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Discussion Starter #1
Hi all, newbie here.
My ride:
2010 Camry 4Cyl 2.5L SE

Issue: Heater only work in park mode but not while driving. This one stumps me big time. I flushed my radiator with a prestone kit, new fluid, changed out thermostat (yes, I did performed boiling water test prior to installation - opens at 180F fine, no issue there), and even changed out the water pump too. I bleeded air for over 3hrs. No luck. I'm feeling like a bump now, totally lost on this one. Can't be the heater core, it flushed fine. No clog there. Flushed radiator fine, no clog there too.

In idle, both inlet and outlet hoses to the heater core were measured at 135F, cabin temp at 120F. So I got decent heat. The fan even turns on when the engine bay gets too hot. Upper radiator hose measured 160F, lower radiator hose measured 140F. No over heating issue. The gauge stays slightly below center at all time.

Now, I go for drive. 40mins later, it starts to blow cold air so I pull over. Felt the upper hose, measured 160F, lower hose 95F! Urgggghhh heck is going one? No fluid leaks, checked double checked trippled check, - no leaks. If I stay idle long enough it will heat up again and thermostat will open letting hot coolant through and temp will rise back to 140F and I will eventually get heats inside the cabin again. But as long as I'm driving, the lower radiator hose will always always stay cold.

I'm getting the opposite of most people when they experience this symptom, my heater only work in idle mode. Gosh what on earth could've gone wrong? Please help:)
 

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Discussion Starter #2
Could it be possible my blend door went bad so it sent signal to the engine to stop coolant flow to lower radiator hose? I went on Amazon it shows they have 2 types:

Which one do I need? These 2 are different. How many blend door does a 2010 with manual climate control need? Do I need both or just one? After watching a handful of YT videos, I don't hear any clicking sound. How do you tell if a door went bad?
 

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Camry_owner
2003 Camry LE 2.4L
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172 Posts
If the heat works on idle but not while driving , something is not wrong with the blend door actuator. Probably wrong or faulty thermostat were installed. Or your climate control unit faulty.
 

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Discussion Starter #4
Which one do you think went bad? I listed 2 types above? Please hint me so I can make the purchase thx
 

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Camry_owner
2003 Camry LE 2.4L
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Which one do you think went bad? I listed 2 types above? Please hint me so I can make the purchase thx

How many mileage on the car?

May be your water pump bad or bad thermosatat. That is why when you drive the car, the coolant is unable to circulating through the system properly, since not radiating any heat. Or may be the thermostat defective and stuck open, so the engine is not heating up properly.

I will suggest you to check your water pump or thermostat first.
 

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Discussion Starter #6
How many mileage on the car?

May be your water pump bad or bad thermosatat. That is why when you drive the car, the coolant is unable to circulating through the system properly, since not radiating any heat. Or may be the thermostat defective and stuck open, so the engine is not heating up properly.

I will suggest you to check your water pump or thermostat first.
120K, I already changed out my WP, thermostat, radiator cap, flushed & changed coolant, and bleeded air for 3hrs. See my initial post. I think your previous response is closer to the money, I just don't know which one of 2 blend air is needed. They're not cheap. The circulator blend air is hard to get to.
 

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Camry_owner
2003 Camry LE 2.4L
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172 Posts
120K, I already changed out my WP, thermostat, radiator cap, flushed & changed coolant, and bleeded air for 3hrs. See my initial post. I think your previous response is closer to the money, I just don't know which one of 2 blend air is needed. They're not cheap. The circulator blend air is hard to get to.
since they are not cheap just see if you can find one used from ebay or local junkyard if you think those two parts might be the issue. I have never faced this kind of issue with any car so far. This is strange issue. The issue is the coolant not circulating through the engine properly or thermostate stuck open , so engine not heating up and you not getting hot air while driving. It it may be your climate control panel faulty.

does your engine coolant temperature gauge stay steady after engine warms up? Do you have check engine light on? You can take your car to any autoparts store and get it scanned for free. You should know the code if you have check engine light on.
 

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Discussion Starter #8
I know, my situation is weird. So I covered all the basics. This one is a little tricky since Toyota did decided to go with electric control valves for most of their stuffs so this is new to me. I'm used to manual push valve and throttle cables, this car doesn't have any of that.

The gauge stays slightly below center of H & C which is normal so I don't think it's a bad sensor. No engine light. My Z13 scanner returns no error code. I'm positive my t-stat is good, I tested it 15x times before the installation in boiling water - I took crazy measurements too. And the old water pump turns out to be in perfect condition, interior is nicer than my brand new one, but since I got that far I just went ahead and change it anyway which is why I'm low on money now :)

I noticed a bizzare thing, maybe you can help me with this one. I have a manual climate control, the 3rd knob to the right where switch to different circulation modes. Right after startup, I noticed a strange behavior never seen before. Right after I crank on the engine, this knob's yellow LED will blink for about 10s before the blower motor turns on. Does your car do that??? Is this even normal?
 

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Camry_owner
2003 Camry LE 2.4L
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172 Posts
I know, my situation is weird. So I covered all the basics. This one is a little tricky since Toyota did decided to go with electric control valves for most of their stuffs so this is new to me. I'm used to manual push valve and throttle cables, this car doesn't have any of that.

