The question you ask is too involved for a proper answer. you need to go to a car parts store, and get you a repair manual for your car. They cost about $16.00.
I have one. Want it?
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There is NOT an EGR valve on this engine.
How do you replace an 1994 3.1 Oldsmobile Achieva s radiator?
4x6 in the front 6x9 in the back
If you need to know that. You should not be behind the wheel.
Under the dash on the left side of the steering column/
to the left of the right rear tire It'son the front of the gas tank.
On my 93 it is under the kick panel under the dash on the passenger side. Fairly easy to get to.
It is about a 3 hour job. It would depend on the hourly charge of your local shop, plus the cost of the heater core. Which I think is around 30 bucks.
How do you change a heater core in 1994 chevy astro van?
Put a potato in the exhaust pipe.