Catalytic Converter Cadillac Brougham I

The catalytic converter is located in the exhaust system prior to the muffler. The catalytic converter is an emission control device added to the gasoline exhaust system to reduce hydrocarbon and carbon monoxide pollutants from the exhaust gas stream.

There are 3 types of catalytic converters: Conventional Oxidation Converters (COC), 3-Way Catalyst (TWC) and dual bed catalytic converters which are a combination of both the above mentioned. All catalytic converters are of 2 designs: non-serviceable, honeycomb-type block, or a small canister containing catalytic beads.

Both converters contain a base material of alumina impregnated with platinum/palladium, while 3-way catalysts in addition to this also contain a material coated with platinum/rhodium. Both converters reduce hydrocarbons and carbon monoxide, while the TWC also reduces oxides of nitrogen.

Note. Use only unleaded fuel on vehicles equipped with a catalytic converter. If leaded fuel is used, coating and destruction of the catalytic surfaces will result and replacement is required.

On some models, a TWC is used in conjunction with a COC both contained in the same canister. Working in conjunction with this, there often is an air injection pipe. This pipe injects air between these 2 beds to help further oxidize the exhaust gases. This is called a dual-bed converter. (Scheme 19)

On all other dual bed converter models, the first converter (3-way) in the exhaust system reduces hydrocarbons (HC) and carbon monoxide (CO), but mainly deals with oxides of nitrogen (NOx). In the second converter (oxidation type), with extra help from the air pump, reduction of hydrocarbons (HC) and carbon monoxide (CO) takes place.

Scheme 19

HEAT SHIELDS

The combustion reaction, which is aided by the converter, releases additional heat into the exhaust system. Temperatures in catalytic converters can reach 1600°F (870°C) under normal conditions. DO NOT remove special heat shields used to protect the underbody and under-vehicle components from extreme heat.

MAINTENANCE

There is no scheduled maintenance of a catalytic converter, it is designed to last the lifetime of the vehicle. If it does not perform correctly, replace it.

RESTRICTED EXHAUST SYSTEM

A restricted or blocked exhaust system usually results in loss or lack of power or popping through carburetor. Ensure that the condition is not caused by timing or ignition problems before testing for restricted exhaust system. See appropriate CHART B-1 in COMPUTERIZED ENGINE CONTROLS section.

To test for restricted exhaust system, you will need a Bourroughs Exhaust Backpressure Tester (BT 8515 or BT 8603). Or if testing at Air Injection Reactor (A.I.R.) pipe, connect hose and nipple from Propane Enrichment Device (J26911) to a fuel pump pressure gauge. (Scheme 20)

Scheme 20

Check At A.I.R. Pipe

Remove hose and check valve at exhaust manifold A.I.R. pipe. Assemble hose and nipple to fuel pump pressure gauge. Insert nipple into exhaust manifold A.I.R. pipe. Go to step 1).

Check At O2 Sensor

Remove O2 sensor and install Bourroughs Exhaust Backpressure Tester (BT 8515 or BT 8603). Go to step 1).

1. With engine idling at normal operating temperature, observe gauge reading. Compare with specification table (If applicable). The reading should not exceed specification. Increase engine speed to RPM specification and observe gauge. Compare with specification.
2. If one or more readings exceeds psi (kg/cm 2 ) specification, restricted exhaust is indicated. Inspect entire system for common causes such as collapsed pipe, heat damage or internal muffler failure. If no other cause is found the catalytic converter is suspect and should be replaced.

SPECIFICATIONS

EXHAUST SYSTEM BACKPRESSURE SPECIFICATIONS