Trouble with heater

Greetings I have an 06 Matrix XR, 109000 kms, FWD, Automatic. Recently I have been having issues with the heater. It only seems to blow hot air when the engine is under load (ie when the car is in motion). When idling in gear or in park it only blows cool air. If the car is in park and the engine is rev'ed, the air warms up. Observations: The temp gauge is functioning properly (seems rule out temp sensor) The engine is not running too hot or too cold (seems to rule out thermostat) The engine fan appears to be working properly (ie it turns on and off as normal, seems to rule out sensor) There are no coolant leaks, coolant not due to be replaced for 80K km The heater fan is working properly It does not seem to make a difference if the a/c is on or not. Recirculate setting is only slightly warmer. A/c works fine to cool. Thanks in advance for your help.

Reply 1 : Trouble with heater

You may have a small restriction in flow thru your heater core. Higher engine speeds give you more flow pressure, so more heat and then when idling, the pressure is lower and less flow thru core.

My only thought ,given the info you provided.

Reply 2 : Trouble with heater

i have the same trouble in my 2005 XRS won't defog glasses passe -15 degrees

Reply 3 : Trouble with heater

Quote:

Originally Posted by MR2Jedi You may have a small restriction in flow thru your heater core. Higher engine speeds give you more flow pressure, so more heat and then when idling, the pressure is lower and less flow thru core. My only thought ,given the info you provided.

I'm having the exact same problem with my 2007 Camry. I can't see how it has anything to do with a slightly clogged heater core. When you pull to a stop it blows real warm. Once stopped, the air starts to cool down. Once you take off the air immediately gets warm again. You can get the same results if when stopped, place it in neutral and give it just a little gas and it gets immediately warm. The other reason I don't think it's a blockage is the antifreeze looks good. The car also doesn't do it ALL the time, just more times than not here lately.



I'm wondering if it has something to do with the blend door like when it's at idle the blend door can't hold itself closed on the cold side. Maybe low voltage. I did have to clean the positive battery post this Fall. I have never opened a hood to see a positive post with more corrosion piled up. It looked like a multicolored snow cone. It came out of nowhere. I had to put distilled water in it and I also charged it with a 3 amp charger for a day.

Reply 4 : Trouble with heater

You guys using Toyota Pink coolant?

Reply 5 : Trouble with heater

Quote:

Originally Posted by shortlid You guys using Toyota Pink coolant?

Thanks for responding. It's using the coolant that Toyota put in it from the factory. I'll have to check the color for sure. It looks clean, whatever it is. I know what rusty brown coolant looks like though, which indicates a bad thing and in need of replacing. The car has about 51xxx miles on it.



Never have had a car behave like this just when sitting at idle. The car seems to run fine mechanically. The dash squeaks and rattles in this cold weather. The sunroof has always rattled at different times which is annoying as heck. I'm dissappointed, to be honest, with this car. The recalls and everything. I paid a premium for the car because it was a Toyota. They have problems like all the other car brands have and now they know it. The problem discussed here is a new one for me. I would bet Toyota has seen it quite a bit since it appears to be happening with other models also.

Reply 6 : Trouble with heater

Quote:

Originally Posted by MR2Jedi You may have a small restriction in flow thru your heater core. Higher engine speeds give you more flow pressure, so more heat and then when idling, the pressure is lower and less flow thru core. My only thought ,given the info you provided.

Quote:

Originally Posted by bigblu91 I'm having the exact same problem with my 2007 Camry. I can't see how it has anything to do with a slightly clogged heater core. When you pull to a stop it blows real warm. Once stopped, the air starts to cool down. Once you take off the air immediately gets warm again. You can get the same results if when stopped, place it in neutral and give it just a little gas and it gets immediately warm. The other reason I don't think it's a blockage is the antifreeze looks good. The car also doesn't do it ALL the time, just more times than not here lately. I'm wondering if it has something to do with the blend door like when it's at idle the blend door can't hold itself closed on the cold side. Maybe low voltage. I did have to clean the positive battery post this Fall. I have never opened a hood to see a positive post with more corrosion piled up. It looked like a multicolored snow cone. It came out of nowhere. I had to put distilled water in it and I also charged it with a 3 amp charger for a day.

Wouldn't that be a small restriction? I never used the word clogged.

