First check:
-- Remove the key from the ignition.

-- Go beneath the radiator and unplug the temperature switch installed in the bottom of the radiator, near the lower radiator hose. Unplugging the switch simulates a high temperature condition. This is not intuitive, due to the logic circuit the cooling fan electrical system uses.

-- Put the key in the ignition and turn it to "On" (engine not running).

-- Do both fans come on, and in high speed? They should. Report back here.


What year is your Rav4?

 

2000 fwd, the fans do come on high when that is disconnected and the switch is new a week ago.

 

I read that you are playing with the fuses but have you considered the relays that are in the circuit?

 

2000 fwd, the fans do come on high when that is disconnected and the switch is new a week ago.

Good. This means the relays are working correctly.

Who is the manufacturer of the new temperature switch?

Please test the old temperature switch and the new temperature switch. For instructions on how to test the switch, go to Elle's 1996-00 Toyota Rav4 Site and download the guide titled "Cooling Problems." In this guide scroll down to the section that gives tests you can do on the temperature switch.

Next, run the engine and feel the top radiator hose and the bottom radiator hose. Is there a large temperature difference? If so, the thermostat may have failed shut. When the thermostat fails shut, the coolant temperature at the temperature switch will tend to stay low.

When was the thermostat last replaced on this Rav? Was a Toyota thermostat used? Was the thermostat installed with the jiggle valve in the correct position?

Fuses do not have polarity.

 

Carquest Premium Engine Cooling Fan Switch from Advanced Auto.

I tested the new switch and the old one, the old one was not working. The new one did work prior to install, no logical reason it would stop working but I can test it again installed easily enough tomorrow.

When I make the fans run with the AC on, it cools to normal operational temperature, thus the thermostat is not the problem.

 

best to use the toyota branded switch.
or the import direct is ok but not as good as the toyota.
Import Direct Ignition 2 Terminal Cooling Fan Switch - 17-1477

 

What device trips the relays to run the RDI fan?

 

I am going to inspect the thermostat, maybe the bottom hose is not getting hot enough, even though it's hot, it's not as hot so Curses.. I have to pull it out.. thank you for your patience, I will get back after inspecting the thermostat..

 

hummm
did they get the wrong part in the box?
maybe you got a gauge sensor and not a thermal fan switch?
it happens in the real world.

check the part numbers on the switch and make sure they match.

 

Q. -- Please confirm once again: With the A/C off; temperature switch unplugged; the key in "On" (but engine not running); do both fans come on and in high speed?

A. Yes

-- I disagree about the absent thermostat not fouling up diagnosing here. For example, the coolant system might be full of air and need a purge. With no thermostat, and air in the system, the temperature switch's probe might stay too cool to open the switch, but the engine could still overheat.

A. I am aware there may be an issue and use a radiator fill kit like the ones they sell at Harbor frieght to remove air from the coolant systen to reduce and chance of air being the issue..

I am getting a thermostat today to be sure

Q. -- Only buy an OEM thermostat or the correct Kuzeh thermostat. This is important. If you need part numbers, ask. Also the thermostat has a jiggle valve which must be oriented correctly when installing the thermostat. If you do not understand, ask.

A. I am aware of the directional flow within the coolant system and that the temperature rating on the thermostat must be correct for a hot environment like where I live, and must be installed in the correct position.

i test everything before install, and will test to be sure it opens at the correct temperature.

Q. -- I do not know what you mean by "cycle through" hi/low speeds. To use this forum effectively, I think the user has to be very precise.
[/QUOTE]

A. When I turn the AC on, both fans come on high speed, then switch to low speed when the compressor is not on, then back to high speed, etc.

Note: thank you for your time..

One Relay tested bad originaly, the 5 fin,(fan 2) so I replaced it, it tested perfect before install.

 

A. When I turn the AC on, both fans come on high speed, then switch to low speed when the compressor is not on, then back to high speed, etc.

Got it. I do not like this. In the wiring diagram, notice that there is an "AC Single Pressure Switch" in series with the coolant temperature switch. If the pressure switch is acting up, this may cause the symptoms you are describing. One can bypass the pressure switch (for ten seconds, say) and see if this cycling you describe goes away.

But first, I advise installing an OEM or Kuzeh thermostat and purging the coolant system of air. Get things back as normal as possible (with the correct new thermostat, with the thermostat jiggle valve "clocked" correctly, and a temperature switch that for now, you think is working). Then report back any changes in the performance of the cooling system.

Would you please post the part number of the thermostat you buy?

Can you give some history on this Rav4? How long have you owned it? Has it always had this problem? Or was it running fine for awhile and then this overheating started?

Did a prior owner leave the engine without a thermostat? I have some guesses why someone would do this.

You are welcome. Good for you for hanging in there. If I post anything that is confusing, feel free to ask for elaboration.

 

sweet6b9, got it. It helps to know that this Rav4 was recently acquired, with the condition uncertain, so assume nothing, and be braced for surprises (like the absent thermostat).

 

Ok, the thermostat that was in the car tested good, I have a replacement in now either way but I'm going to hang on to the old thermostat in case I need it later.

