Externally Cleaning Heater Core?

[sirhcx]

So it's that lovely time of year again where its cold enough in the morning that having heat would be wonderful but the best my 2001 SR5 can do is slightly warm.

The heater control valve inlet and outlet hoses are both hot as well as the heater core return hose. So that gives me some hope that it's not an internal clog but I'm still not really getting much heat well after the thermostat has opened. I read in another forum that "If the return hose IS nice and hot, chances are the heater core is clogged with dust, dirt, leaves, whatever, externally. Take the casing off of it, and blow air through it in the reverse direction than the blower does".

The problem is that I have no idea how to access the heater core without tearing the whole dash apart. I was going to clean out the blower motor soon and figure killing two birds with one stone if both jobs are accessible at the same time. I would appreciate any help in this manner so I can keep my ol' Betsy limping along a few more years as my daily driver.

 

[alumarine]

I can't help with accessing the heater core but 99% of the time a lack of heat is not due to it being full of dirt externally.

When you say the heater valve is "hot" what's the temperature?
It should be at least 160-170 F.

 

[sirhcx]

I can't help with accessing the heater core but 99% of the time a lack of heat is not due to it being full of dirt externally.

When you say the heater valve is "hot" what's the temperature?
It should be at least 160-170 F.

I don't have an exact measurement but all 3 hoses are definitely too hot to touch for more than 5-7 seconds. The dash shows the engine temp is a little over the middle position as well.

 

[alumarine]

I don't have an exact measurement but all 3 hoses are definitely too hot to touch for more than 5-7 seconds. The dash shows the engine temp is a little over the middle position as well.

That could mean 110-120 degrees or it might be ok.
Without a temp gun reading you won't know.

 

[phattyduck]

How's the airflow when you are set to full hot? Does the actuator fully turn the valve in the engine bay? (the '01/'02 use an actuator even on the "manual" AC, I believe).

You can pretty simply pull the HVAC blower and the blower resistor and see/access at least some of the evap core, but the heater is 'behind' that, so not so easy to access. You can do a vacuum cleaning then maybe one of the 'foaming' cleaners - Toyota even has a kit for that.

-Charlie

 

[sirhcx]

How's the airflow when you are set to full hot? Does the actuator fully turn the valve in the engine bay? (the '01/'02 use an actuator even on the "manual" AC, I believe).

You can pretty simply pull the HVAC blower and the blower resistor and see/access at least some of the evap core, but the heater is 'behind' that, so not so easy to access. You can do a vacuum cleaning then maybe one of the 'foaming' cleaners - Toyota even has a kit for that.

-Charlie

Airflow seems fine all things considered, AC blows as it should as well. Actuator works as it should but I unhooked it and turned the heater control value manually to allow the highest rate of flow. The heater core return felt as warm as the heater control valve hoses. I wonder if I just have a blockage and there simply isnt enough thermal mass for the heater to properly work. Guess I need to do a reverse flush this weekend.

 

[phattyduck]

Do you hear the heater blend door operating when you go from cold to hot? If no air is going over the heater core (bypassed by the blend door) then you wouldn't get heat despite having coolant flow through the core.

-Charlie

 

[sirhcx]

Do you hear the heater blend door operating when you go from cold to hot? If no air is going over the heater core (bypassed by the blend door) then you wouldn't get heat despite having coolant flow through the core.

-Charlie

Not my video but you're talking about this part right? The "clicking culprit" that tends to also fail over time and moves the heater control valve cable back and forth? I replaced it earlier this spring and now no more clicking as it freely moves the cable so I have proper AC for the first time in years. Is that little arm supposed to move more than just the cable though? Maybe I missed clicking stuff back together that changes the airflow from the AC to the heater core?

https://www.youtube.com/watch?v=xxUJam4Km6k

 

[sirhcx]

Too dark to get a picture but I did end up pulling the "blend motor actuator" and started to work the area by hand while the blower motor was off. There is some significant resistance but it started to ease up a little. I was able to see what looks like a long, rusty bolt that is more on the drivers side which appears to be attached to all the linkages. Unfortunately I couldnt really see if it was moving or even if was supposed to. I still get a little heat when "maxing out" the arm to the full heat mode but nowhere near what it should be outputting. All the linkages seem to be under and behind the radio, so maybe I'll look in that direction. Im also contemplating if my heater core is clogged in a way that plenty of hot coolant goes out the return but it just cant get the whole core hot. I did notice that turning the on the seems to make the tick up an extra 200-300 RPM intermittently when idling.

 

[Atimm693]

The evaporator is in front of the heater core, typically it will get plugged with crap first as it's the first line of defense, and is usually damp when the A/C is running.

The way the heater box is laid out, air always passes through the evaporator, but on full cold it is diverted around the heater core. So it would be very unlikely for the heater core alone to dirty.

 

[sirhcx]

The evaporator is in front of the heater core, typically it will get plugged with crap first as it's the first line of defense, and is usually damp when the A/C is running.

The way the heater box is laid out, air always passes through the evaporator, but on full cold it is diverted around the heater core. So it would be very unlikely for the heater core alone to dirty.

Could that lead to condensation not making it's way out the drip tube that leads outside the firewall? On incredibly humid days, the evaporator would "sweat" clear water onto the passenger floor. Can I clean anything up without removing essentially the entire dash?

 

[Atimm693]

Could that lead to condensation not making it's way out the drip tube that leads outside the firewall? On incredibly humid days, the evaporator would "sweat" clear water onto the passenger floor. Can I clean anything up without removing essentially the entire dash?

Not likely related, that drain hose just empties the bottom of the HVAC housing. Usually forcing a stiff wire up through them, or a little toot of compressed air will clear the drain.

You can access quite a bit of the core and the HVAC box through the blower motor hole, sounds like it may be worthwhile for you to take it out and give it a good cleaning.

 

[phattyduck]

Could that lead to condensation not making it's way out the drip tube that leads outside the firewall? On incredibly humid days, the evaporator would "sweat" clear water onto the passenger floor. Can I clean anything up without removing essentially the entire dash?

A long zip tie or a length of weed eater 'string' up from outside will get at least some clearance through the drain hole. For the inside, just see what you can see there through the blower and blower resistor hole and clean up what you can as a first step.

-Charlie

 

[wcjeep]

I have bench cleaned a heater core. Old Chevy heater core had long ago ceased production.

Recommend an infrared thermometer heat gun. $20 on Amazon. Eliminate some guess work. Try not to unload the parts canon.

 

[Romeo1]

Your heater core is clogged. It's very common on 3rd gen's due to the system arrangement of the heater shutoff valve sitting so high and radiator issues. Then the added problem of people can't seem to maintain cars and degas bottles get ran dry causing corrosion and junk in the system.

Use this OTC flush gun or one like it. I got mine on Amazon, link is below. Blast it internally forwards and backwards until clean. If the radiator isn't perfect change it. Maybe just change it anyway. Flush it he engine while your doing it too. Bottom up and top down. I did my passenger rear heater core also. Well worth doing it all. System is perfect, and hot as can be. One of those cars that get hit in about a minute which is nice in the winter.

https://a.co/d/5GnwWi3

https://a.co/d/5GnwWi3

Mine was clogged solid. My heater valve had lots of decay on the hose nipples also.Radiator had all kinds of epoxy from shoddy repairs before my ownership.

Clean it all up and keep the degas bottle full, you won't have issues again.