Volkswagen Air-Cooled 1970-1981 Repair Guide

Exhaust Gas Recirculation System

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In order to control exhaust emissions of oxides of nitrogen (NO;zx), an exhaust gas recirculation (EGR) system is employed on 1972 Type 1 and Type 3 models equipped with automatic transaxles and sold in California, on 1973 Type 1 and Type 3 models equipped with automatic transaxles sold nationwide, on all 1973 and later Type 2 models, on all 1974 Type 4 models equipped with automatic transaxles, and on all 1974 and later Type 1 models. The system lowers peak flame temperature during combustion by introducing a small (about 10%) percentage of relatively inert exhaust gas into the intake charge. Since the exhaust gas contains little or no oxygen, it cannot react with, nor influence the air/fuel mixture. However, the exhaust gas does (by volume) take up space in the combustion chambers (space that would otherwise be occupied by a heat-producing, explosive air/fuel mixture), and does serve to lower peak combustion chamber temperature. The amount of exhaust gas directed to the combustion chambers is infinitely variable by means of a vacuum operated EGR valve. For system specifics, see the vehicle type breakdown under "General Description."

GENERAL DESCRIPTION TYPE 1



See Figures 1 and 2

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Fig. Fig. 1: Exhaust Gas Recirculation (EGR) system-1972 Type 1 California models equipped with the automatic stick shift transaxle



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Fig. Fig. 2: Exhaust Gas Recirculation (EGR) system-1973-74 Type 1 models

For 1972, EGR is used only on automatic stick shift models sold in California. Exhaust gas is drawn from the left-hand rear exhaust flange and then cooled in a cooling coil. From here, the gas is filtered in a cyclone filter and finally channelled to the intake manifold, via the EGR valve. The valve permits exhaust gas recirculation during part throttle applications, but not during idling or wide open throttle.

All 1973 models (nationwide) equipped with the automatic stick shift transaxle use an EGR system. As in 1972, the gas is drawn from the left, rear exhaust flange. However, instead of the cooling coil and cyclone filter, a replaceable element type filter is used. The remainder of the system remains unchanged from 1972.

All 1974 Type 1 cars, regardless of equipment, are equipped with the EGR system. The system uses the element type filter and EGR valve which recirculates exhaust gases during part throttle applications as before. However, to improve driveability, all California models use a two-stage EGR valve (one-stage in the 49 state models), and California models equipped with an automatic use an electric throttle valve switch to further limit exhaust gas recirculation to part throttle applications (EGR permitted only between 12ordm; to 72ordm; on a scale of 90ordm; throttle valve rotation).

The EGR system is installed on all 1975-80 models. All applications use the element-type filter and single-stage EGR valve. Recirculation occurs during part throttle applications as before. The system is controlled by a throttle valve switch, which measures throttle position, and an intake air sensor which reacts to engine vacuum. 1977 and later Type 1's destined for California are equipped with a mechanically operated EGR valve. A rod is attached to the throttle valve lever and operates the throttle position. No exhaust gases are recirculated at or near full throttle or at closed throttle. Beginning in 1975, an odometer actuated EGR reminder light (on the dashboard) is used to inform the driver that it is time to service the EGR system. The reminder light measures elapsed mileage and lights at 15,000 mile intervals. A reset button is located behind the switch.

Type 2 See Figures 3 and 4

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Fig. Fig. 3: Exhaust Gas Recirculation (EGR) system-1973 Type 2 models equipped with automatic transaxles



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Fig. Fig. 4: Exhaust Gas Recirculation (EGR) system-1974 Type 2 California models equipped with manual transaxles

Type 2 models use an EGR system beginning in 1973. All models use two valves; one at each manifold. Exhaust gas is taken from the muffler, cleaned in a replaceable-type filter, then directed to both intake manifolds, via the EGR valves. On models equipped with manual transaxles, recirculation is vacuum controlled and occurs both during part and full throttle applications. On models equipped with the automatic, recirculation is controlled both by throttle position and engine compartment (ambient) temperature. When the ambient temperature exceeds 54ordm; F, a sensor switch (located above the battery) opens, permitting EGR during part throttle applications.

