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heater core removal and replacement [message #341241]

Sat, 23 February 2019 17:17

sandy trout

Messages: 51
Registered: October 2018
Location: texas

Karma: 1

Member

78 GMC Royal drivers side kitchen and bath/separate shower, 403 c.i. engine
How does the heater core come out and is there an over the counter replacement that doesn't need modifications to fit?
I have seen some of these where they want $200 and a core returned. Anything cheaper?

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Re: heater core removal and replacement [message #341246 is a reply to message #341241]

Sat, 23 February 2019 19:26

Nicholls

Messages: 36
Registered: January 2008
Location: Pensacola, FL

Karma: 0

Member

I have one out of a 78 Royale for $50. Are you coming to Tallahassee?

John Nicholls, 78 Royale w/455 Pensacola, FL

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Re: heater core removal and replacement [message #341247 is a reply to message #341246]

Sat, 23 February 2019 21:11

sandy trout

Messages: 51
Registered: October 2018
Location: texas

Karma: 1

Member

No, we are not. Thanks for the offer.

It hasn't failed but got a lot of green staining around it and while redoing all the ac/heater motor and switches, thought I might change it out.
I saw in the parts list that Four Seasons # 94530 is suppose to work, but I don't know if it a drop in as I don't know the dimensions of the original or the suggested replacement. The inlet and outlets don't have the fancy turns in them like the original but they are bent in the same direction.
Just wondering if it is the same core dimension as the original or if that matters at all.
Then there is the problem of getting it out, does it come out from the outside or do you have to tear the dash apart to get it removed?

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Re: heater core removal and replacement [message #341248 is a reply to message #341247]

Sat, 23 February 2019 21:23

C Boyd

Messages: 2629
Registered: April 2006

Karma: 18

Senior Member

It does come out the front and any competent radiator repair facility should be able to clean and repair it.

sandy trout wrote on Sat, 23 February 2019 22:11

No, we are not. Thanks for the offer.

It hasn't failed but got a lot of green staining around it and while redoing all the ac/heater motor and switches, thought I might change it out.
I saw in the parts list that Four Seasons # 94530 is suppose to work, but I don't know if it a drop in as I don't know the dimensions of the original or the suggested replacement. The inlet and outlets don't have the fancy turns in them like the original but they are bent in the same direction.
Just wondering if it is the same core dimension as the original or if that matters at all.
Then there is the problem of getting it out, does it come out from the outside or do you have to tear the dash apart to get it removed?

C. Boyd
76 Crestmont
East Tennessee

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Re: heater core removal and replacement [message #341260 is a reply to message #341248]

Sun, 24 February 2019 11:58

Ty Hardiman

Messages: 43
Registered: April 2017
Location: Norman, Oklahoma

Karma: 0

Member

The heater core comes out from the front. There were three versions of the dash HVAC system but they all have the same procedure for your goal.

Here are pics of the heat & a/c box. It is under the "hood", actually dead center between the two hoods. You will need to remove heater hoses, windshield washer reservoir, anything else in the way to get to the cover of the box. The cover that you are removing can be identified by the "Harrison" sticker on it.
http://www.gmcmhphotos.com/photos/plenum/p14766.html
http://www.gmcmhphotos.com/photos/hvac-original-and-mods/p63542-1977-2f78-ac-box.html

A pic of the Harrison unit with the cover off, allowing access to the heater core:
http://www.gmcmhphotos.com/photos/plenum/p14771.html

A pic of the heater core:
http://www.gmcmhphotos.com/photos/dash-air-conditioning-redesign/p30759-slide10.html

Another link with good pics:
http://www.gmcmhphotos.com/photos/plenum/p14766.html

Ken Henderson's rebuild:
http://www.gmcmhphotos.com/photos/dash-air-conditioning-redesign/p30752-dash-air-conditioner-redesign.html

Ken was modifying the problematic 1975/1976 dash HVAC by drilling holes in the firewall. Your 1978 does not have this problem, simplifying your project.

Norman, OK / August 1977 Kingsley / 403 / 3.55 / 16" / Quadrajet

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Re: heater core removal and replacement [message #341278 is a reply to message #341260]

Sun, 24 February 2019 21:01

sandy trout

Messages: 51
Registered: October 2018
Location: texas

Karma: 1

Member

Thanks, the info and especially the pictures help a lot.
Glad to see something was modified to removed it easier, wish they would have done something like that for removing the brake booster.

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