Heater core flush

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Jan 22, 2011
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Why are you flushing the system? If you are using the proper coolant and only distilled water you should have no problem just doing a drain and refill when required.
He's been using stop leak tablets for some time now (9 years) and I'm sure some of that has settled in the heater core.
 
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An old vehicle showed 7 different colors of crusty leakage accumulations on the backside of the radiator.

The heater core was completely clogged. No household chemical worked.

Finally gasoline cut the grey putty which filled the heater core. The core had no leak.
 

wrcsixeight

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I was only going to try and better flush the heater core, since I am replacing the heater hoses.

The ginger root tabs have been at 1/6th the recommended dose or less, and very effective.

My last core flush was ~10 months ago, yielded a ~25 degree f improvement. White clean 5 gallon bucket catching the flush was not revealing much detritus. The increase in heat was a nice surprise, but it's not as hot as it once was.

Could easily be blend door issue too.
 

wrcsixeight

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When I was replacing those heater hoses, the one multipurpose hose, from vaccuum operated valve to core, was hard as a rock. I had to cut it off, and the metal barbed portion of the valve to which it was attached, was rusted badly. the other 5/8" barb on the valve is plastic. When i bent the hose opposite the bend it had hardened into, it took a lot of effort and then when it started to go made a crusty cracking then a snapping sound. It really deteriorated significantly in the last 10 months, as I doubt I would have returned it to service had I noticed how hard it had become on last December's flush, but it is possible.

The inside of the heater valve was about 1/4 occluded with white scale just downstream of the internal flapper. I've no recollection of ever replacing it, it could be original, in use for ~30 years. Vaccuum still moved the flapper but with vaccuum applied, which closes it, to shut off flow when in OFF or MAX AC modes, there is still a lot of flow, when I'd blow through it. I'm told the valve is not designed to completely cut off flow, to keep the AC's evap coil from frosting up, but my factory service manual indicates the flow from fan blows first through Evap coil first, then heater core, so I see no point in this valve not stopping all flow in the OFF or Max positions.

I reassembled without the valve, and blocked off the vaccuum line. My AC is non functioning/non charged anyway. The valves are cheap enough. I can return a new one easily enough, but have just not bothered, yet, and its possible I might not bother ever.

I did flush and backflush the core again. Not much in the way of black flakes came out into the cleaned white bucket. I didn't collect any before data on the heat output at vents, and its been way too hot to use the heater anyway just to test if and to what degree the heater is more effective, post flush.
I used no product, just limited hose water pressure, back and forth twice, about 9 gallons worth and let it siphon itself mostly dry before attaching the new heater hose to intake and water pump and core. The new hose is supple enough I can easily reverse the flow through the core, but unless I find the heat inadequate this winter, I doubt I'll bother.

But that pesky unused Evap core is still in the HVAC box, restricting the blower motor's flow, increasing amperage draw of the motor at higher speeds.

Perhaps I should plumb it with coolant, have a super Alpha roaster heater, as the factory service manual's diagrams make it appear that it has many times the surface area of the heater core, which several years ago was pretty dang impressive on its own. Really though I live in California at sea level, not North Dakota. I will likely cross the Rockies this winter though, nice to have a good heater.
 
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The heat control valve is there instead of a blend door. What you describe about your evaporator is not going to increase blower motor draw. The system is designed to work with the evap in place. Increasing the velocity of the air will begin to reduce the heat draw from the core's surface. You are better off to just maintain what you have and not try to redesign the system by using an evap core for heat purposes. Increase the surface area is like adding another small radiator and your engine will struggle to maintain proper running temperature.
Your obsession with your heater does make interesting reading.
 
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I do have a leak at the base of the all aluminum radiator where tubes meet bottom tank. When I drop and replace ~2 gallons, and do not add another tab, it starts weeping there again within a couple hundred miles.

It has done this each year for the last 8 years. I only added the tab once the weeping restarts, after foolishly hoping it will not, each year.
This tab is most likely why your heater core isn’t performing as it should. There is no way I would be adding any type of stop leak to a vehicle I plan on keeping.
 

wrcsixeight

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I have the ability to easily monitor amperage voltage and thus the wattage that the blower motor draws.

When i change the position of the blend door, which does actually exist, and when I change the outlet vents from floor to defrost to dash. Each change in restriction on the cage fan, changes the amp draw. When on highest speed, with 14+ volts available, as much as 3.5 amps difference, which is over 50 watts.

If you can;t see how changing restriction of the blower motor changes the amp draw, you should really not reply on such topics posturing as some authority.

Saying removing the restriction of evaporator core will not change the wattage consumed by the motor, is very much incorrect, as inconsequential as that wattage difference may be. However each 25 amps an alternator generates sucks up ~one engine HP and my blower motor can draw upto 18 amps, depending on voltage reaching the motor, and position of the blend door and outlet positions.

See I was curious, so I checked, rather than make assumptions.

Funny how actual data can smack ones assumptions upside the head, but thanks for making me regret updating this thread. Can't say the regret was unexpected though. Was hoping otherwise, but, 2020.......

this thread can die. disappear, be locked, whatever, as its been colossal waste of time and effort.
 
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Maybe should should check your blower motor. Other than changing speed, changing of the blend doors should not make that big of a difference. Small yes but not a big difference.
What is dangerous is someone who is set in their ways with a leaky radiator for eight years, handful of sealing tablets, enjoys flushing his heater core, tools, and a meter and wants to redesign their heating system but has no idea what he is doing.
 
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I remember when my uncle came over 1 time with his 1977 Chevrolet Malibu and he had no heat. Took the Heater Core off and flushed it out, put it back on, a little bit better heat. We ended up taking it off and soaking it in Prestone Super Radiator Cleaner for a few hours, then flushed it out, the heat was a tad warmer. We ended up going to Trak Auto, old timers remember that place, lets see who knows what it is called now, anyways we just put a new Heater Core on and the car got very hot.

My thought is that the Heater Core can maybe act as a filter and catch all of the junk in the Cooling System.
 
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