A. USA Model Year 1980

A. USA model year 1980






Testing EGR




Connect vacuum tester between EGR valve (60) and switchover valve (64b) to vacuum line (white/purple/brown). At idle, with throttle linkage at idle stop, no vacuum should be indicated. Advance control linkage until free travel of free travel rod is eliminated (do not pull on stop lever). Vacuum should now amount to 350-500 mbar.

If:
- vacuum nominal value of 350-500 mbar is attained. Proceed to "Checking EGR valve (60)" (below).
- vacuum nominal value is not attained or exceeded. Continue with "Check vacuum lines".

Check vacuum lines




Check all vacuum lines for control of EGR system and of automatic transmission according to operational diagram vacuum line layout for correct connection and leaks. Blow through orifice (62) at vacuum tapping point.




Check black vent line (arrow) from vacuum control valve to passenger compartment for free passage.


Check thermovalve 40°C / 104°F (36, color code blue)




Pull off vacuum line (white/purple/brown) on diagonal connection of thermovalve.

Check vacuum line (white/brown) on distributor (a) and check for passage. If there is no passage, replace thermovalve.

When thermovalve is cooling down, thermovalve should have no passage at temperatures below 7 °C/45 °F.


Check switchover valve (64a)

Pull connection (arrow) of vacuum line (white/purple/brown) from switchover valve.

Connect vacuum tester to free connection of switchover valve and connect with pulled off vacuum line. Vacuum readout approx 350-500 mbar (regulating linkage at idle speed stop).


Leak test




Disconnect distributor of white/purple/ brown vacuum line.

Vacuum should remain constant for approx. 2 minutes.

If vacuum drops, replace switchover valve.




If vacuum remains constant, check switchover:

For this purpose, remove clamp, pull off connecting hose between the two switch- over valves and bridge free travel on free travel rod.

Vacuum should distinctly drop. If vacuum is not dropping, replace switchover valve.


Checking switchover valve (64b)




Pull off vacuum line (white) on switchover valve (64b). Pull off vacuum line (white/purple/brown) on switchover valve (64a). Connect vacuum tester to free connection of switchover valve (64b) and connect with pulled off vacuum line (white/purple/brown). Vacuum readout 350-500 mbar.


Leak test




For this purpose, disconnect distributor of vacuum line (white/purple/brown). Vacuum should remain constant for approx. 2 minutes.

If vacuum drops, replace switchover valve.

If vacuum remains constant, check switchover:




For this purpose, remove clamp and pull off vacuum line (white/purple/brown) on switchover valve (64b). Switch over switch- over valve with screwdriver. Vacuum should drop to "0".

If vacuum is not dropping to "0", replace switchover valve.


Checking EGR valve (60)




Switch over switchover valve (64a) by bridging free travel "L" on free travel rod. Pull off vacuum line on EGR valve and plug on again.

EGR valve should audibly close.

If EGR valve not closing.




Replace EGR valve (60).


Checking vacuum control




Connect vacuum tester to vacuum line between EGR valve (60) and switchover valve (64b). Increase idle speed to 1000 ± 10/min by operating regulating linkage (do not pull on stop lever)

If vacuum amounts to 320-350 mbar. Testing is complete.

If vacuum is below or above specified value.


Check orifice (63)




Check if orifice is open and blow through, if required.


Change orifice (63)

If the vacuum is not attained or is exceeded, install the next larger size orifice, if the vacuum is too high and the next smaller orifice if the vacuum is too low.

If the correct vacuum is not attained by the installation of another orifice, replace vacuum control valve (65).

End of test