All 1974 Type 2 models use the EGR system, but there are three different systems used. All models use one central EGR valve. Exhaust gas is taken from No. 4 exhaust port, cleaned in an element-type filter, and then directed to both intake manifolds via the single EGR valve. Models equipped with manual transaxles and sold in the 49 states use a single-stage EGR valve which allows recirculation according to the vacuum signal in the left carburetor during part throttle applications. Models equipped with manual transaxles and sold in California use a two-stage EGR valve which recirculates exhaust gases during part throttle openings in two steps. During the first stage, EGR is controlled by the vacuum in the left carburetor. The second stage controls EGR according to the throttle position of the right carburetor. Finally, all models equipped with automatic transaxles (nationwide) use a single-stage EGR valve which controls recirculation according to throttle valve position and engine cooling air temperature. When the cooling system air reaches 185ordm; F, a sensor switch (located between the coil and distributor) opens, permitting EGR during part throttle applications.

All 1975-81 Type 2 models utilize an EGR system. A single-stage EGR valve and element-type filter are used on all applications. Recirculation occurs during part throttle opening and is controlled by engine vacuum, throttle position and engine compartment temperature. At or near full throttle and when the throttle is closed, a solenoid is activated by the throttle valve switch which cuts off the vacuum supply and stops the recirculation of exhaust gases. At 15,000 mile intervals, a dash mounted EGR service reminder light is activated to warn the driver that EGR service is now due. A reset button is located behind the switch.

Type 3 See Figures 5 and 6

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Fig. Fig. 5: Exhaust Gas Recirculation (EGR) system-1972 Type 3 California models equipped with automatic transaxles



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Fig. Fig. 6: Exhaust Gas Recirculation (EGR) system-1973 Type 3 models equipped with automatic transaxles

EGR is first used in the 1972 Type 3 models destined for California and equipped with automatic transaxles. Exhaust gas is drawn from the front, right-hand exhaust flange to the EGR valve via a container and cyclone filter. The EGR valve then delivers the exhaust gases to the intake air distributor under part throttle (not full throttle or idling) conditions when the ambient air temperature reaches 65ordm; F and only first or second gears are selected.

All 1973 Type 3 models equipped with automatic transaxles use an EGR system. The exhaust gases are cleaned in a replaceable element-type filter in 1973 instead of the cyclone filter and container of the previous year. The EGR valve then delivers the gases according to an electromagnetic valve which permits recirculation above 54ordm; F.

Type 4 See Figure 7

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Fig. Fig. 7: Exhaust Gas Recirculation (EGR) system-1974 Type 4 models equipped with automatic transaxles

The EGR system appears only on 1974 models (nationwide) equipped with automatic transaxles. On this system, exhaust gas is drawn from the muffler to a single EGR valve via an element type filter. The gases are delivered to the intake air distributor under part throttle conditions.

EGR VALVE SERVICE



The EGR valve should be checked every 15,000 miles and the filter cleaned (cyclone-type) or replaced (element-type).

EGR VALVE INSPECTION



1972-74 Type 1 (Except 1974 California Models)

  1. With the engine idling at operating temperature (176ordm; F), pull off the vacuum hose from the EGR valve and push on the black hose from the intake air preheating thermostat instead.
  2.  
  3. If the idle speed drops off sharply or stalls, recirculation is taking place and the valve is OK. If, however, the idle speed does not change, the EGR valve is faulty or a hose is cracked or blocked.
  4.  
  5. Replace the vacuum hoses to their original locations.
  6.  

1974 Type 1 California and 1974 Type 2 Manual Transaxle California Models

On these 1974 California models, a two-stage EGR valve with a visible pin is used. To check the valve operation, simply make sure that the pin moves in and out relative to engine rpm. If the pin does not move, check the hoses and/or replace the EGR valve.