Reply 7 : Trouble with heater

Quote:

Originally Posted by MR2Jedi Wouldn't that be a small restriction? I never used the word clogged.

Sorry, for the misunderstanding. You're right, you didn't say clogged. You said "small restriction". If I had any restriction, I would think, the heater wouldn't cook me out when driving down the highway. That's been my previous experience with heater cores and restictions or clogs.



If your mention of a "small restriction" is a reference to airflow since you highlighted it in my post, I don't appear to have a restriction in flow(like the OP said also) because the blower and the air flow coming out of the vents seem to be normal. The only thing I can think of is that the blend door at idle is not being held closed on the cold air side.



As I said in my first post, it doesn't always do this. My wife has warmed the car in the morning several times before she leaves for work and at idle it heats up well then. It's just there are times it does what it does and it seems to be increasing frequency. I'd like to figure it out before it is all the time.



Sorry again for misunderstanding. I didn't realize you were generalizing "small restriction" to mean coolant flow OR air flow.

Reply 8 : Trouble with heater

These things can be such a pain. If they weren't buried in the dash, it would be alot easier .

Reply 9 : Trouble with heater

I wouldn't rule out a bad thermostat or low coolant level. Had a Chevy that did that same behavior, cool air at idle, but blows hot when engine is loaded. Never shows signs of overheating or overcooling - temperature gauge was right where it was supposed to be. Coolant reservoir tank was always full - so I assumed the cooling system was full. Cracked the cap and it was lower than I initially expected. Refilled at the radiator, made sure there was enough room in the coolant reservoir tank in case it was too full. Ended up being a combination of low coolant level, stuck thermostat, and bad radiator cap (spring was too strong).

Reply 10 : Trouble with heater

I have a rav 4 that has a similar problem, although on idle i have a trickle flow into the heater core, rap it up and i have great flow and good heat

Reply 11 : Trouble with heater

Quote:

Originally Posted by kmahorney I have a rav 4 that has a similar problem, although on idle i have a trickle flow into the heater core, rap it up and i have great flow and good heat

I'm curious, how do you know for sure you have trickle flow through the heater core? What symptoms does it show to draw you to that conclusion. You can see the flow through the core? Is there something that I'm not aware of that can show slow flow through the core at idle and then pick up immediately when a small amount of gas is applied. Just curious.



I've had plugged cores that produced no heat and restricted cores that produced less than normal heat all the time. It doesn't seem right that any blockage can cook you when just a little gas is applied and then cool down slowly when stopping and sitting at idle for a time.



Also, it doesn't always have a problem at idle. Yesterday morning, the car warmed up to full heat when started and left to run for a time before my wife left for work. She started to leave for work and she called me from inside our subdivision. There was a person stuck and blocking the road. We had some refreeze liquid from a recent snow melt off. She said the heater had warmed the car up just fine when idling in the driveway but when she stopped because of the road block the heat started cooling down. I told her to rev the car slightly in park and that warmed the car up. That just doesn't seem to indicate a blockage or restriction.



I'm open for a more detailed explanation to understand how you can know that the coolant is trickling through your core at idle without having a see through tube in the system to see the slowdown. Thanks for the response.

Reply 12 : Trouble with heater

Two options on watching the flow, either put a clear hose in or just pull of the input then the output hoses to see what the flow is. I was working on mine again tonight, i took the manifold off the top rad hose that feeds the input of the heater core. all looks well there. i am starting to suspect a pump issue. This pump has been replaced before and i wonder if there is some issue with it. normally pumps dont fail in this way, they just start leaking. I just dont have any where to go now. I am at a loss. My flow is low. My mechanic is even confused so i stopped taking it to him. He said it was the core, it is not...

Reply 13 : Trouble with heater

You may have a water pump problem. Was the coolant changed out the proper interval. Water pump impeller could of corrode or fallen off the shaft, causing very low water flow. If pump was replaced recently, cheap quality part was used causing premature failure.

See video.

You Tube

You Tube

Reply 14 : Trouble with heater

The pump has been at the back of my mind for a while but figured that would be last case scenario. And it seems like the people that have that issues have overheating issues. So i am not sure but i think it is very possible.



I do not know the history on this vehicle, but it looks like it has 20k. It has 141,000 and looks like new. The T belt has been replaced but don't know on the pump, some mechanics are bad about not doing the pump at the time of the belt. More work for them later, i guess.