Working on replacing my heater core. I have removed the entire lower dash. I located three mounting screws for the heater box, info I have found says there should be one more hidden behind a plastic cap.
I can see what I think must be the fourth screw, but can't figure out how to remove the cap. It is near impossible to get to.
Where do I go from here? Does the upper dash pad need to be removed, and if so how does it come out?
I have a Fisher Body service manual on the way. Will it give the step by step I need to complete the job?
Did a search for threads on here and found little that was specific enough to be much help.
All advice appreciated.

 

Do you have a 1976 Olds factory Chassis Service Manual? The heater core R&R info is in it.

 

Yes I do have the chassis manual. All it told me was the location of the bolts, not how to access them.
I did find directions to remove the upper dash pad, will try that tomorrow and see if it gives me access to that hidden fastener.

 

Ok folks, the end of the story for future reference.
After tearing apart my entire dash in search of the mystery plastic covered bolt, I found out it doesn't exist.
Instead there are 3 more speed nut fasteners on the outside of the fire wall. Two are to the driver side of the heater core tubes, and one is on the A/C housing.
All went fine after that discovery. Heater core should come out with just the removal of the lower dash trim and glove box. I cannot verify this because I had already removed the entire dash.