Best cleaner to flush a heater core

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Still trying to work out some kinks. I have heat but its nowhere near what it should be. Truck is a 96 GMC Sonoma 4.3. I am pretty much convinced the heater core is plugged up to some degree. What is the best thing I can use to help clean it out with?
 
I was under the impression that most heater cores today, always have flow. On older cars, the heat control shut off flow to the heater core and this caused gunk and build up. Are you sure the engine is up to temp, that the coolant is not low, and that the air flow blend door is working?
 
Eric the car guy did a youtube video on that some time ago. He used some cleaner plus compressed air to blow out the crud. I think it's a good video. Watch it if you get a chance.
 
Originally Posted By: spasm3
I was under the impression that most heater cores today, always have flow. On older cars, the heat control shut off flow to the heater core and this caused gunk and build up. Are you sure the engine is up to temp, that the coolant is not low, and that the air flow blend door is working?


This is not so much the case. There are plenty of modern cars that use a heater control valve to shut off coolant flow to the heater core and also quite a few that use a heater control valve to negate the need for a hot/cold blend door.

This heater doesn't have that. If it's partially clogged, some sort of weak acid and lots of water should be used. If that doesn't work it's time for a new one.
 
I had little heat in my '07 Grand Prix. I flushed the system of dexcool and changed the thermostat. Heater hoses were hot to the touch. Still had little heat. New coolant was clear of gunk. Starting to think I had a bad core.
Read up on how to replace a heater core and thought, there has to be another answer.
Since one heater hose already has the flush "t", I cut the other and put in another t. I hooked up the garden hose to to one heater hose and squeezed the nozzle - out came rusty colored pudding. It ran clear in a few seconds. Then I hooked up the nozzle to the other hose to back flush. Surprisingly, more gunk came out. Hooked the hoses back to normal, refilled the coolant I lost, bled the system, and you could cook a roast in the car now.
 
i disconnect both hoses from the heater core and blast through water in one direction then the other a few times that works great
 
Disconnect the hoses and run some water from a garden hose in.

If this does not work, a teaspoon or two (max 3 teaspoons or a tablespoon) or plain dishwasher detergent.
No lemon scent, not orange scent.
Not CLR or anything acidic, heater core is very thin aluminum.

Rinse out the core, reconnect...
 
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Originally Posted By: nitehawk55
Feel the heater hoses . If they are hot it's flowing , cool not .

And if there's a problem, how hard is it to change on this vehicle? If it's a relatively easy change (under 20 minutes on my F-150, hours upon hours on the old LTD), it isn't even worth playing with if it's clogged or weak.
 
Originally Posted By: Garak
Originally Posted By: nitehawk55
Feel the heater hoses . If they are hot it's flowing , cool not .

And if there's a problem, how hard is it to change on this vehicle? If it's a relatively easy change (under 20 minutes on my F-150, hours upon hours on the old LTD), it isn't even worth playing with if it's clogged or weak.


Feeling the heater hoses is a simple test just to give you an idea if the core is plugged or not . Totally plugged or almost they will be cool to warm compared to the engine hoses . If hot it should be OK but a flush is always the first method to try and clean out and it generally helps unless it's really plugged bad .Even if the hoses are hot it still is good to flush if you feel you are not getting the heat you should . Always the risk of there being a leak afterward though if lots of corrosion going on .
Make sure your engine is coming up to proper op temp or the thermostat is suspect .And of course check the operation of the heater doors or a flow valve if it has one .

How long ? no idea .
 
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Originally Posted By: Sawdusted
Eric the car guy did a youtube video on that some time ago. He used some cleaner plus compressed air to blow out the crud. I think it's a good video. Watch it if you get a chance.

+1
 
Originally Posted By: nitehawk55
Feeling the heater hoses is a simple test just to give you an idea if the core is plugged or not.

Exactly. If there's a question, I lean towards a change, since the corrosion can always be a problem. But, on some vehicles, it's a ridiculous job and I wouldn't blame someone for trying flushing first.
 
I watched EricTheCarGuy heater core flush and it looked pretty good. The only thing that concerned me was the use of compressed shop air for purging the heater core. My Chrysler manual is very specific about not over-pressuring the radiator, something like 20 PSI max. I'd go very gentle with the compressed air, lest you pop the heater core.
 
Originally Posted By: Rick in PA
I watched EricTheCarGuy heater core flush and it looked pretty good. The only thing that concerned me was the use of compressed shop air for purging the heater core. My Chrysler manual is very specific about not over-pressuring the radiator, something like 20 PSI max. I'd go very gentle with the compressed air, lest you pop the heater core.


I would be concerned about the air pressure causing damage in the form of a leak , then you really have a problem .

Generally the water pressure from your garden hose will work and it's not just the pressure it's the volume of water that's being flushed through it and doing it a few times in opposite directions .
I did this a lot when I was in the trade and it amazed me how much crud came out and then you flushed the other way and more crud ! Usually made quite a difference in how the heater performed
smile.gif


Of course that was some years back when you could actually get at the hoses !
 
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Originally Posted By: crazyoildude
i disconnect both hoses from the heater core and blast through water in one direction then the other a few times that works great


This.

This method is the simplest and fastest way and is very effective. Whenever I have a plugged core, this is what I do and it has yet to fail me.
 
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