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| Heater core, which way does the coolant flow [message #172798] |
Sun, 10 June 2012 12:37  |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
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My thermostat is sticking open, so I'm installing a new one today.
While I'm at it, I want to install a shutoff valve on the heater core. The valve I has shows a coolant flow arrow for direction on it, but I don't know which hose is coming and going.
One hose is larger (3/4" I believe) and goes to the waterpump. The second hose is smaller (5/8") and goes to the T connection at the back passenger side of the intake.
Anyone know which is which?
I'm thinking the larger is the hot going to the heater just looking at the construction of the water pump and my farmboy knowledge of centrifugal pump operation.
Thanks
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| Re: Heater core, which way does the coolant flow [message #172810 is a reply to message #172798] |
Sun, 10 June 2012 14:02  |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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| rf_burns wrote on Sun, 10 June 2012 12:37 |
My thermostat is sticking open, so I'm installing a new one today.
While I'm at it, I want to install a shutoff valve on the heater core. The valve I has shows a coolant flow arrow for direction on it, but I don't know which hose is coming and going.
One hose is larger (3/4" I believe) and goes to the waterpump. The second hose is smaller (5/8") and goes to the T connection at the back passenger side of the intake.
Anyone know which is which?
I'm thinking the larger is the hot going to the heater just looking at the construction of the water pump and my farmboy knowledge of centrifugal pump operation.
Thanks
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Bruce,
I actually think the flow is from the back of the intake manifold towards the heater and the house water heater if you have that option.
Maintenance manual section 6K figure 4 shows the flow.
There is a restrictor in the fitting into the manifold that was intended to avoid the loss of too much engine heat.
You might consider putting a valve in both lines -- the heater core has been known to develop a leak at the worst times -- then you could isolate the heater if necessary.
Dennis
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: Heater core, which way does the coolant flow [message #172857 is a reply to message #172798] |
Sun, 10 June 2012 21:15 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Bruce,
The coolant leaves the top of the intake manifold travels through heater core and returns to the front of the engine (water pump).
I used a ball valve from the local hardware store (Lowes, Home Depot, etc.) for that function. I do not know the store brands in Canada. I do not think a ball valve is directional. You can put the valve in either line. There need to be a continuous flow of coolant through the intake manifold even when the thermostat is closed so the OEM valve had a intentional leak built into it to preserve some coolant flow. Installing a positive shut off like a ball valve is not a problem as long as you still have the water heater loop operational to circulate some of the coolant.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Heater core, which way does the coolant flow [message #172859 is a reply to message #172798] |
Sun, 10 June 2012 21:16 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Bruce,
I don't know which is which but below is a link to a picture of where the
shutoff valve is installed on Double Trouble.
I know it's a lousy picture as it's not clear which hose it's in (3/4" or
5/8") but I searched the Photo Site and it's the only one I could find.
www.gmcmhphotos.com/photos/member-galleries/p39553-battery-switches.html
It does look like it goes into the 5/8" line and logically I would have tie
wrapped them together so that the upper hose goes to the upper fitting as
they enter the heater box.
On top of all the above I can't remember if I installed it or if it was
installed by the PO!t it!
Not much help, eh?
Regards,
Rob M.
-----Original Message-----
From: Bruce Hislop
My thermostat is sticking open, so I'm installing a new one today.
While I'm at it, I want to install a shutoff valve on the heater core. The
valve I has shows a coolant flow arrow for direction on it, but I don't know
which hose is coming and going.
One hose is larger (3/4" I believe) and goes to the waterpump. The second
hose is smaller (5/8") and goes to the T connection at the back passenger
side of the intake.
Anyone know which is which?
I'm thinking the larger is the hot going to the heater just looking at the
construction of the water pump and my farmboy knowledge of centrifugal pump
operation.
Thanks
Bruce
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: Heater core, which way does the coolant flow [message #172866 is a reply to message #172857] |
Sun, 10 June 2012 21:47 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Ken,
I don't understand your comment that the water heater loop still needs to be operational.
Are you referring to the bypass from the thermostat housing to the water pump?
