Another 'no heat' thread (SOLVED!!)

This problem has been solved. It may be instructive for some to read through, but the problem turned out to be simple and much effort was put into avoiding the solution....it is an excellent example of the principle of parsimony...simplest solutions...it was a clogged hose all along...

I've read a bunch of the 'no heat' threads....the one piece of info I am missing is: what temperatures should I expect the heater core hoses to reach?

Upper radiator hose gets to about 140.

Heater core hoses both around 110....but no hot air coming out of the cabin vents.

we can hear the internal air flow damper move.
we have airflow from the vents.
we can see the heater control valve on the firewall move

have not yet flushed the heater core.
no radiator fluid smell in cabin.
radiator flushed and properly burped.

 

And you're sure the servo motor is functioning? If you're getting 110° on both the inlet and outlet hose from the heater core, I doubt it's clogged.

 

Thanks for your response.

We can clearly hear what sounds like a flap (blend door) moving in the cockpit when we switch from cool to heat....is the blend door controlled by the servo motor?....or does the servo motor control something else?

 

97 should be a cable for the temperature control; no motor. Not much to go wrong in that department. If there is, you would typically feel it in the lever.

 

If the coolant passing through the heater core with the water control valve open is only about 110 degrees fahrenheit, then the engine either isn't fully warmed up yet, or you have a restriction/air bubble somewhere. The coolant flowing through the inlet should be closer to 160-200 degrees fahrenheit, and then slightly cooler after it passes through the heater core.

Some things it could be:
A. Low on coolant
B. An air pocket in your coolant somewhere
C. A clogged coolant passage/hose
D. A stuck open thermostat (rare, but it does happen)

A and/or B are probably the most likely culprits

 

i just ran into this thread
i had no idea....
per my Q 'relatively' same plug bolt location 2.4L/2.7L/3.4L
and
crap ton of coolant in block(much more than i expected per pix)

https://www.tacomaworld.com/threads...the-block-drain-to-3-4l.818760/#post-29382407

that would confirm choice 'B' that fantastic posted.

 

I recently had the same problem in my 98 tacoma. i was having mediocre heat. The temp control is rod actuated. Look under the dash on the passenger side and make sure the rod is fully seated in the blend door clasp. I took a picture of the culprit in my thread about the same issue.
https://www.tacomaworld.com/threads/anemic-heat-solved.817111/#post-29309062

 

At 140F on the radiator hose it sounds like your thermostat is stuck open. What does the temp gauge look like? Heater vent temp should be around 130F

 

continued struggles with the issue...Flushed heater core this morning....good flow through the core.
Topped up coolant, ran it to get it up to temp...Thermostat opens normally and we get fluid flow.
Drove it around the block. Upper hose temp is 160, Heater inlet hose 125, outlet hose about the same.
Still no warm air from vents.

re-examining the blend door....it appears to actuate normally.
In the image I cycle it from cold to hot and back to cold (unless, like I always am....I got it 180 out)
I'm kinda stumped...

 

tstat is stuck open, coolant temp should be 180-190 deg f after warming up

 

Hard to tell what's all going on from that angle, but these are the two things that should be happening when you move your temperature slider:



That being said, your coolant temperature at the heater core lines should be hotter than 125 still after warmed up.

 

Also, the FSM states that the thermostat for the 2RZ/3RZ should open in the range of 176-183°F. That should give an idea of what the coolant temperature should be staying near.

 

It's a year later and the no heat issue is rearing it's frozen head once again. Here is where we are: In the past year we have replaced the radiator (old one had a hole) and thermostat and recently replaced the heater core. There is still no heat. We are convinced that there is no air bubble....squeezing all hoses (both radiator and at the heater core) results in fluid backflow, but no air bubbles. We are focused now on the actual flow of fluid to and from the heater core. Today in Alabama it is 55 degrees, we ran the Taco up to normal operating temp, can see fluid circulation at the radiator, thermostat temp is over 180, so it is open....but the inlet hose to the heater core is at 78 degrees and outlet about the same. So the question is why are not getting hot coolant flow through the heater core? As always your words of wisdom and encouragement are welcome.

 

Sorry bro

this is my take
From your vid
This arm appears not to move the “warm to cool” rod as much throw as needed
Also, after blowing vid up, said arm’s hole at the end looks “ a bit wollared out”

 

Easy test is to push that affect arm in correct warm position, secure arm somehow, get up to operating temperature and see if there is a change

 

glad you are NOT in a place that is ~10 degrees such as in Michigan a dozen days back
OMG the cold and wind was real it chapped my hands

 

So we finally solved it....we were correct in thinking that we were not getting flow through the heater core....turns out that the stop leak the original owner had added to address a radiator leak had completely clogged the inlet tube to the heater core....we flushed the core because this was a concern, then ultimately replaced the heater core....but we never checked the inlet hose to the heater core....plugged up like a big man that ate a cheese ball all on his own....thanks to all that spoke up here....great community.

 

Cool beans, fixed. Occam's razor I'm definitely guilty of not practicing it. Merry Christmas stay warm my friend.

 

Excellent!!!

stop leak FTL…….again