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#3176971 - 11/03/13 09:15 AM Best cleaner to flush a heater core
nomochevys Offline


Registered: 11/26/05
Posts: 394
Loc: Ky
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?

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#3176984 - 11/03/13 09:29 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
Warstud Online   content


Registered: 09/02/05
Posts: 5186
Loc: MIchigan
What have you done so far to get more heat?

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#3176996 - 11/03/13 09:35 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
spasm3 Online   content


Registered: 05/30/10
Posts: 8417
Loc: North Carolina
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?
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#3177005 - 11/03/13 09:45 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
JHZR2 Offline



Registered: 12/14/02
Posts: 41403
Loc: New Jersey
Citric acid flush and degreasing per the MB FSMs.

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#3177009 - 11/03/13 09:47 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
michaelluscher Offline


Registered: 10/07/12
Posts: 2379
Loc: Staten Island, NY
If you've fully established that the heater core is plugged.
CLR would be quite good, a couple vinegar rinses after that would be good.
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#3177016 - 11/03/13 09:54 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
Sawdusted Offline


Registered: 12/25/12
Posts: 426
Loc: The Tropical Fine City
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.
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#3177021 - 11/03/13 09:56 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
nitehawk55 Offline


Registered: 04/01/10
Posts: 1084
Loc: Ontario , Canada
Feel the heater hoses . If they are hot it's flowing , cool not .
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#3177032 - 11/03/13 10:05 AM Re: Best cleaner to flush a heater core [Re: spasm3]
yonyon Offline


Registered: 03/06/12
Posts: 3492
Loc: NJ, USA
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.

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#3177033 - 11/03/13 10:06 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
Chris142 Offline


Registered: 06/05/03
Posts: 16507
Loc: Deplorable in apple valley, ca
Air and water if its plugged up
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#3177070 - 11/03/13 10:27 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
PhillyJoe Offline


Registered: 03/19/09
Posts: 655
Loc: PA
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.

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#3177081 - 11/03/13 10:38 AM Re: Best cleaner to flush a heater core [Re: PhillyJoe]
crazyoildude Offline


Registered: 07/23/08
Posts: 9808
Loc: New Jersey
i disconnect both hoses from the heater core and blast through water in one direction then the other a few times that works great
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#3177102 - 11/03/13 11:04 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
mattwithcats Offline


Registered: 06/13/13
Posts: 1613
Loc: Virginia
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...


Edited by mattwithcats (11/03/13 11:05 AM)
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#3177119 - 11/03/13 11:22 AM Re: Best cleaner to flush a heater core [Re: nomochevys]
nitehawk55 Offline


Registered: 04/01/10
Posts: 1084
Loc: Ontario , Canada
Important to flush core in both directions .
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#3177123 - 11/03/13 11:27 AM Re: Best cleaner to flush a heater core [Re: nitehawk55]
Garak Offline


Registered: 12/05/09
Posts: 24051
Loc: Regina, Saskatchewan, Canada
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.
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#3177157 - 11/03/13 12:18 PM Re: Best cleaner to flush a heater core [Re: Garak]
nitehawk55 Offline


Registered: 04/01/10
Posts: 1084
Loc: Ontario , Canada
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 .


Edited by nitehawk55 (11/03/13 12:21 PM)
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