Lackluster heat even after professional flush

[Giraffe]

Hey all. I recently had my car professionally flushed since I didn't want to put Wichita Falls water into the engine. The morning temps have been a tad cooler and I've tried out the heat but am still only getting cool air out of the vents.

Are there any known issues with the mix/blend doors or whatever mechanism it is that adjusts the vent air? I'd like to see if I can get this working by the time it gets really cold.

[turbo2256b]

Do you have automatic climate control?

[Giraffe]

Negative. Manual.

[gadget73]

does it have the proper thermostat? Colder thermostat makes for crappier heat.

[GM_Guy]

When you slide the temp lever from one side to the other, do you hear the door in the plenum slap when it hits end of travel?
If yes, at least the hot/cold door is moving.

Is the temp lever stiff, or does it move really easily? option B would be a negative to the first question, and your cable is probably no longer attached to the blend door arm. (take off the glove box door).

Do you get any inkling of heat? If yes, have you replaced the heater core before ending up with poor heat? If yes, guess what, take it all out and put that foam sealing strip around the heater core, and stack it if there is any gaps around the core. ANY cold air getting around the heater core is going to give you poor heat.

Got a thermal temp gun? If you do, makes checking out the thermostat easy without taking anything apart just to look.

And what makes you think Witchita Falls water wasn't used during the flush if it was done in a location serviced by the same water system? ;-)

Alex.

[VicCrownVic]

Even with a professional engine flush, I'm not sure that the heater core would benefit unless they also flushed it directly.

The Ice Car had poor heat when I got it and was great after I flushed the heater core but it would revert back to crappy hardly warm heat in as little as a month.
I've had good heat for the past 3 or 4 years now after replacing the heater core though.

One thing I found when my heater core was clogged is that I could drive around for a while with the heat off which would actually build heat in the heater core. Then I would turn it on and briefly have noticeably warmer heat. It wouldn't last long enough to make a difference in cabin temp since airflow across the heater core would cool it right down, but it did help me verify that it must be a clogged heater core. If the heater core is too plugged up this may not work, but it's an experiment worth trying to help diagnose the issue.

[Tiggie]

My lack of heat performance:


Sounds like yours may be a blend door though. Even with a blown thermostat, I could build enough heat in moderate weather to be comfortable. Only below freezing did I notice a difference in heat output.

[Giraffe]

does it have the proper thermostat? Colder thermostat makes for crappier heat.

It has a Motorcraft stock replacement thermostat I installed when I resealed the top end in December.

When you slide the temp lever from one side to the other, do you hear the door in the plenum slap when it hits end of travel?
If yes, at least the hot/cold door is moving.

Is the temp lever stiff, or does it move really easily? option B would be a negative to the first question, and your cable is probably no longer attached to the blend door arm. (take off the glove box door).

Do you get any inkling of heat? If yes, have you replaced the heater core before ending up with poor heat? If yes, guess what, take it all out and put that foam sealing strip around the heater core, and stack it if there is any gaps around the core. ANY cold air getting around the heater core is going to give you poor heat.

Got a thermal temp gun? If you do, makes checking out the thermostat easy without taking anything apart just to look.

And what makes you think Witchita Falls water wasn't used during the flush if it was done in a location serviced by the same water system? ;-)

Alex.

I hear a slap, but it's more audible when bringing it back to the cold side. There isn't any real inkling of heat at all even when up to operating temp. The temp level moves fine, but I did have to oil it up a bit after I bought the car as it was stuck pretty good.

I haven't replaced the heater core yet. I kind of don't want to until I put a new engine in it. God only knows what gunk is still in there waiting to get dislodged and clog a brand new core.

I just took their word for it that they used distilled. Who knows? Haha.

Even with a professional engine flush, I'm not sure that the heater core would benefit unless they also flushed it directly.

The Ice Car had poor heat when I got it and was great after I flushed the heater core but it would revert back to crappy hardly warm heat in as little as a month.
I've had good heat for the past 3 or 4 years now after replacing the heater core though.

One thing I found when my heater core was clogged is that I could drive around for a while with the heat off which would actually build heat in the heater core. Then I would turn it on and briefly have noticeably warmer heat. It wouldn't last long enough to make a difference in cabin temp since airflow across the heater core would cool it right down, but it did help me verify that it must be a clogged heater core. If the heater core is too plugged up this may not work, but it's an experiment worth trying to help diagnose the issue.

I'll have to try that experiment.

[GM_Guy]

Disconnect the hoses for the heat core, get a couple scraps of hose, one to the ground from the heat core, and the other to your garden hose and flow some water through it (NOT FULL BLAST!!). See if any gunk comes out, and keep flowing water til its clear, then switch sides and do the same.

Alex.

[jaywish]

Is the hose hot going into the core?

[Giraffe]

I'll have to check the hose heat next time it's running. I couldn't tell you right now.

I'll try the scrap hose thing soon. Too bad I just threw away about five feet of ¾" heater hose when I cleaned out my garage.

[jaywish]

Check the temp in and out of the core before the flush.

You can use existing heater hose to do the flush. As long as one is disconnected and use the other to connect the garden hose. Just more water in the engine compartment if you don't aim a hose at the ground. As Alex said not full blast.

[DerekTheGreat]

That or just run radiator flush through the thing, in the opposite direction the water pumps from the factory. That helped with our '88 GMC when we had it. Heat barely worked in that, especially when temps were below freezing. After flushing 2 or 3 times, hot as an oven.