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Heating not working for no obvious reason

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Hks

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Discussion starter · #1 ·
Hi all, I searched by and large without finding exactly what I need, so here I am looking for some guidance.

The ask: does anyone know how the internal heater works? More specifically, is there a valve somewhere that could get stuck in half open position?

The story: I bought an used RAV4.3 D4D 2.2 2007, in summer, and didn't check if the heater was working... stupid me. Winter lurkes and here I find that the hot air doesn't come out. Lukewarm at best. I search trouble codes and find that I needed to change the AC amplifier. Done, no error codes anymore, but the situation improved by just one or two degrees.
The water in the motor gets hot but doesn't seem to get as hot in the internal heater radiator. I thought of air pockets but after trying all I could to get them out, it seems that's not the issue after all...
Looking for any suggestion I can get...

Valerio
 
#2 ·
Hi,

Could be a sticking thermostat valve of the engine cooling system. Does the temperature meter show a temperature approx. around 90 degrees Celsius (not sure about Fahrenheit tbh) or is around 70 degrees. This would be an indicator for a stuck valve.
Hope this helps.

Best
Gerald
 
#3 ·
Possible causes for no cabin heat, ...
Stuck open thermostat in engine cooling system.
Low coolant level.
Stuck blend door in ventilation system.
Sediment build up in the cabin heater core.
Poor circulation from blower fan motor (cabin air filter).
Water pump faulty.
And something else I forgot.

If the engine gets very hot and the heat in the cabin is not good then usually the cooling system needs to be flushed. This would mean the heater core and radiator. There are store bought cleaner available such as CLR or radiator flush. Or, some use vinegar and water. Good luck
 
Discussion starter · #4 ·
Hi @GH2O , your advice was really useful to rule out the first doubt. Water reaches 90°C so the thermostatic valve must be working as expected.

@Avisitor, thanks for your input. I checked before turning on the fan and both pipes of the heater were at the same temperature. After a couple of minutes, the top pipe was cold and the fan would blow only cold air... so I'm guessing it's a radiator that needs flushing.

But is the water constantly circulating in the internal radiator, even when the blower is off? Isn't there another valve somewhere?

And, on a side note, why would the radiator get obstructed if the only things circulating inside is Toyota's own coolant?
 
#5 ·
Hks said:
@Avisitor, thanks for your input. I checked before turning on the fan and both pipes of the heater were at the same temperature. After a couple of minutes, the top pipe was cold and the fan would blow only cold air... so I'm guessing it's a radiator that needs flushing.

But is the water constantly circulating in the internal radiator, even when the blower is off? Isn't there another valve somewhere?

And, on a side note, why would the radiator get obstructed if the only things circulating inside is Toyota's own coolant?
Click to expand...
Yes, there should be a heater control valve on the inlet side of the heater core near the firewall. It can become obstructed and block coolant flow.

Although engineers try to keep everything to function well, corrosion happens. Rust on the underside of the vehicle. Corrosion on the inside of the radiator and heater core. Corrosion on the battery posts. As some say, stuff happens or is it life happens?
 
Discussion starter · #6 ·
@Avisitor , I learned the quote in Australia, so it was more mundane and colorful, but definitely "something happens".
However, jokes aside, I owned a number of old and very old vehicles and this is the first time I get a radiator with sediment clogging it, which tells me this is a particularly poor design (having this under 150.000km? Veeeery poor design) which I wasn't expecting from Toyota.

Anyway, I searched for the valve but I cannot find one single reference for it.
Below is partsuq with my VIN and pointing to the exact parts.


And if I search for the heater only 8710742170, none of the images or designs show any room for a valve... so my question keeps being: is there a valve at all anywhere in this design?

My next steps will be flushing it like a pro, hoping it doesn't need replacing as that's really hard work

Val
 
#7 ·
Buying used, one doesn't know what the previous owner put into the radiator. Tap water to save money?? That has more chance of causing corrosion.

I am sorry. So use to older cars. I do not know for sure if your Rav4 has a heater control valve near the fire wall. But, I found this video that might help??? May not be your issue.


Of course this may not be your issue. I am still thinking it is the heater core that needs flushing. Good luck.
 
Discussion starter · #8 ·
Hi @Avisitor, thanks for the vid, I will definitely look at it even if I solved the problem: flushed it with high pressure water In reverse and got a lot of sediment out. It was gray and jelly-like... don't know what can cause it. In any case, now works perfectly ! I can dry laundry in it now!

Thanks a lot for all your help :)
I owe you two pints

Val
 
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