Heater Core Flush - what to use to agitate the junk out of the core?

Ok folks.. I have a heating problem.

I am going to do a heater core flush.. Reading the interwebs. I think I dont want to use any harsh cleaners for my 275k mile old header core. Also read that using CLR or vinegar is not recommended b/c it will corrode the aluminum which is what heater core is made from. I really dont feel like swapping the heater core if it goes bad.

I was just thinking of using plain own water in both directions to clean the heater core out. But not sure if thats the best way.. But better than nothing I guess.

What are your recommendations on cleaning the heater core? User CLR, vinegar, any other chemicals?

 

BTW these were my conditions and my troubleshooting steps I have already taken to come to figure out it may be the heater core cleaning I need.

I have no heat on drivers side but good heat on passenger side and overall lower volume of air when Temp knob is on heat (full right) vs when it is on cold (full left). i.e. when comparing volume of air when the temp selector is on cold it blows more volume of air than when on heat side.

I also was not having any delay on my HVAC controls when I start my truck up. no 30-45 sec delay or anything. (this no delay is an important clue that your servos are likely working properly - So do not open your dash to fix nothing.. save yourself some time_

So to summarize the conditions (for manual air controls) like below.
HVAC knobs set at - blower on full - left temp on full heat (full right) - direction on Face (full left) - Passenger on Sync (full left)



1. HVAC controls work on startup of Truck without any delay. i.e. HVAC system knobs are immediately functional at start up.
2. Heat air flow only coming from Passenger side vents. i.e. hot air coming from passenger vents
3. Colder air flow coming from Drivers side.
4. There is a noticeable improvement in air volume if you move the left temperature knob from heat to cold. The air volume through the vents is higher when in cold vs the hot when you move the temperature knob (the left temp knob) from full cold to full hot.
5. AC works great with more air volume compared to when on heat side.

Initially, I thought it was my servo's on the drivers that were having issue. But if you are getting those symptoms where your air controls work at startup without delay then your issue maybe heater core needs a flush.

BTW this like was very helpful - The file attached is not mine but give you great instructions on how to take the Servos out on the drivers side. and how to setup the servo gears when you need to put it back in.

 

This sounds more like a mixer issue than a heater core. If you are getting hot air in the cab that indicates that you are getting hot water through the core. I don't think there is two cores (one for driver side one for passenger), but I could be wrong.

 

Your heater core is fine. A plugged heater core is no heat at all. This is a blend door issue.

 

So, spray the blend door with CLR then?

 

Update 1 - So I put everything back together. The servo attachment on the lower drivers side. It was a pita to get it done. But do yourself a favor by putting the HVAC as I mentioned in the 2nd post. It makes putting the servo's back in a lot easier. And as others have mentioned once you setup HVAC links the servo snaps in easily.

I then inverted the heater lines coming into the heater core from the engine. And that got the heater on the drivers side working. So I suspect the heater core was either plugged up or there was air in the heater core. By swapping the lines one of these 2 happened or both. Either case the drivers side is working again.

But one thing that is not fixed the air volume.. its still noticeable lower when on heat vs when on cold. That is still not been fixed. I suspect to get this working I may have to take the whole HVAC unit out. I am not sure if I am willing to do that.

 

After I replaced my coolant I had to swap the hoses to get the air out because I had no heat on the drivers side, then swapped them back around after awhile. And it seems to be a common thing with tundras to blow more air volume on AC than on heat. My truck does the same thing. I even replaced the blower motor.

 

Having this exact same issue right now. Did you end up with a final verdict? Did the heater core flush improve air flow & temp?

 

So???? any update to this issue, I have one blowing air but just warm not hot?

 

I flushed my heater core and it got hot air although the air volume still isn’t the best. At least it’s warm!

 

Any suggestions or recommendations on a solution to flush out your heater core? I was thinking plain old water? Anybody want to suggest otherwise? Thanks.

 

I just battled this for a month. Good heat on pass side little heat on drivers side . Flushed for hourssssss with three different chemical concoctions. In the end i had to replace the heater core.

Once out, Iturned the core upside down and gobs of black flacky crud came out. Because the water has to go up 6” from the core to the hoses, the big stuff just is too heavy to be pushed uphill. Got lots of tiny pieces,but none of the big pieces. Sorry, bur it seems a dash removal is in your future. Not fun by any stretch, but doable. It is just a bad design. Core is like 12” for the dual heat and the back half , which is the driver side gets plugged with crap, but still has good flow on the front side.

 

Well sheeet! That’s sucks. Could you have worked through the glove box and center dash or do you have to take off the dash?

 

No the hvac box must come forward to clear the tubes from the firewall. Only way to get it forward is to pull the dash. The core slides out of the side of the box, but the tubes sticking through the firewall prevents it from moving much. I suppose you could cut the tubes and then use rubber hoses to splice them back together. But still not sure if there is a frame in the way, keeping it from sliding it out

I suggest you try to flush it first. Could be your blockage is different from mine. You may get lucky.