Jay:

The switchover valves for the EGR and air recirc valve (on the turbo) are under the air filter on the passenger side, down by the turbo.

There are four vacuum lines from the accessory connection on the 603 -- a five way connection right up front just behind the rad. Two go off to the climate control and transmission system on the driver's side and the other two go to the swithover valves.

The best way to check them all out is to get a MitiVac hand pump -- you can then pull one line at a time off and insert the rubber fitting on the pump into the line and pump -- if it won't hold vacuum, something is wrong. There are some vacuum storage tanks in the system that can take a number of pumps to evacuate, so don't assume a system is bad until you have operated the pump several strokes.

Other than the switchover valves, check all the rubber parts of the vacuum lines -- they get old and soft (and sticky) or rock hard, and in either case leak (sometimes the soft ones will collapse, too). Replace any that are iffy with standard vacuum line from the autoparts store. Make sure you don't lose any white or yellow "butt connectors" present -- these are restrictors and must be replaced into the original position.

The transmission control circuit is somewhat complicated -- I have a diagram I can copy and mail you if you need it.

Most likely you have dead switchover valves or a leaking connection someplace -- the rubber is the correct age to fail! Sorry to say, the usual problem with the switchover valves is a failed valve, not leaking connectors.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!