There is a sensor that screws onto the thermostat housing.

There are 2 nipples on this sensor, both for connecting vacuum lines. One vacuum line comes from the back box on the valve cover. The other vacumm line goes to the EGR valve.

I replaced the sensor and need to ascertain which nipple connects to which side.

Looking at the sensor, it says CARB on one side.

Any help would be appreciated.

You would be well advised to ignore all of the vacuum lines running to that sensor beacuse you do NOT want to run EGR unless you absolutely have to for government inspection. The vacuum from the black box goes to the sensor, which is a coolant switch, and then onto the EGR valve. The coolant switch blocks the vacuum from the black box until the engine gets up to a sufficient temperature (50 C. ??). Then the sensor opens and allows vacuum to go to the EGR valve.

You can plug the vacuum from the black box and igonore all of the lines to the sensor and onto the valve itself.

I fact, I still have a couple of kits left over that will allow you to remove the valve completely and replace it with a stainless steel plate (for testing purposes )

It's a simple switch so I don't think it matters which nipple connects to which hose. Typically, though, the tilted nipple connects to the vacuum source and the straight nipple connects to the EGR valve.

Sixto
95 S420
87 300SDL

Thanks guys!

Appreciate the help. Good point about the not messing with the switch.

Please let me know about the 'kit' to replace the switch.

Thanks again.