Other half's car - has the 3.0 - H6 engine.. about 210k on the clock (give or take a couple thou)

no signs of coolant leaks anywhere, rad full, overflow at appropriate level.. temp gauge reads normal, but NO heat (electronic climate controls)

upper rad hoses are hot, bottom hose is cold...

Assuming thermostat stuck in closed position, or should we be looking at water pump as well?

edit to add: heat was working fine on his way home yesterday evening, but not working this morning - and subzero ambient temps this morning..

Edited December 29, 20205 yr by heartless

Feel the heater hoses.

Hot upper hoses and cold bottom means the thermostat is almost certainly working (at the very least, there isn't any flow through the radiator, but if the coolant level was low or had bigger circulation problems, the engine would likely be hot and the upper hose wouldn't).

If one heater hose is hot, there isn't flow there, likely core is plugged. If they're both hot, then it's an issue with the control (air is being diverted around the core, it's not calling for heat). There's a diagnostic procedure for the auto temp control in the FSM, I haven't had to mess with it on our '00-'04s, and I avoid the 05+

 

ANY issue related to cooling system should immediately trigger a look in the radiator itself. do not rely on the overflow res. level (though important not to be empty) as a reliable guide to coolant volume. with gauge normal and no heat -- maybe low coolant?

 

heratless, I bet you do but, make sure the thermostat is OEM style.

 

is heat directed out the defroster?

Edited December 29, 20205 yr by 1 Lucky Texan

As Numbchux said, if both heater hoses get hot then the problem lies with the door actuators in the heater box or the unit that controls them. Probably the Air Mix door actuator. I've replaced a few of them on different vehicles. Sometimes called blend door actuator.

In sub-zero weather the lower radiator hose might get a little warm, but will not get hot unless you have cardboard in front of the radiator.

Edited December 29, 20205 yr by Rampage

7 hours ago, Numbchux said:

Feel the heater hoses.

Hot upper hoses and cold bottom means the thermostat is almost certainly working (at the very least, there isn't any flow through the radiator, but if the coolant level was low or had bigger circulation problems, the engine would likely be hot and the upper hose wouldn't).

If one heater hose is hot, there isn't flow there, likely core is plugged. If they're both hot, then it's an issue with the control (air is being diverted around the core, it's not calling for heat). There's a diagnostic procedure for the auto temp control in the FSM, I haven't had to mess with it on our '00-'04s, and I avoid the 05+

@Numbchux and @Rampage - i did mention the hoses....

9 hours ago, heartless said:

upper rad hoses are hot, bottom hose is cold...

 

4 hours ago, Rampage said:

As Numbchux said, if both heater hoses get hot then the problem lies with the door actuators in the heater box or the unit that controls them. Probably the Air Mix door actuator. I've replaced a few of them on different vehicles. Sometimes called blend door actuator.

In sub-zero weather the lower radiator hose might get a little warm, but will not get hot unless you have cardboard in front of the radiator.

 

I personally did not go out and feel the hoses this morning.. He did.. said the bottom hose was ICE cold - car had been running for at least 10 minutes.. maybe 15.. and he was getting NO heat at all - fan WAS blowing, however.. blowing cold air. Climate control was set to 80 he said

 

9 hours ago, heartless said:

no signs of coolant leaks anywhere, rad full, overflow at appropriate level.. temp gauge reads normal, but NO heat

Again, I am going by what the other half said.. I did not go and check personally, but He is pretty well versed himself, so I think he knows the difference between full, and not full..

 

 

 

 

We were asking about the heater core hoses that go through the firewall to the heater core.

One or both, cold, warm or hot after a few minutes of idling?

With the temp gauge at normal, both of those hoses should be hot.

When you said bottom hose, I think of radiator hoses.

oof.. sorry.. my mistake/misunderstanding.. that I am not sure about.. will have to check tomorrow - after the snow quits, and after verifying the radiator is full when cold

 

No problem, I do the same thing sometimes, skip a word then have to read it again.

We need to know if coolant is flowing through those two hoses and the heater core.

gotcha! like i said. will check into that tomorrow when the snow lets up.. snowing and blowing at the moment and rather chilly out

 

ok, update as of less than 15 minutes ago...

topped up the radiator - was very slightly low, but not low enough it should have caused a no heat situation... overflow also got topped up just because

I turned everything off when I started the car & let it come up to operating temp.. temp gauge rock solid dead in the middle of the sweep.

heater temp was still set to 80 on Drivers side, 70 on pass... turned it on, and lo & behold, we have heat, and plenty of it...