Thank you,
Dennis
| Ken Burton wrote on Sun, 10 June 2012 21:15 |
Bruce,
The coolant leaves the top of the intake manifold travels through heater core and returns to the front of the engine (water pump).
I used a ball valve from the local hardware store (Lowes, Home Depot, etc.) for that function. I do not know the store brands in Canada. I do not think a ball valve is directional. You can put the valve in either line. There need to be a continuous flow of coolant through the intake manifold even when the thermostat is closed so the OEM valve had a intentional leak built into it to preserve some coolant flow. Installing a positive shut off like a ball valve is not a problem as long as you still have the water heater loop operational to circulate some of the coolant.
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: Heater core, which way does the coolant flow [message #172883 is a reply to message #172866] |
Sun, 10 June 2012 22:44 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Dennis S wrote on Sun, 10 June 2012 21:47 |
Ken,
I don't understand your comment that the water heater loop still needs to be operational.
Are you referring to the bypass from the thermostat housing to the water pump?
Thank you,
Dennis
| Ken Burton wrote on Sun, 10 June 2012 21:15 |
Bruce,
The coolant leaves the top of the intake manifold travels through heater core and returns to the front of the engine (water pump).
I used a ball valve from the local hardware store (Lowes, Home Depot, etc.) for that function. I do not know the store brands in Canada. I do not think a ball valve is directional. You can put the valve in either line. There need to be a continuous flow of coolant through the intake manifold even when the thermostat is closed so the OEM valve had a intentional leak built into it to preserve some coolant flow. Installing a positive shut off like a ball valve is not a problem as long as you still have the water heater loop operational to circulate some of the coolant.
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No, I'm talking about the fitting on the rear of the intake manifold that normally feeds the heater and hot water heater. That coolant circulation is needed to provide coolant flow through the heads. The circulation path is normally through the water heater in the rear and the cabin heater up front in parallel. If you block (turn off) both of these you have a coolant flow problem through the engine heads.
This why the vacuum controlled heater valve up front only reduces the flow and does not completely turn it off. Just look inside one at the butterfly and you will see what I am talking about. This valve is not a problem on a GMC because of the alternate parallel path through the water heater. It is an issue when this engine is used in Oldsmobiles.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Heater core, which way does the coolant flow [message #172920 is a reply to message #172883] |
Mon, 11 June 2012 10:14 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Ken,
Thank you for the explanation.
I am going to look at my system again.
I do not have the water heater option. The heater supply is via a 5/8 inch hose from the outlet at the rear of the intake manifold. That outlet fitting has a restrictor -- approx 1/4 inch opening. The vacuum valve for the heater supply shut off is a Ready Aire, which cuts off the supply completely. The return line is 3/4 inch back to the water pump.
http://www.gmcmhphotos.com/photos/73-painted-desert-230/p30899-gmc-motorhome-009.html
Dennis
| Ken Burton wrote on Sun, 10 June 2012 22:44 |
| Dennis S wrote on Sun, 10 June 2012 21:47 |
Ken,
I don't understand your comment that the water heater loop still needs to be operational.
Are you referring to the bypass from the thermostat housing to the water pump?
Thank you,
Dennis
| Ken Burton wrote on Sun, 10 June 2012 21:15 |
Bruce,
The coolant leaves the top of the intake manifold travels through heater core and returns to the front of the engine (water pump).
I used a ball valve from the local hardware store (Lowes, Home Depot, etc.) for that function. I do not know the store brands in Canada. I do not think a ball valve is directional. You can put the valve in either line. There need to be a continuous flow of coolant through the intake manifold even when the thermostat is closed so the OEM valve had a intentional leak built into it to preserve some coolant flow. Installing a positive shut off like a ball valve is not a problem as long as you still have the water heater loop operational to circulate some of the coolant.
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No, I'm talking about the fitting on the rear of the intake manifold that normally feeds the heater and hot water heater. That coolant circulation is needed to provide coolant flow through the heads. The circulation path is normally through the water heater in the rear and the cabin heater up front in parallel. If you block (turn off) both of these you have a coolant flow problem through the engine heads.