1975-80 Type 1 Except 1977 and Later California Models

  1. Start the engine and pull the electrical connector off the EGR valve vacuum unit (the disk-shaped unit located near the ignition coil).
  2.  
  3. This should make the engine slow down or stall, which means exhaust gases are being recirculated.
  4.  
  5. If no engine speed change occurs, stop the engine, then return the ignition key to the ON (not START ) position.
  6.  
  7. Connect a test light across the terminals of the connector cable, then move the throttle valve by hand from idle position to about mid-speed range.
  8.  
  9. If the test light goes OFF when the throttle is moved out of idle position, but lights at idle or full throttle position, replace the EGR valve.
  10.  
  11. If the test light does not light at all, there is probably trouble with the wiring or the throttle valve switch, which is located to the left of the alternator.
  12.  

Type 1 1977 and Later California Models

Remove the E-clip connecting the operating rod from the throttle to the EGR valve. Start the engine and allow it to idle. Manually operate the EGR valve: the engine should slow down or stop when the EGR valve is opened. If no speed change occurs, check the EGR pipe for clogging or replace the EGR valve.

ADJUSTING
  1. Idle the engine at 800-950 rpm.
  2.  
  3. Loosen both locknuts on the rod and shorten the length of the rod by turning it.
  4.  
  5. The idle should drop suddenly, indicating the EGR valve has opened. From this position lengthen the rod 1 1 / 2 turns (1 5 / 6 turns for 1979-80 models), using the pin in the center of the rod for orientation.
  6.  
  7. Tighten the locknuts.
  8.  

1973 Type 2

  1. Remove the EGR valve.
  2.  
  3. Inspect the valve for cleanliness.
  4.  
  5. Check the valve for freedom of movement by pressing in on the valve pin.
  6.  
  7. Connect the valve to the vacuum hose of another engine or vacuum source and start the engine. At 1,500-2,000 rpm the valve pin should be pulled in and when the speed is reduced it should return to its original position. Replace the EGR valve if it doesn't operate correctly.
  8.  
  9. Replace the washer and install the valve.
  10.  
  11. Repeat this operation on the second valve.
  12.  

1974 Type 2 With Manual Transaxle (Except California Models)

  1. With the engine idling at operating temperature, pull off the vacuum hose at the tee-fitting for the EGR valve and push on the hose from the flow valve of the air pump to the fitting instead.
  2.  
  3. If idle speed drops sharply or stalls, the valve is OK. If the rpm does not change, a hose is blocked or the valve is faulty.
  4.  
  5. Replace the hoses to their original locations.
  6.  

1975 and Later Type 2

This procedure is the same as 1975-80 Type 1 (Except 1977 and Later California models), except that the EGR valve is located approximately on top of No. 4 cylinder. A long feed pipe connects the EGR valve with the throttle valve housing. The throttle valve switch is located at the bottom of the throttle valve housing and is difficult to see without removing the housing. The switch is black, rectangular and has an electrical connector plugged into it.

1972-73 Type 3

  1. Remove the EGR valve.
  2.  
  3. Reconnect the vacuum hose and place the valve on the base.
  4.  
  5. Start the engine. If it doesn't stall, the vacuum line between the valve base and the intake manifold is clogged and must be cleaned.
  6.  
  7. Run the engine at 2,000-3,000 rpm. The closing pin of the EGR valve should pull in 0.15 in. (4 mm) and immediately return to its original position at idle. Replace the EGR valve if it doesn't operate correctly.
  8.  
  9. Install the EGR valve using new seals.
  10.  

1974 Type 4 Automatic Transmission

  1. Run the engine at idle.
  2.  
  3. At the EGR valve, disconnect the hose that runs to the throttle valve housing.
  4.  
  5. Disconnect the hose that runs to the idle speed regulator from the "T" pipe located in front of the intake manifold, and connect the hose from the EGR valve to the "T" pipe. Hold the idle speed regulator plunger back with your hand to prevent it from raising the idle speed.
  6.  
  7. If the engine speed drops or the engine stalls, the EGR valve is working. If nothing happens, either the EGR valve is defective or the lines are clogged.
  8.  

 
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