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Old 10-04-2011, 10:02 AM   #1
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Join Date: Sep 2011
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Heater core not getting coolant

Took my 2001 Itasca Horizon in for a Coolant Flush and Fill and also check why my newly replaced heater core is not getting coolant flow. The local FL chassis guys completed the F&F but could not find out why the coolant was not getting to the heater core. They said the hose first goes to the water tank then from there to the heater core. They wanted to pull the water heater to see if any hoses were crimped…but with the $$$$ clock ticking I told hold off and I would pick the unit up this afternoon. Any thoughts on were I might look for the problem? Does anyone know if that's the flow, Engine – Water tank – Heater core… They did say the on/off valves seem to be working…. Hoping it's just a hose crimped somewhere. As always, thanks for the help.
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Old 10-04-2011, 10:07 AM   #2
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How come no one pulled the hose from the cores input and checked to see if water was flowing???? Then from the valve, then the tank, and so on?
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Old 10-04-2011, 10:20 AM   #3
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The heater core may be air bound. You may have to loosen one of the heater hoses and burp the core.
Kathy & George Zimm & 1 Sheltie, Lancelot
Mickleton, NJ
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Old 10-04-2011, 11:01 AM   #4
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Turn your heater on full blast and open the de-gas bottle top to let any trapped air out. Let it run for 20 minutes or more. If that doesn't work then feel the hose coming into the heater valve it should be hot. Then feel the hose coming out of the heater valve into the heater if it's not hot you need a new valve. Go to lowes and buy a 3/4 brass lever ball joint valve and 2 - 5/8 inch barb ends for $22 and replace your big $$ valve with it. Good luck.
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Old 10-04-2011, 11:05 AM   #5
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According to the parts diagrams (2001 Catalog Menu), all 3 versions of a 2001 Horizon use the same setup for the automotive heater circuit. First thing to do is heat up the engine then go see if the 5/8" heater hoses running up the passenger side frame rail are getting hot. The drawing indicates there is a vacuum controlled valve at the heater core that has to be open for water to pass through the heater core. Additionally, there a air mixing deflectors in the heater unit that have to be in the correct position for air to flow over the heater core.

I looked at pdf pages 168 and 172 of which is for the IKP36CD model. The other 2 versions (available at the link above) have simular drawings under the Heater/AC section, sub heading automotive. For following the hose path, on page 168, you are interested in key #'s 1, 2, & 5. Same on the other version drawings. If water is flowing, the hoses will be hot when engine is warmed up.

Dave in Virginia
1978 Winnebago Chieftain
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Old 10-04-2011, 04:36 PM   #6
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Well back at home. All hoses to the heater core were cold. I took off the front bottom hose connected to the heater core and fluid gushed out flowing downward from the top hose through the valve. Quickly put that back on. Not a mecahnic so bare with me. The bottom hoses come from the rear, I'm assuming one to deliver coolant and one to take back. Both hoses are connected to a black plastic "valve". Then there are two hoses connected to the top of the valve, thinking those go into the heater core.
Maybe its the valve....calling my mobile RV guy tomorrow to come out and take a look. Like I said the FL chassis guys thought it might be the blocked coming out of the water heater but with the fluid in the system up front, not sure that's it. Thanks everyone for the advice.
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Old 10-04-2011, 06:28 PM   #7
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When I had my coolant changed in my 03 Journey DL, the folks doing it forgot to open the valve that lets the coolant go to the front unit. Once this was opened everything was ok.
What do you do when you just can't do what you do when you do what you do?

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Old 10-04-2011, 08:25 PM   #8
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On my 2006 Journey with Caterpillar engine there is a 3/4 inch coolant hose with a ball valve located on the left rear side of the transmission just aft of the rear wheels. I think this valve is located there to be used to shut off the flow of coolant to the heater core up at the front of the coach in case of a leaking core. Here is a picture of my valve. It needs to be in the on position for the heater to work.


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Old 10-04-2011, 10:14 PM   #9
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We had a coolant flow problem to the heater core after I had worked on the water heater. When I reinstalled the water heater I accidently kinked the line and stopped the flow to the heater.

It was my fault and had me scratching my head for awhile until I talked to Freightliner about coolant flow direction. Once I got the kink out, everything worked normally, problem solved.
Denny, Connie & Shadow (former barn cat made good)
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Old 10-06-2011, 07:48 PM   #10
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My replacement heater core came with rubber plugs in the inlet and outlet tubes that looked like "washers". Pull the hoses off the heater inlet and outlet and make sure there is only metal tubing and not any black rubber plugs still in the tubing. Poke a wire into the tubes to make sure there is not something obstructing them.
Travlin Ken
2002 Itasca Horizon 36LD
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Old 10-11-2011, 03:55 AM   #11
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Thanks everyone,,,esp. Martind4 - turned out to be the hoses for the water heater. Whoever worked on it last time just shoved the unit back in kinking the hoses in several places. Removed the heater and replaced the hoses...problem fixed.
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Old 10-11-2011, 08:30 AM   #12
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We had that problem.. It was a vacumn activated H valve Replaced that And everyone was happy.
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Old 10-11-2011, 10:36 AM   #13
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zoocrackers....thank you so much for the feedback on solving the problem. And Martind4 also for sharing his experience!

Way too many times, folks just don't let us know what fixed their particular concern...and the rest of us don't learn very much from the experience. The beauty of this forum is to help one another, if possible, and to prevent us from constantly "remaking" the wheel, so to speak, when these technical gremlins crop up. Thanks for the info!!
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