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Thread: Heater flow issue

  1. #1
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    Heater flow issue

    I have an issue with no heat in my van.
    - 1984 Hiace YH51
    - 3Y motor
    - Don't have any overheating issues and gauge sits where it always has for the past 20 plus years.
    - Have replaced the heater control tap and verified that it is open
    - Have replaced the thermostat and all hoses recently
    - New radiator 12 months ago as the last one sprung a leak.
    - System has been flushed a couple of times and is clean
    - Heater core has been flushed separately in both directions and seems to have good flow
    - Have removed the heater hoses from the core and started the engine but nothing pumps through the hoses.
    - If I connect a hose to the disconnected heater hoses I can push water through the system in both directions which suggests that it is not a blockage and that the thermostat is open
    - Have idled the motor at length to get it hot and increased revs without any obvious hose collapse

    My initial thoughts were that I had a blocked core and not wanting to pull half of the car apart to fix it I flushed it out but no cigar. I haven't had any overheating issues so assume that the water pump is working correctly, just don;t get any flow through the heater hoses.

    What circulates water through the heater hoses? Is it the general flow of water through the system? If so then why does water not flow when it flows freely with hoses disconnected and connected to a garden hose? Does the water pump perhaps have a separate function for circulating water through the heater and this part is defective even though the general circulation seems to be ok?

    Would appreciate any thoughts as it is a bit chilly driving to work in the morning and having to use cold air for demisting the windscreen.

    Tools

  2. #2
    Administrator llamavan's Avatar
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    Re: Heater flow issue

    You can find documentation on the heater hose routing for US Vans HERE.

    Water (and/or coolant) is circulated through the heater hoses entirely with the water pump, thus moving while the engine is actually running ... IF the valve in the heater hose is in the open position. For the symptoms you describe, I'd track down that valve first and investigate whether it's in the closed or open position. For a US Van, that shut-off valve is showing in the fourth photo in the linked article above. The valve itself could be the issue, but more often the control cables are the problem (stuck, broken, or detached), and you will need to manually change the position at the valve until the control cable issue is resolved.

    A thread about the heater valve is HERE.

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

  3. #3
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    Re: Heater flow issue

    Thanks Gwen. I have already confirmed that the valve is open, so it is purely an issue of no water flow.

    Tools
    Last edited by tools; 07-04-2022 at 03:26 AM.

  4. #4
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    Re: Heater flow issue

    Theres also a couple of threads regarding bleeding the cooling system, it can be difficult to get all the air out of the core, due to its location/orientation.

  5. #5
    Van Fan Harbilly's Avatar
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    Re: Heater flow issue

    gwen’s got it. The spider at the dash fails. We’ve been sliding under the nose to manually adjust the heater valve on our cargo van for 16 years. it used to be annoying but now we have children big enough to do it for us at $1 a pop. I realize your valve is open and this doesn’t help you but it’s the most common thing to know and useful advice in most situations.
    you might have an air lock. Water pump could be weak - that’s an easy enough swap out. How about a gunked up and blocked hose from rust and flushing? I read you pushed water through things but did you get all the way back to block? We leave the valves partially open on the heaters all the time just to keep things flowing and prevent jam ups.

    Quote Originally Posted by llamavan View Post
    You can find documentation on the heater hose routing for US Vans HERE.

    Water (and/or coolant) is circulated through the heater hoses entirely with the water pump, thus moving while the engine is actually running ... IF the valve in the heater hose is in the open position. For the symptoms you describe, I'd track down that valve first and investigate whether it's in the closed or open position. For a US Van, that shut-off valve is showing in the fourth photo in the linked article above. The valve itself could be the issue, but more often the control cables are the problem (stuck, broken, or detached), and you will need to manually change the position at the valve until the control cable issue is resolved.

    A thread about the heater valve is HERE.

    Gwen
    Last edited by Harbilly; 07-09-2022 at 10:29 AM.
    Arghhh. Har Har Har. It's a pirate's life for me!

    86 2wd cargo
    89 4wd (now a crumpled mound of parts in the front yard)
    97 4Runner Limited

  6. #6
    Van Fan Harbilly's Avatar
    My Van(s):
    Vanessa the 86 2wd cargo and Rusty the Troubled 89 4WD. Update: Rusty is dead. A trailer dragged him over a cliff. He is crumpled and in my front field and donating parts to keep Vanessa on the road.
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    Re: Heater flow issue

    after doing anything to the cooling/heating system we start up in the am with the rad cap off and idle for a bit while bubbles find their way to the cap neck and go away. Heater valve wide open. Rear heater too. 2-6 weeks has always worked for us in terms of getting the air out. FWIW. Ymmv.

    Quote Originally Posted by Burntboot View Post
    Theres also a couple of threads regarding bleeding the cooling system, it can be difficult to get all the air out of the core, due to its location/orientation.
    Arghhh. Har Har Har. It's a pirate's life for me!

    86 2wd cargo
    89 4wd (now a crumpled mound of parts in the front yard)
    97 4Runner Limited

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