So.. thinking this is NOT heater core, t-stat or water pump related... electronics perhaps? I dunno, not familiar enough with the climate control system

What say you guys?

1 hour ago, heartless said:

thinking this is NOT heater core, t-stat or water pump related... electronics perhaps?

It is nice that it is working.......but...now what do we look at?

Electronics is a possibility and could be random. Electronic circuits work best when cold, but connectors and solder joints do not.

Letting the engine warm up before trying the heater could be the secret. Hot coolant flowing through the heater core would warm up the box it is in and help the (electric) door actuators to work.

yeah.. not sure what to do, where to look next on this..

He is going to give it a try tomorrow morning, so we shall see

 

Start it up earlier in the morning.

gotta tell him that, LOL

but yeah, I let it run for a good 15 mins before testing the heat

 

apparently the heat worked fine this morning, he took his car to work.. but, not quite as cold either.

I suggested that he not turn the fan on full blast right away, and make sure the fresh air intake was set to recirculate when it is that cold, lol

so... this seems to be resolved for the time being..

Probably best to be familiar with the diagnostic mode of the Auto A/C, so some tests can be run when it's acting up.

will check into that. thanks. =)

 

UPDATE: Jan 23, 2021 - the saga continues

He has been driving the car with no further issues until just the other day (Wednesday) - started the car to let it warm up before heading to work... hmmm, no heat again.. He decided to try going with it anyway.. started down the road and noticed within a couple miles that the temp gauge was climbing.. when he went to turn around he also noticed steam coming from under the hood.. brought it home & took my car to work.

FF to today - popped the hood & found the little hose for the overflow had come loose from the radiator, radiator level was low. There was also coolant on top of the engine on the drivers side - we are assuming the coolant on top came from the overflow outlet when the little hose came off..

Sopped up the mess on top of the motor, topped up the radiator, and suddenly the heat works again.. No obvious leaks on top of the engine (from the small metal tubes/connections). Temp is steady on the gauge and where it should be.

He did note that the drivers side upper hose has a lot of crud built up near one end (passenger side hose was changed last summer due to a split) - possible slow leak there? it has been nearly a month since the last occurrence, suggesting a very slow leak.

Current plan is to change the drivers side upper hose (which we have on hand), top everything up and see how things go.

not really sure how or why the overflow hose came off tho... that one is a puzzler.

just wanted to make sure you were not using an aftermarket thermostat,  they are all garbage, and oem is the only way to go  oem on left, motorad on right

Oh, we know better than that, Turbodog. and thus far, the thermostat has not been changed (we do have one handy if needed- ordered back in Dec when this first became a problem)

hoping it is just a slow leak at that upper hose... overflow bottle has been cleaned up (was kinda grimy, so hard to read) - everything will be topped up and monitored closely for a while.

 

2 minutes ago, heartless said:

Oh, we know better than that, Turbodog. and thus far, the thermostat has not been changed (we do have one handy if needed- ordered back in Dec when this first became a problem)

hoping it is just a slow leak at that upper hose... overflow bottle has been cleaned up (was kinda grimy, so hard to read) - everything will be topped up and monitored closely for a while.

 

awesome!  sounded like it had an air bubble behind the thermostat

 

1 minute ago, turbodog said:

awesome!  sounded like it had an air bubble behind the thermostat

an air bubble would have manifested a lot sooner, i would think.. it has been nearly a full month since the last episode.

Just now, heartless said:

 

an air bubble would have manifested a lot sooner, i would think.. it has been nearly a full month since the last episode.

maybe,  my brother had an air bubble in his bmw for almost a year

A slow leak will slowly introduce air into the system, and the smaller the bubble, the smaller the symptoms. So it's possible.

 

I'd definitely pressurize the system and look for other leaks.

at this point, trying to just keep it nursed along until warmer weather.

He knows now that he needs to keep a closer eye on things - checking at least once a week to stay on top of it.

We did rent one of those cooling system pressure testers last summer (when we found the one split hose) and checked all of the vehicles while we had it (the kit had a deposit of over $250) - we were concerned about the radiator at the time.. thankfully it was just a hose. also found I needed a new radiator cap, lol, so it was a worthwhile thing.

But yeah... might want to rent that kit again and verify