4.3 engine - front of motor above water pump
The 1997 Chevrolet Astro EGR valve is located on the top of the engine valve cover. The EGR valve can be access from under the hood. You will not need to remove any engine cover.
directly under throttle body
figuratively yes but unadvisable
It is under the air cleaner system, on the front of the engine.
700R4 transmission.
The 1987 Chevrolet Astro turn signal relay switch can be found beneath the drivers side dashboard. The turn signal relay switch will be above the gas pedal.
egr wire connection
You have to remove the fuel tank to get at it.
27 gallons
Ther is no egr valve on the 2.2 turbo engines. With FI and turbo, there was no need. Some of the earlier carb engines did have egr.
Remove the water supply hose from your 1987 Chevy Astro thermostat housing. Remove the thermostat housing retaining bolts. Remove the old thermostat and drive in the new thermostat.
That could be cause by a worn out rubber grommet that surrounds the EGR valve. Or possibly the EGR valve may not be pushed in all the way.