Ram B1500, B2500, B3500, 1999-2003

Exhaust System


Catalytic Converter

Description & Operation

The catalytic converter, mounted in the exhaust system, is a muffler-shaped device containing a ceramic honeycomb shaped material coated with alumina and impregnated with catalytically active precious metals such as platinum, palladium and rhodium.

The catalyst's job is to reduce air pollutants by oxidizing hydrocarbons (HC) and carbon monoxide (CO). Catalysts containing palladium and rhodium also oxidize nitrous oxides (NOx).

On some trucks, the catalyst is also fed by the secondary air system, via a small supply tube in the side of the catalyst.

No maintenance is possible on the converter, other than keeping the heat shield clear of flammable debris, such as leaves and twigs.

Other than external damage, the only significant damage possible to a converter is through the use of leaded gasoline, or by way of a too rich fuel/air mixture. Both of these problems will ruin the converter through contamination of the catalyst and will eventually plug the converter causing loss of power and engine performance.

When this occurs, the catalyst must be replaced. For catalyst replacement, see the Exhaust System procedures under "ENGINE AND ENGINE OVERHAUL."


Safety glasses should be worn at all times when working on or near the exhaust system. Older exhaust systems will almost always be covered with loose rust particles which will become airborne when disturbed. These particles are more than a nuisance-they could injure your eyes.

When working on the exhaust system always keep the following in mind:

Check the complete exhaust system for open seams, holes loose connections, or other deterioration which could permit exhaust fumes to seep into the passenger compartment.
The exhaust system may be supported by free-hanging rubber mounts which permit some movement of the exhaust system, but block the transfer of noise and vibration into the passenger compartment. Do NOT replace rubber mounts with solid ones.
Before removing any component of the exhaust system, ALWAYS squirt a penetrating lubricant or rust dissolving agent onto the fasteners for ease of removal. A lot of knuckle skin will be saved by following this rule.

Because some penetrating fluids are flammable, NEVER use them on a hot exhaust system or near an open flame.

Annoying rattles and noise vibrations in the exhaust system are usually caused by misalignment of the parts. When aligning the system, leave mounting hardware loose until all parts are properly aligned, then tighten, working from front to rear.
When installing exhaust system parts, make sure there is enough clearance between the hot exhaust system components and other pipes and hoses that would be adversely affected by excessive heat. Also make sure there is adequate clearance from the floor pan to avoid possible overheating of the floor.


For a number of reasons, exhaust system work can be among the most dangerous type of work you can do on your truck. Always observe the following precautions:

Support the truck extra securely. Not only will you often be working directly under it, but you'll frequently be using a lot of force, say, heavy hammer blows, to dislodge rusted parts. This can cause a truck that's improperly supported to shift and possibly fall.
Wear goggles. Exhaust system parts are always rusty. Metal chips can be dislodged, even when you're only turning rusted bolts. Attempting to pry pipes apart with a chisel makes the chips fly even more frequently.
If you're using a cutting torch, keep it a great distance from either the fuel tank or lines. Stop what you're doing and feel the temperature of the fuel bearing pipes on the tank frequently. Even slight heat can expand and/or vaporize fuel, resulting in accumulated vapor, or even a liquid leak, near your torch.
Watch where your hammer blows fall and make sure you hit squarely. You could easily tap a brake or fuel line when you hit an exhaust system part with a glancing blow. Inspect all lines and hoses in the area where you've been working.

Be very careful when working on or near the catalytic converter. External temperatures can reach 1,500ºF (816ºC) and more, capable of causing severe burns on contact. Headers also get extremely hot in use and require adequate cool-down time. Removal or installation should be performed only on a cold exhaust system.

Removal & Installation

A number of special exhaust system tools can be rented from auto supply houses or local stores that rent special equipment. A common one is a tail pipe expander, designed to enable you to join pipes of identical diameter

System components may be welded or clamped together. The system consists of a head pipe, catalytic converter, intermediate pipe, muffler and tail pipe, in that order from the engine to the back of the truck. Some extensions may be fitted between major components to compensate for variations in wheelbase, transmissions, or other chassis obstructions.

