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Heater (and A/C) problem diagnosis

 
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  #21 (permalink)  
Old 03 Nov 2019, 12:51 pm
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Default Re: Heater (and A/C) problem diagnosis

Reviving (hopefully) this thread. I ran out of winter and stopped worrying about it before. But it's alreayd cold and I thought I'd take another crack.

Previously on The Heater Chronicles

1. Flushed heater core BOTH WAYS.
2. Changed thermostat and radiator cap.
3. Flushed and filled system on an incline and worked to remove any possible air pockets.
4. Examined cable from the controls, it works fine.

Observances:
Heater core hoses don't get as hot as I would have thought they should. No discernible difference between upper and lower.

QUESTION: Could a water pump work well enough to circulate coolant through the engine, while NOT working well enough to push coolant through the heater core?

QUESTION 2: Is there a way to confirm that the blend door itself is actually working without taking it all the way out?
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Old 04 Nov 2019, 09:32 am
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Default Re: Heater (and A/C) problem diagnosis

I'm pretty sure you have a blocked heater core.
Try this:
  1. Disconnect both hoses at the metal fittings on the engine side of the hoses, not the firewall side.
  2. Get a garden hose with a nozzle that fits the rubber heater hose
  3. Turn the water on at a low volume and loosely fit the garden hose nozzle to one of the heater core hoses. I say loosely so you don't put 120 psi against the heater core if it is truly blocked
  4. Obseve the water coming out the other hose (or lack of water)

You don't even need a garden hose if you can get a funnel and can pour water in through one of the hoses.

There should be as much water coming out of the other hose as you pour in. If not, first check the heater core hoses. If they are clear, you have a blocked heater core.

By all means don't force water through the heater core with more than 14 psi, otherwise it can burst or split and you will have to bypass it until you replace it or have a constant stream of coolant flowing into your dash and onto the floor of your car.

Replacing the heater core is not impossible, just a very long process of removing the entire dashboard and all associated parts (or $1000 labor) to replace a little sub $100 part.

Good luck.
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  #23 (permalink)  
Old 04 Nov 2019, 10:16 am
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Default Re: Heater (and A/C) problem diagnosis

Thank you for the response but I already flushed the heater core reverse and then forward exactly as you described. While it did flush out some small particulates, the water flowed through fine.

I guess there may be a partial clog, but the temp of the air never even gets a little warm. I may try to soak using a radiator flush or clr however, I'm about 90% sure this isn't the issue. Unless there's a reason that uninterrupted flow through the heater core wouldn't rule that out?
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Old 04 Nov 2019, 11:52 am
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Default Re: Heater (and A/C) problem diagnosis

OK, next step. Put a piece of clear tubing from the top hose of the engine outlet to the bottom hose of the engine inlet. You're now bypassing the heater core with the coolant going through the clear tubing. Make sure the tubing is rated at least 200F and use hose clamps to ensure the hose does not pop off under the pressure of the water pump.

If you say that the hoses both stay cool when the engine is warmed up, then it seems clear that there is no hot coolant flowing through them and a blockage somewhere. You've eliminated blockage in the heater core and hoses, next work backwards.

When I was diagnosing my overheat problem, I used a sump pump to pump water from the bottom hose and back out the top hose with the heater core bypassed and saw good flow. Then I reversed it and still saw good flow. You can see the clear tube bypassing the heater core.



The PT has a pretty good trap at the bottom of the engine which accumulates rust particles and other debris so it's a good idea to bypass the radiator and heater core to keep the crud from circulating and getting caught in there

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Old 06 Nov 2019, 04:21 pm
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Default Re: Heater (and A/C) problem diagnosis

I have a couple of questions.

I don't have a sump pump, will a hose not work for this? Are you checking through the whole engine this way? How do you bypass the thermostat or am I not understanding something?

Also, we're not having any overheating issues so how will this find problems with the heater?

Sorry, just want to make sure I follow what we're trying to eliminate.
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  #26 (permalink)  
Old 06 Nov 2019, 04:57 pm
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Default Re: Heater (and A/C) problem diagnosis



You can see there are only 2 hoses to the heater, in and out. If you disconnect the hoses to the heater core, you can run water into one hose, through the engine and water should come out of the other hose. Again, if you use a garden hose, don't make a tight seal or you might expose your cooling system to 120 psi or whatever your home water supply pressure is.

With the thermostat closed, the water will not circulate through the radiator. You can use a water hose and you don't need a sump pump. I used a sump pump to not waste water and I was attempting to clear a blockage in the engine. There were several ports in the headgasket that were clogged and no flushing was able to clear them. I eventually had to remove the head, clear the ports and the overheating was completely fixed.
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a/c problems, blend door, heater, heater core, thermostat


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