air injection system on a Ford V8 engine (filed by the uploader as the 5.0L system for a 1990 Ford Bronco). The left illustration shows the components installed on the engine as viewed from the front: the Air Diverter (AIRD) valve mounted high on the engine, check valves, connecting hose, the Air Bypass (AIRB) valve, and the belt-driven air pump at the lower front of the engine. The right illustration is an exploded/routing view of the same system removed from the engine, labeling the crossover tube (highlighted with a red underline), two check valves, the AIRD valve, the AIRB valve, and the air pump, with an arrow indicating the front of the engine for orientation. A reader can learn the identity, relative location, and hose/tube routing order of each secondary air component: air flows from the air pump through the AIRB (bypass) valve, then to the AIRD (diverter) valve, through the check valves, and into the crossover tube feeding the exhaust. The document contains no text stating year, model, engine displacement, part numbers, or torque specifications — identification of components is by callout labels only.

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Frequently asked questions

What components make up the secondary air (Thermactor) system shown in this diagram?: The diagram labels an Air Diverter (AIRD) valve, an Air Bypass (AIRB) valve, check valves, a connecting hose, a crossover tube, and the air pump.
Where is the air pump located on the engine?: The left illustration shows the air pump mounted low at the front of the engine, driven off the front accessory area, with the AIR BYPASS (AIRB) valve nearby.
What is the crossover tube in this system?: The right illustration shows the crossover tube as the tube at the top of the assembly connecting the two check valves, routing secondary air across the engine.
How many check valves does the system use?: The diagram shows two check valves — the right-side exploded view labels a check valve on each side of the crossover tube, and the left view is labeled 'CHECK VALVES' (plural).
What is the flow order of the secondary air components?: Per the exploded view, air goes from the air pump to the AIRB (bypass) valve, then to the AIRD (diverter) valve, through the check valves, and into the crossover tube.