See Figures 1, 2, 3, 4 and 5
The exhaust system serves to conduct and silence the flow of hot gasses out of the engine. While it appears to be simple plumbing, the science of exhaust flow is quite complex. Pipe diameter, bend radius, manifold design and internal structure of components all play a part in the efficient extraction of exhaust gasses.
When performing repairs on the exhaust system, it is important to use replacement parts which are virtually identical to the originals. Failure to do so may result in impaired or restricted function and/or a host of body rattles caused by improperly mounted pipes hitting the undercarriage.
The exhaust system is generally mounted in such a way as to be insulated from the body of the car. Many rubber hangers, washers and bushings are used to reduce noise and vibration. Their placement should be accurately noted during removal so that they can be properly reinstalled. If any rubber component has lost its flexibility, it should be replaced.
Working on an exhaust system is a project of mixed emotions; being held together simply with nuts and bolts, and generally having easy access, one could lulled into thinking it a simple job. On any car more than a year old, those simple nuts and bolts have rusted solid from both heat and water. Joints have solidified and the entire system has become brittle. Chances are high that if one component has rusted through, its adjoining pieces are suspect.
Arm yourself in advance. Have a healthy supply of rust penetrant and rags on hand. In addition to the proper assortment of wrenches, you'll need good eye protection, gloves, a hammer, probably a cold chisel and possibly a small prybar. On very old systems, it is sometimes easier to simply chisel the end off the bolt and replace it than to attempt to loosen the nut. New hardware and gaskets are always recommended during any exhaust repair.
Since exhaust systems vary by engine design, fuel system and country of sale, it would be impossible to describe each component and system. Several representative diagrams have been included, showing component placement and hook up. To remove the complete system, follow the general rules below:
- Work from the front joint to the rear. If the system hangs at the rear, it can create enough force to crack or damage the exhaust manifold. In general the manifold pipe connects to the exhaust pipe near the transmission case. Loosen and disconnect the bracket holding the exhaust to the transmission case, then disconnect the joint at the manifold pipe.
- Working towards the rear of the car, disconnect the various hangers and mounts until the complete system is free of the car. Remove the system from under the car; it is easier to work on specific pipe joints with the system removed.
- Perform necessary replacements or repairs. Carefully observe the placement of all seal and gaskets when disassembling. Safe and quiet operation depends on these seals being properly installed.
- When reassembling any joint, the use of new gaskets, seals and hardware is highly recommended. Reassemble the entire system and place it under the car.
- Lift the system to the underside of the car and connect one or two of the hangers, allowing the system to swing as necessary.
- Again working from front to rear, secure the joint at the exhaust manifold and progress towards the rear of the car, installing the hangers and clamps.
- Constantly check for pipe to body interference; remember that the system is not rigidly mounted and must be free to move under the car. Minimum clearance to any body part should be 3 / 8 inch (10mm), with 1 / 2 - 3 / 4 inch (13-19mm) preferred where possible.
- It may be necessary to adjust the length of the system for proper fit. Do this by loosening the clamp at one of the pipe joints at the muffler or resonator (pre-muffler) and telescoping the pipe in or out as needed. Don't forget to retighten the clamp when the proper length is achieved.
- After the system is installed, lower the car from its elevated position. Start the engine and check for rattles and exhaust leaks. A quick check for system leaks is to protect your palm with a folded rag and place it over the end of the exhaust pipe, blocking the flow. An air tight system will develop enough pressure to push your hand away very quickly. If there's a leak, you'll be able to hear a hissing under the car.
As a rule, if any component is attached at both ends, it's easier to remove the entire system from the car and do the repair where you can see it. The rear muffler can be removed by disconnecting it at the pipe joint and then removing the hanger(s). Remember to use new gaskets and hardware when reassembling. Double check the muffler and eliminate any possible contact with the undercarriage.Catalytic Converter System
There are two different types of catalytic converters used on Volvos: the oxidation type converter and the three-way converter.
All 1975-76 Volvos manufactured for California, 1975 164 models with manual transmission and overdrive for the 49 states, 1977 49 states 240 series and all 1977 260 series, all 1978 49 states models except some 242 DL, 242 GT and 262 C models, and all 1979 49 states 240 models except the 242 GT are equipped with the oxidation type converter.
The converters are installed in these vehicles to further control emissions of carbon monoxide and hydrocarbons which have resisted the treatment of the air injection system. The converter is installed in the exhaust system ahead of the muffler. The converter uses platinum and palladium metals in a substrate or beaded form as the catalyst.
The catalyst and the oxygen supplied by the air pump then react with the exhaust gases producing harmless carbon dioxide and water vapor, as well as a minute amount of sulphur dioxide or sulfuric acid. The converter is designed to last 50,000 miles (80,515 km) as long as leaded gasoline is not used. The lead in gasoline will coat the catalytic substrate or beads, preventing the reaction process and rendering the converter ineffective.
At 15,000 mile (24,155 km) intervals, the retaining bolts for the converter must be checked for tightness. A service reminder light on the dashboard lights at 15,000 mile (24,155 km) intervals.
The 1977 California 240 series, all 1978-80 260 California series, all 1979 49 states 260 series, all 1980 and later (except diesel) models and the 1979 49 states 242 GT are equipped with three way catalytic converters.
The purpose of the three way catalytic converter is to neutralize carbon monoxide, hydrocarbons and oxides of nitrogen in the exhaust gases. The main difference between this catalytic converter and the oxidation converter is that the three way converter is able to process large amounts of oxides of nitrogen (NOx), while the oxidation catalyst cannot.
As with the oxidation catalytic converter, the use of leaded fuel or fuel additives in the engine will render the three way catalyst ineffective.