The head pipe is bolted to the exhaust manifold, on one end, and the catalytic converter on the other. Various hangers suspend the system from the floor pan. When assembling exhaust system parts, the relative clearances around all system parts are extremely critical. Observe all clearances during assembly.

In the event that the system is welded, the various parts will have to be cut apart for removal. In these cases, the cut parts may not be reused. To cut the parts, a hacksaw is the best choice. An oxy-acetylene cutting torch may be faster, but the sparks are DANGEROUS near the fuel tank, and, at the very least, accidents could happen, resulting in damage to other under-truck parts, not to mention yourself!

The following replacement steps relate to clamped parts:

  1. Raise and support the truck on jackstands. It's much easier on you if you can get the truck up on four jackstands. Some pipes need lots of clearance for removal and installation
  3. Remove the nuts from the U-bolts. Don't be surprised if the U-bolts break while removing the nuts. Age and rust account for this. Besides, you shouldn't reuse old U-bolts. When unbolting the header pipe from the exhaust manifold, make sure that the bolts are free before trying to remove them. If you snap a stud in the exhaust manifold, the stud will have to be removed with a bolt extractor, which often necessitates the removal of the manifold itself.
  5. After the clamps are removed from the joints, first twist the parts at the joints to break loose rust and scale, then pull the components apart with a twisting motion. If the parts twist freely but won't pull apart, check the joint. The clamp may have been installed so tightly that it has caused a slight crushing of the joint. In this event, the best thing to do is secure a chisel designed for the purpose and, using the chisel and a hammer, peel back the female pipe end until the parts are freed.
  7. Once the parts are freed, check the condition of the pipes that you had intended keeping. If their condition is at all in doubt, replace them too. You went to a lot of work to get one or more components out. You don't want to have to go through that again in the near future. If you are retaining a pipe, check the pipe end. If a clamp crushed it, it can be restored to its original diameter using a pipe expander.

Check the condition of the exhaust system hangers. If ANY deterioration is noted, replace them

Use only parts designed for your truck. Don't use "universal" parts or flex pipes. "Universal" parts rarely fit like originals and flex pipes don't last very long.

  1. When installing the new parts, coat the pipe ends with high temperature lubricant. It makes fitting the parts much easier. It's also a good idea to assemble all the parts in position before clamping them. This will ensure a good fit, detect any problems and allow you to check all clearances between the parts and surrounding frame and floor members.
  3. When you are satisfied with all fits and clearances, install the clamps. The header pipe-to-manifold nuts should be torqued to 20 ft. lbs. (27 Nm). If the studs were rusty, wire-brush them clean, and spray them with a lubricant. This will ensure a proper torque reading. Position the clamps on the slip points. The slits in the female pipe ends should be under the U-bolt, not under the clamp. Tighten the U-bolt nuts securely, without crushing the pipe. The pipe fit should be tight, so that you can't swivel the pipe by hand. Don't forget: always use new clamps.
  5. When the system is tight, recheck all clearances. Start the engine and check the joints for leaks. A leak can be felt by hand.


  1. If any leaks are detected, tighten the clamp until the leak stops. If the pipe starts to deform before the leak stops, reposition the clamp and tighten it. If that still doesn't stop the leak, it may be that you don't have enough overlap on the pipe fit. Shut off the engine and try pushing the pipe together further. Be careful; the pipe gets hot quickly.
  3. When everything is tight and secure, lower the truck and take it for a road test. Make sure there are no unusual sounds or vibration. Most new pipes are coated with a preservative, so the system will be pretty smelly for a day or two while the coating burns off.

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Fig. Cracks in the muffler are a guaranteed leak

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Fig. Check the muffler for rotted spot welds and seams

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Fig. Clean around the edges of the flange gasket with a sharp pick to help with the removal of the sealing ring

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Fig. Make sure the exhaust components are not contacting the body or suspension

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Fig. Check for overstretched or torn exhaust hangers

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Fig. Example of a badly deteriorated exhaust pipe

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Fig. Inspect flanges for gaskets that have deteriorated and need replacement

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Fig. Some systems, like this one, use large O-rings (doughnuts) in between the flanges

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Fig. Nuts and bolts will be extremely difficult to remove when deteriorated with rust

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Fig. Example of a flange type exhaust system joint

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Fig. Example of a common slip joint type system