This why the vacuum controlled heater valve up front only reduces the flow and does not completely turn it off. Just look inside one at the butterfly and you will see what I am talking about. This valve is not a problem on a GMC because of the alternate parallel path through the water heater. It is an issue when this engine is used in Oldsmobiles.
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Heater core, which way does the coolant flow [message #172927 is a reply to message #172920] |
Mon, 11 June 2012 10:37 |
Kosier
Messages: 834
Registered: February 2008
Karma: 1
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Senior Member |
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Dennis,
Don't worry about it. The left bank of the motor gets along just fine
without any bypass coming out the back.
Race cars, jet boats and irrigation pumpers and, who knows what else, get
along without it.
Gary Kosier
-----Original Message-----
From: Dennis Sexton
Sent: Monday, June 11, 2012 11:14 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Heater core, which way does the coolant flow
Ken,
Thank you for the explanation.
I am going to look at my system again.
I do not have the water heater option. The heater supply is via a 5/8 inch
hose from the outlet at the rear of the intake manifold. That outlet fitting
has a restrictor -- approx 1/4 inch opening. The vacuum valve for the heater
supply shut off is a Ready Aire, which cuts off the supply completely. The
return line is 3/4 inch back to the water pump.
http://www.gmcmhphotos.com/photos/73-painted-desert-230/p30899-gmc-motorhome-009.html
Dennis
Ken Burton wrote on Sun, 10 June 2012 22:44
> Dennis S wrote on Sun, 10 June 2012 21:47
> > Ken,
> >
> > I don't understand your comment that the water heater loop still needs
> > to be operational.
> > Are you referring to the bypass from the thermostat housing to the water
> > pump?
> >
> > Thank you,
> > Dennis
> >
> >
> > Ken Burton wrote on Sun, 10 June 2012 21:15
> > > Bruce,
> > >
> > > The coolant leaves the top of the intake manifold travels through
> > > heater core and returns to the front of the engine (water pump).
> > >
> > > I used a ball valve from the local hardware store (Lowes, Home Depot,
> > > etc.) for that function. I do not know the store brands in Canada. I
> > > do not think a ball valve is directional. You can put the valve in
> > > either line. There need to be a continuous flow of coolant through
> > > the intake manifold even when the thermostat is closed so the OEM
> > > valve had a intentional leak built into it to preserve some coolant
> > > flow. Installing a positive shut off like a ball valve is not a
> > > problem as long as you still have the water heater loop operational to
> > > circulate some of the coolant.
>
>
> No, I'm talking about the fitting on the rear of the intake manifold that
> normally feeds the heater and hot water heater. That coolant circulation
> is needed to provide coolant flow through the heads. The circulation path
> is normally through the water heater in the rear and the cabin heater up
> front in parallel. If you block (turn off) both of these you have a
> coolant flow problem through the engine heads.
>
> This why the vacuum controlled heater valve up front only reduces the flow
> and does not completely turn it off. Just look inside one at the
> butterfly and you will see what I am talking about. This valve is not a
> problem on a GMC because of the alternate parallel path through the water
> heater. It is an issue when this engine is used in Oldsmobiles.
--
Dennis S
73 Painted Desert 230
Germantown, TN
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| Re: Heater core, which way does the coolant flow [message #172930 is a reply to message #172928] |
Mon, 11 June 2012 10:46 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Don,
Thank you -- that was as found. Being slow at my projects the wall is still out and awaitng the repair of the wheel well before it goes back in....
another example of how one thing leads to another.
Dennis
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Heater core, which way does the coolant flow [message #172932 is a reply to message #172927] |
Mon, 11 June 2012 11:03 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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| Kosier wrote on Mon, 11 June 2012 10:37 |
Dennis,
Don't worry about it. The left bank of the motor gets along just fine
without any bypass coming out the back.
Race cars, jet boats and irrigation pumpers and, who knows what else, get
along without it.
Gary Kosier
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Thanks Gary,
I agree, but found my understanding of the system to be different than what was posted -- so, trying to remain open I thought I would look again.
