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| [GMCnet] '78 heater line connections [message #303018] |
Sun, 03 July 2016 20:23  |
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mark grady
Messages: 70
Registered: November 2015
Location: northern Indiana
Karma: 0
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I'm working on final fitting this week of the interior. PO had added front
and rear extra heater cores, one under the passenger side bunk bed and one
tee'd off the water heater loop under the rear bed. Both were leaking. Both
are now removed until the next phase of the project.
I don't think the heater lines connecting the engine and the dash heater
core are correct.
The front heater core uses a 5/8 supply hose, and a 3/4" return. I don't
know if this is correct, but the heater core connectors are two different
sizes.
Here is my assumption. When correct - the heater supply line is from the
passenger rear intake manifold threaded fitting, which on many Olds engines
had a vacuum operated heater control valve. The GMC does not.
The return line is connected to the fitting on the water pump that faces
the AC compressor on the passenger side of the engine.
My question: Is the rear water heater pre-heat tee'd into both the heater
core lines, or is it in series with the return side of the heater core?
An answer or a reference to the page in one of the manuals is appreciated.
Mark Grady
'78 Kingsley
N.IN
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'77 + 78 Kingsley
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| Re: [GMCnet] '78 heater line connections [message #303022 is a reply to message #303018] |
Sun, 03 July 2016 21:54  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Mark,
The heater hoses are, indeed, 5/8" and 3/4". The water heater connections
are tee'd into both the supply and return lines for the cockpit heater.
That is, the two heaters are connected in parallel, not series.
HTH,
Ken H.
On Sun, Jul 3, 2016 at 9:23 PM, mark grady wrote:
> I'm working on final fitting this week of the interior. PO had added front
> and rear extra heater cores, one under the passenger side bunk bed and one
> tee'd off the water heater loop under the rear bed. Both were leaking. Both
> are now removed until the next phase of the project.
>
> I don't think the heater lines connecting the engine and the dash heater
> core are correct.
>
> The front heater core uses a 5/8 supply hose, and a 3/4" return. I don't
> know if this is correct, but the heater core connectors are two different
> sizes.
>
> Here is my assumption. When correct - the heater supply line is from the
> passenger rear intake manifold threaded fitting, which on many Olds engines
> had a vacuum operated heater control valve. The GMC does not.
>
> The return line is connected to the fitting on the water pump that faces
> the AC compressor on the passenger side of the engine.
>
> My question: Is the rear water heater pre-heat tee'd into both the heater
> core lines, or is it in series with the return side of the heater core?
>
> An answer or a reference to the page in one of the manuals is appreciated.
>
> Mark Grady
> '78 Kingsley
>
> N.IN
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] '78 heater line connections [message #303023 is a reply to message #303022] |
Sun, 03 July 2016 22:13 |
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mark grady
Messages: 70
Registered: November 2015
Location: northern Indiana
Karma: 0
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Ken -
Thanks so much. I found that detail on page 100 and 101 of the assembly
manual, and even had enough parts, hoses and clamps to get everything put
together!
I would have added a shutoff valve for the front heater core, but I didn't
have one, I can put it in very easily when I get one.
On Sun, Jul 3, 2016 at 10:54 PM, Ken Henderson
wrote:
> Mark,
>
> The heater hoses are, indeed, 5/8" and 3/4". The water heater connections
> are tee'd into both the supply and return lines for the cockpit heater.
> That is, the two heaters are connected in parallel, not series.
>
> HTH,
>
> Ken H.
>
>
> On Sun, Jul 3, 2016 at 9:23 PM, mark grady wrote:
>
>> I'm working on final fitting this week of the interior. PO had added
> front
>> and rear extra heater cores, one under the passenger side bunk bed and
> one
>> tee'd off the water heater loop under the rear bed. Both were leaking.
> Both
>> are now removed until the next phase of the project.
>>
>> I don't think the heater lines connecting the engine and the dash heater
>> core are correct.
>>
>> The front heater core uses a 5/8 supply hose, and a 3/4" return. I don't
>> know if this is correct, but the heater core connectors are two different
>> sizes.
>>
>> Here is my assumption. When correct - the heater supply line is from the
>> passenger rear intake manifold threaded fitting, which on many Olds
> engines
>> had a vacuum operated heater control valve. The GMC does not.
>>
>> The return line is connected to the fitting on the water pump that faces
>> the AC compressor on the passenger side of the engine.
