The question you ask is too involved for a proper answer. you need to go to a car parts store, and get a repair manual for your car. They cost about $16.00
I have replaced a heater core in this style of truck. The manual calls for removing the entire dash. I was able to take out the screws under the dash... but a few of the top screws on the duct will require a flexible screwdriver. I removed all but two screws and yanked, breaking the duct gaining access to the heater core. Luckily the reinstallation of the broken duct was perfect, no leaks. This method saves alot of time and headache. The entire dash is not easily removed and reinstalled.
replace heater core in a 1991 Chevy work truck 1500
It is possible but takes a while. Get a manual on your car from the parts store or DISCOUNTAUTOREPAIRMANUALS.COM
replace or repair. It will only get worse.
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diagram for a 92 Chevy van g20 Heater core
1991 Chevy s10 how to replace outside window weather strip
I recently installed a new heater core in a 1991 G10 van. I removed the heater fan housing, the heater core hoses, then the compartment came out. After removing the campartment has to be taken apart to replace the core. Alot of work but not all that hard.
How to remove and install the serpentine belt on 1991 Chevy Blazer with AC?
50 to 60 lbs
You do not need to completely remove the dashboard in order to change the heater core. Remove the water hoses from the heater core. Remove the heater core retaining bolts. Reverse the process to install the new heater core.