Dennis
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Heater core, which way does the coolant flow [message #173059 is a reply to message #173057] |
Tue, 12 June 2012 07:00 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Bruce,
Head to Home Depot and get one like this; a couple of barbs, and two
stainless steel screw clamps.
www.homedepot.ca/product/ball-valve-3-4-inch-threaded-chrome-plated-brass-fu
ll-port/984070
Regards,
Rob M.
-----Original Message-----
From: Bruce Hislop
Well, I never did did my heater shut off valve in installed. Pager went off
and my whole plans for the day changed.
Anyway, looks like from the posting some type of bypass valving arrangement
would satisfy all the requirements. I looked on-line and all I can find is
industrial duty valves.. $$$$$.
Bruce
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: Heater core, which way does the coolant flow [message #173064 is a reply to message #173057] |
Tue, 12 June 2012 08:18 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Bruce,
Here is one style of heater shut off valve -- takes very little room and comes sized for different hose, ie, 1/2 or 3/5 inch.
http://www.amazon.com/Four-Seasons-84706-Shut-Valve/dp/B000CNJ66E
Dennis
| rf_burns wrote on Tue, 12 June 2012 06:35 |
Well, I never did did my heater shut off valve in installed. Pager went off and my whole plans for the day changed.
Anyway, looks like from the posting some type of bypass valving arrangement would satisfy all the requirements. I looked on-line and all I can find is industrial duty valves.. $$$$$.
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: Heater core, which way does the coolant flow [message #173065 is a reply to message #172798] |
Tue, 12 June 2012 09:22 |
Gary Mau
Messages: 152
Registered: February 2004
Location: Davenport, Iowa
Karma: 0
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Senior Member |
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I'm still a bit confused. The long standing recommendation to replace the vacuum operated heater shut-off valve with a manual valve would only apply to coaches with the water heater loop and not those that do not have that due to the need for a bypass?
Gary Mau
Former 76 Royale owner
Davenport, IA
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| Re: [GMCnet] Heater core, which way does the coolant flow [message #173068 is a reply to message #173064] |
Tue, 12 June 2012 09:34 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Since I very rarely need a heater, I haven't done this to the GMC but
would if I needed to frequently switch between heat and cool: The
GMC's water shutoff is a one-line control. Any leakage by that valve
is undesirable. A more effective control is an "H-valve", which
controls flow in both lines and, when closed, routes input flow back
to the output line.
Here's one example:
http://www.autozone.com/autozone/parts/_/N-5yc1s?itemIdentifier=223857
or
http://goo.gl/9Ld2c
I have no idea whether that's a vacuum ON or vacuum OFF control, but
it illustrates the principle. They're available in either
configuration. Cheap too, at $11.99.
Ken H.
On Tue, Jun 12, 2012 at 9:18 AM, Dennis Sexton wrote:
>
>
> Bruce,
>
> Here is one style of heater shut off valve -- takes very little room and comes sized for different hose, ie, 1/2 or 3/5 inch.
>
> http://www.amazon.com/Four-Seasons-84706-Shut-Valve/dp/B000CNJ66E
>
> Dennis
>
> rf_burns wrote on Tue, 12 June 2012 06:35
>> Well, I never did did my heater shut off valve in installed. Pager went off and my whole plans for the day changed.
>>
>> Anyway, looks like from the posting some type of bypass valving arrangement would satisfy all the requirements. I looked on-line and all I can find is industrial duty valves.. $$$$$.
>
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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] Heater core, which way does the coolant flow [message #173130 is a reply to message #173068] |
Tue, 12 June 2012 20:56 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Wow. I could use one that is electric or manual control on my John Deere. I just this afternoon had to swap hoses around to shut off my winter heat. Unfortunately diesel engines do not have a vacuum source to run that one. I still like it for use on a GMC.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Heater core, which way does the coolant flow [message #173133 is a reply to message #173130] |
Tue, 12 June 2012 21:09 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Ken,
There are cable operated versions also. Google "H-valve".
Ken H.
On Tue, Jun 12, 2012 at 9:56 PM, Ken Burton wrote:
>
>
> Wow. I could use one that is electric or manual control on my John Deere. I just this afternoon had to swap hoses around to shut off my winter heat. Unfortunately diesel engines do not have a vacuum source to run that one. I still like it for use on a GMC.
> --
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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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