>>
>> My question: Is the rear water heater pre-heat tee'd into both the heater
>> core lines, or is it in series with the return side of the heater core?
>>
>> An answer or a reference to the page in one of the manuals is
> appreciated.
>>
>> Mark Grady
>> '78 Kingsley
>>
>> N.IN
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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'77 + 78 Kingsley
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| Re: [GMCnet] '78 heater line connections [message #303024 is a reply to message #303023] |
Sun, 03 July 2016 22:24 |
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mark grady
Messages: 70
Registered: November 2015
Location: northern Indiana
Karma: 0
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Member |
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And a big thanks to Bob Burkitt, he included some pix in a direct e-mail,
and what do you know - there is a vacuum operated heater core valve hidden
by the washer tank. So I'll get some 5/8" line and take out one extra
splice tomorrow.
Answers in less than an hour. That's professional grade!
I should have taken a pic of how this was done before I started, but it was
not good. I did add a shutoff valve for the water heater engine loop, which
is opened when the control is in the defroster setting. This helps
eliminate heat build up in the bathroom.
Thanks all,
Mark Grady
'78 Kingsley (Bucky) in Northern Indiana (N.IN)
On Sun, Jul 3, 2016 at 11:13 PM, mark grady wrote:
> Ken -
>
> Thanks so much. I found that detail on page 100 and 101 of the assembly
> manual, and even had enough parts, hoses and clamps to get everything put
> together!
>
> I would have added a shutoff valve for the front heater core, but I didn't
> have one, I can put it in very easily when I get one.
>
> On Sun, Jul 3, 2016 at 10:54 PM, Ken Henderson
> wrote:
>
>> Mark,
>>
>> The heater hoses are, indeed, 5/8" and 3/4". The water heater connections
>> are tee'd into both the supply and return lines for the cockpit heater.
>> That is, the two heaters are connected in parallel, not series.
>>
>> HTH,
>>
>> Ken H.
>>
>>
>> On Sun, Jul 3, 2016 at 9:23 PM, mark grady wrote:
>>
>>> I'm working on final fitting this week of the interior. PO had added
>> front
>>> and rear extra heater cores, one under the passenger side bunk bed and
>> one
>>> tee'd off the water heater loop under the rear bed. Both were leaking.
>> Both
>>> are now removed until the next phase of the project.
>>>
>>> I don't think the heater lines connecting the engine and the dash heater
>>> core are correct.
>>>
>>> The front heater core uses a 5/8 supply hose, and a 3/4" return. I don't
>>> know if this is correct, but the heater core connectors are two
>> different
>>> sizes.
>>>
>>> Here is my assumption. When correct - the heater supply line is from
>> the
>>> passenger rear intake manifold threaded fitting, which on many Olds
>> engines
>>> had a vacuum operated heater control valve. The GMC does not.
>>>
>>> The return line is connected to the fitting on the water pump that faces
>>> the AC compressor on the passenger side of the engine.
>>>
>>> My question: Is the rear water heater pre-heat tee'd into both the
>> heater
>>> core lines, or is it in series with the return side of the heater core?
>>>
>>> An answer or a reference to the page in one of the manuals is
>> appreciated.
>>>
>>> Mark Grady
>>> '78 Kingsley
>>>
>>> N.IN
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
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'77 + 78 Kingsley
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| Re: [GMCnet] '78 heater line connections [message #303029 is a reply to message #303026] |
Sun, 03 July 2016 23:25 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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The problem with those vacuum actuated heater control valves is they do not completely close off the hot coolant flow. I have that vacuum controlled valve and an added ball valve in series. In the spring or summer I turn off the ball valve to completely block all coolant flow. If I ever need the flow again, it a simple 10 second fix to make it operational again. My ball valve is located under the passenger side hood near the heater core.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] '78 heater line connections [message #303038 is a reply to message #303029] |
Mon, 04 July 2016 05:40 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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Another vote for Ken's method. Since we need cool air in Lower Alabama, not having any heated water in the core is a definite goal. I also put ball joints in the lines to the hot water in the rear. If I ever want to use that method to produce hot water, it is simple to open the valve.
Having lost one engine to a blown line to the rear, I'm sensitive to that failure.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] '78 heater line connections [message #303060 is a reply to message #303038] |
Mon, 04 July 2016 15:15 |
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mark grady
Messages: 70
Registered: November 2015
Location: northern Indiana
Karma: 0
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Member |
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After finding the hidden vacuum heater control shutoff valve, it's in
pretty good shape on the outside, but the seal on the inside is real spongy
looking, and the actuator shaft is a little leaky.
