Toyota Highlander heater issue

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  #1  
Old 04-02-17, 06:41 PM
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Toyota Highlander heater issue

My wifeís 2006 Toyota Highlander Hybrid 3.3 liter V6 has developed an issue with the heater. If she sets the heater output to achieve a comfortable cabin temperature at highway speeds and slows down to drive on local roads at 30 or 35 mph the heater output turns cold. She needs to readjust the temperature setting. Or if she drives again at higher speeds the heater output warms up again.

I checked the coolant level and its fine. I checked whatís involved in removing the thermostat. The Toyota manual lists 29 steps to remove it. That seems like a major nuisance. My third suspicion is a clogged heater core. Back flushing it seems like a lot less work than replacing the thermostat. Is there any way I can ascertain whether the thermostat or heater core is the problem? The temperature gauge indicates a normal temperature so I'm inclined to suspect the heater core. The car has 212,000 miles on it and has had the coolant changed only once. Iíve back flushed heater cores on other cars so I have the necessary hoses, funnels, etc.
 
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Old 04-03-17, 05:09 AM
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I've seen water pump impellers wear to the point where they can't pump water efficiently and cause symptoms like yours.
Good luck.
 
  #3  
Old 04-03-17, 05:21 AM
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The car has 212,000 miles on it and has had the coolant changed only once.
That is way too many miles for only one coolant change. I'd flush the entire system and assuming the thermostat is original - replace it while you are at it!
 
  #4  
Old 04-03-17, 06:29 AM
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So were those impellers made of metal or plastic? I recall the plastic impeller on my Audi water pump separated from the drive shaft at 62,000 miles which caused a catastrophic failure. I'd be surprised if a metal impeller would wear away, but then I'm surprised a lot. I'll be changing the timing belt, tensioner, idler pulleys and water pump soon. So I'll get a look at it then.
 
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Old 04-03-17, 08:36 PM
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OP, it is actually normal, let me surprise you.
It's a hybrid.
Hence, engine does not run all the time to maintaine comfortable heat. It turns on and off, off is a lot at low speeds and on back roads. hence, oncoming air flow cools down radiator - and results in colder coolant.
As I have HiHy too. Well familiar.
On TCH, Toyota Camry Hybrid, I have PTC heater mounted right before the heater core. Factory design. THAT warms up air and coolant in less than a mile. Why they didn't do same on HiHy - beats me.
 
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Old 04-04-17, 08:50 AM
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ukrbyk,

Our HiHy's must be different. If what you describe were the case we would have had this issue all along and we haven't. It developed this winter. The only time this vehicle runs solely on the electric drive motors is in reverse and when driving at really low speeds, like 5 mph. Anything faster and the gasoline engine kicks in. The hybrid system provides varying amounts of electric assist depending on the roads but the gas engine is running almost all the time. This car gas the so-called intelligent all wheel drive system--I don't know if that changes the picture in any way. Anyway, the gas engine turning on and off is not the cause of our problems.

I know that PTC heaters are used in plug-in hybrids and all-electric vehicles. I'm not sure our vehicle even has a PTC heater. If you have the vehicle on and stay parked for a while in winter the engine cycles on and off to keep the cabin temperature comfortable.

Thanks for your comments.
 
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Old 04-04-17, 09:15 AM
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In principle, our vehicles are identical. I have two hybrids and know them rather well.
1. if your vehicle 'suddenly" developed this symptom, for the year, I'd start with checking on engine belt, which you should have one and only, as your AC comp is electric and you have no alternator. PS is electric also.
2. not asked for observation. Something is really wrong with that car. The way you describe how HSD operates, it does not really operate at all the way it should. ICE should kick in only past 42mph under moderate acceleration. And should turn off the very moment speed drops past 40 or so in rolling condition.
So something not right. You may want to consider greenhybrid forum as they have Georgiahybrid as mod there, who is HSD tech and he helps many owners with very professional advice.
Either way, that vehicle is not working the way it should.
 
  #8  
Old 04-19-17, 07:50 AM
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I just happened to read about heater/temp control issues in Highlanders. The internals of the temperature control knob can become loose and cause the wiring from the knob to the circuit board to break loose from its solder connections. It can cause intermittent contact leading to temperature fluctuations.

No idea if that's your issue, but it might be worth looking in to.
 
  #9  
Old 05-31-17, 06:02 AM
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And the problem is.......

.....I have a coolant leak. When I earlier reported that the coolant level was OK I was looking at the coolant level for the inverter. I did not realize there are two separate cooling reservoirs, one for the gas engine, one for the inverter. I added coolant and the heater now works as it used to. I spend so little time working on this vehicle that I'm not all that familiar with it. I haven't yet confirmed the location of the leak but I strongly suspect the water pump. I notice a stain on my garage floor on the passenger side of the car where the water pump is located. And it has 212,000 miles on it. I'll be doing the timing belt/water pump/idler/tensioner soon.

Also, ukrbyk is correct as to when the engine kicks in. I rarely drive the car. My wife occasionally watches the power flow screen and she says the car behaves exactly as ukrbyk describes. Shows you what I know!

Thanks to all for your ideas and information.
 
  #10  
Old 05-31-17, 07:56 PM
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Aha!
yeah, owning two hybrids gives me some know how.
Camry hybrid first gen had bad spell of pumps going south. They fixed them in 2010 developing a new pump style. I had mine replaced under warranty. But I noticed no complaints on that from HiHy owners.
Hey, you are welcome. Don't forget to bleed the system.
Btw, look for pink "beard" on pulleys and up on the hood insulation. Looks like pink crystals mounds. That's bulletproof sign of pump leaking.
 
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