The gauge stays slightly below center of H & C which is normal so I don't think it's a bad sensor. No engine light. My Z13 scanner returns no error code. I'm positive my t-stat is good, I tested it 15x times before the installation in boiling water - I took crazy measurements too. And the old water pump turns out to be in perfect condition, interior is nicer than my brand new one, but since I got that far I just went ahead and change it anyway which is why I'm low on money now :)

I noticed a bizzare thing, maybe you can help me with this one. I have a manual climate control, the 3rd knob to the right where switch to different circulation modes. Right after startup, I noticed a strange behavior never seen before. Right after I crank on the engine, this knob's yellow LED will blink for about 10s before the blower motor turns on. Does your car do that??? Is this even normal?
can you show a picture of the knob that turns yellow? Not normal to blink. Should stay solid. Blinking usually correspond to some kind of fault. Which knob or switch doing this, if you can show the unit with the knob, would be helpful. Mine strays solid.


are you looing coolant or water slowly while driving?

  • Faulty Heater Core
  • Malfunctioning Thermostat
  • Inoperative Blower Fan
running idle tepperature should be around 180-190 deg F
 

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Camry_owner
2003 Camry LE 2.4L
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172 Posts
See animated gif attached

Yes that knob not suppose to flash/blink like this. Some kind of relay issue. I found one issue like this for AC , look at the video, but your issue is related to Heater I know. You might be right. When you switch/turn the knob mode, it does not switch. Does it make any whiny noise when you turn that knob? That motor/ switch may be stuck.

Also check if the AC Blower Motor Resistor is good or not. Cheap parts, sometimes it goes bad.

1. Check your blower motor if it is working or nor
2. Check your thermostate (faulty)
3. Check blower motor resistor.

these are the posibilities I can think of for your car not heating up while driving.

 

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First unlike the old days when you had a valve under hood that opened and closed to let coolant into the heater core most just flow constantly no valve. You always have coolant circulating through the heater core today. Re-check your coolant level.

I take it you left the rad cap off let it come up to operating temp. brought it up to 2000-3000 rpms to get air out for a few minutes? I prefer to top up with it at 2000 rpms put cap on and shut it off. Oh and even though most systems do not have heater flow control valves I still turn the heat and fan on when I am feeling the radiator old habits die hard.

Good for you for checking that the thermostat opened at temp. before installing so many do not do this today.
 

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Discussion Starter #13 (Edited)
Inchina,
Interesting, I looked at this box under the hood ...no relay dedicated for heater, my AC seems to be working fine. It still sux when ambient gets over 100F, anything below is okay. I did changed all the fuse labels "heater" from inside the cabin by the emergency brake. When I look at your suggested location, it mentioned something about 50A for HTR. Is this part of the heater? Does this look right, it ties some weird bizzare looking multi-fuse chain - I have never seen anything like this before:
Yeah I'll check the blower resistor too. My blower is working though, it blows strong but something is telling me my door is partially closed, even in idle, both inlet and outlet to the core were measured at 140F but I'm still getting 109F at the vent at max 100% heat setting....hmmm, could my blend (not circulatory) door be stuck?

1975,
Yes, I bleeded air at ground level. Did not bother to jack up the vehicle this time since my funnel is pretty tight, it holds tightly no leak so I just let it idles for 3hrs. I did rev up the engine to 2K for about 5mins but I didn't noticed much improvement. I did noticed improvement after idling for 1hrs 30mins it blurps more frequent.
 

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OE thermostat? If not, get one from the dealer and install it.
OE waterpump or Aisin? If not, get one from the dealer and install it.

Hate to say it, if you lose heat while driving, you might be getting air in the system. Test for blown head gasket, and pressure test for leaks.
 

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Touch 2 hoses, going to heater.
Sometimes heater cores get clogged and need garden hose flush.(both ways)
Infrared thermometer is great for diagnosing radiators/thermostats/heater cores/engine overheating.
I paid dealer mechanic $50 to diagnose overheating Corvette engine, he couldn't. I bought thermometer, it took me 5 min to diagnose bad brand new thermostat.(it was opening half-way)
 

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Camry_owner
2003 Camry LE 2.4L
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172 Posts
It could be faulty thermostate, waterpump, or clogged heatercore. Last thing you should check is headgasket.

Autozone will let you rent the head block test kit for free. You will just have to buy the fluid which is only $5-6 I guess.
 

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Camry_owner
2003 Camry LE 2.4L
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172 Posts
also check if you are losing any engine coolant or not. Check if you have any visible water/coolant leak somewhere or not.
 

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Camry_owner
2003 Camry LE 2.4L
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172 Posts
If you have recently replaced the thermostate and coolant, than you need to bleed the air properly. Air in the system might cause this cold air issue.
 

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Camry_owner
2003 Camry LE 2.4L
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172 Posts
For a heating system to work properly, your car must have the appropriate coolant level in the engine, a perfectly working thermostat, a cooling system without leaks, and a working heater core.

My best guess would be bad thermostat. Buy one genuine OEM Toyota thermostat. Not expensive around $15-$20 most. And than bleed the air properly.
 
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