So I'll replace it now instead of when I have to. The one I have doesn't
look anything like a GM valve, more like a FOMOCo or VW / Audi valve.
Just trying different searches, the closest is a Murray 74671, a metal
banded top and plastic outlet with a metal diaphragm housing.'78
Tomorrow, more parts, I may have my other questions (oil sender and temp
sender) answers by then too.
Mark Grady, Northern Indiana
'78 Kingsley
On Mon, Jul 4, 2016 at 6:40 AM, Thomas Phipps wrote:
> Another vote for Ken's method. Since we need cool air in Lower Alabama,
> not having any heated water in the core is a definite goal. I also put ball
> joints in the lines to the hot water in the rear. If I ever want to use
> that method to produce hot water, it is simple to open the valve.
> Having lost one engine to a blown line to the rear, I'm sensitive to that
> failure.
> Tom, MS II
> --
> 1975 GMC Avion
> KA4CSG
>
> _______________________________________________
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'77 + 78 Kingsley
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| Re: [GMCnet] '78 heater line connections [message #303062 is a reply to message #303060] |
Mon, 04 July 2016 16:46 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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mark grady wrote on Mon, 04 July 2016 16:15After finding the hidden vacuum heater control shutoff valve, it's in pretty good shape on the outside, but the seal on the inside is real spongy looking, and the actuator shaft is a little leaky.
So I'll replace it now instead of when I have to. The one I have doesn't look anything like a GM valve, more like a FOMOCo or VW / Audi valve.
Just trying different searches, the closest is a Murray 74671, a metal banded top and plastic outlet with a metal diaphragm housing.'78
Tomorrow, more parts, I may have my other questions (oil sender and temp sender) answers by then too.
Mark Grady, Northern Indiana
'78 Kingsley
Mark,
There are no valves out there that look like the OE, almost anything will work there if it is - VACUUM TO CLOSE.
They come both V to C and V to O. Be sure to get the correct one. If in doubt, go and get a PEX ball valve a Lowe Depot and some hose clamps to get by.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] '78 heater line connections [message #303213 is a reply to message #303062] |
Thu, 07 July 2016 09:19 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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Mark,
The original valve PN#494192 listed in 78Z parts book on page 26-15 is obsolete, difficult if not impossible to find. If you go to the GMCMH Parts Interchange Index which is now available to all you can go to the Heater & Air Conditioning section and look in the HEATER section and down under the Temp valve section there are 12 replacement valves listed. All you have to do is sign up for access to interchange which is FREE! The Motorcraft part# YG136 from O’Reilly’s which you reference is available but cost 2X to 3X more of the valves on the GMCMI list. I personally have used the P# 74612 which is available from many of the Big Box Autoparts store for around $10 give or take.
http://www.gmcmi.com
JR Wright
GMC Great Laker MHC
GMC Eastern States Charter Member
GMCGL Tech Editor
GMCMI
78 GMC Buskirk 30’ Stretch
1975 GMC Avion (Under Reconstruction)
Michigan
> On Jul 4, 2016, at 5:46 PM, Matt Colie wrote:
>
> mark grady wrote on Mon, 04 July 2016 16:15
>> After finding the hidden vacuum heater control shutoff valve, it's in pretty good shape on the outside, but the seal on the inside is real spongy
>> looking, and the actuator shaft is a little leaky.
>>
>> So I'll replace it now instead of when I have to. The one I have doesn't look anything like a GM valve, more like a FOMOCo or VW / Audi valve.
>>
>> Just trying different searches, the closest is a Murray 74671, a metal banded top and plastic outlet with a metal diaphragm housing.'78
>> Tomorrow, more parts, I may have my other questions (oil sender and temp sender) answers by then too.
>>
>> Mark Grady, Northern Indiana
>> '78 Kingsley
>
> Mark,
>
> There are no valves out there that look like the OE, almost anything will work there if it is - VACUUM TO CLOSE.
> They come both V to C and V to O. Be sure to get the correct one. If in doubt, go and get a PEX ball valve a Lowe Depot and some hose clamps to get
> by.
>
> Matt
> --
> Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
> '73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
> Now with both true Keyless and remote entry
> SE Michigan - Twixt A2 and Detroit
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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