The hoses are replaced also, but the fact the old thermostat opened easily means that was not the issue. The hoses were old but still working so that was not the issue, it still boils down to the signal not making it to the RDI power engaging the fan...

sooooo, I am going to pull the Relays and re-test them before beginning the wire tracing process in the Fuse box to find out where the disconnect between b the relays or the last relay in the RDI side of the electrical path to activate the fans.

If I understand this correctly both fans run in low or high. Not one fan just for engine cooling?? Is that correct??

 

I got replacement hoses and a thermostat that I personally tested, it opens just over 180 degree

I will install tomorrow, but it seems unlikely that when the car is sitting parked for my tests that the ambient wind could cool the engine enough, so that's a false idea, I am going to double check the relays to be sure I didn't break the new one with the first start after install..

just to be sure, test and retest.. then it's on to testing the wires..

 

-- I guess I misunderstood about the thermostat. I guess you are saying it was always present, except when you were doing some kind of check.

-- Did you install the thermostat so that the jiggle valve is in the position shown below?

-- Do both your thermostats have a jiggle valve, as shown below?

The jiggle valve is at about the 5 o'clock position in the photo above.

-- Correct, both fans run at the same speed at all times, that speed being either Off, Low speed, or High speed.

-- Did you purge the air from the system? What technique did you use?

-- Since both fans come on in high speed with the coolant temperature switch unplugged; the key in On (engine off); and the A/C off, I continue to maintain that the relays are fine.

-- I have several questions to help narrow this down, but I am finding communications very difficult.

You will figure this out.

 

-- I guess I misunderstood about the thermostat. I guess you are saying it was always present, except when you were doing some kind of check.

Reply: No, I was looking in the wrong place, The thermostat was under the alternator. I found it and the new one does not have a jiggle valveit wss in the 12:00 position in the car. I will put it back in since it works and has the valve.. thank you!!

-- Did you install the thermostat so that the jiggle valve is in the position shown below?

-- Do both your thermostats have a jiggle valve, as shown below?

The jiggle valve is at about the 5 o'clock position in the photo above.

-- Correct, both fans run at the same speed at all times, that speed being either Off, Low speed, or High speed.

Reply: Got it!

-- Did you purge the air from the system? What technique did you use?

Reply, not yet, and now it will be longer still because I am going to replace the jiggle valve thermostat since it works fine. I will use the system I have that works like the one from Harbor freight.


-- Since both fans come on in high speed with the coolant temperature switch unplugged; the key in On (engine off); and the A/C off, I continue to maintain that the relays are fine.

Reply: I agree, so I should follow the electrical flow for the RDI fan only when the AC is off and make sure there is continuity between the sockets in the Relay box

-- I have several questions to help narrow this down, but I am finding communications very difficult.

I know, I left out the whole location of the thermostat thing after finding where it was supposed to be.

You will figure this out.

 

Guys I didn't read thru all the testing and analysis so don't jump on me but my first thought when seeing the title was possibly a bad radiator in need of replacement. I've had that happen on two cars, a Plymouth 340S Barracuda and a Toyota Tercel Wagon.

 

Thanks but I dont think so..
Please elaborate what you mean by 'bad'?
Do you mean clogged, I drain and refill it easilt..
It works just fine to cool when the fans kick on.
It is undamaged.
It has flow and I bleed it using a fail safe system.

The problem is the RDI fan is not coming on at the half way mark on the gauge.. it continues up and starts overheating. No fan.

The engine cooling works just fine when the RDI fans work, so no.. not the radiator.

I have tracked the problem down.
The switch is not opening all the way at the correct temperature.

The rating on this switch is 180, or 176, but it needs to be lower for it to open at the correct temperature, two new switches provided the same reading, when the gauge is 3/4 of the way up, (almost to the red) the switch is only providing 4.6 Ohms resistance but should be Infinate just above the half way mark to make the RDI fans come on.

I am unsure how to resolve this issue other than going directly to Toyota to get help.

I got the exact part that was suggested in this feed but It tested today at 4.6 Ohms when it should already be completely open and infinite in resistance/Ohms..

Ultimately, It could be a bad switch, or the wrong temp rating for my vehicle.. Import Direct OE

 

sweet6b9, try this: Unplug the coolant temperature switch. With the switch unplugged, the fans should run anytime the Rav4 engine is running. Take a long test drive. Do not use the air conditioning. Does the engine overheat? (If the engine starts to overheat, pull over and let it cool down.)

 

Yes, with ignition on, the fans run if the switch us unplugged confirming the RDI fuse and relays and all Interconnected wires are working. The switch must open at the correct temperature in order to turn the fans in but it is not completely open at the time it should be 4.6 Ohms is at the point of overheating. It's more like 2.6 Ohms when the gauge shows half way (or the normal Operating temp range per the gague)

I will do the test again using boiling water.. following the instructions on the image you sent

 

a couple of questions
are you using a funnel system like this one for refilling?
they are needed to get all of the air out of the system

and exactly what make and model is your ohm meter? please post a pix of the meter.

for basic testing on cars and trucks this one is ok and will do some advanced testing

i do not like the readings you are posting.
something is up on the switch's or the meter.

when cold it should be at zero ohms or dead short.

and when over 200F it should read open or OL on a digital meter depending on the exact make of the meter.

unless it is measuring your finger tips as they are wet and will conduct some.
best to use clip leads like these when bench testing sensors
and do not submerge the electrical connections as the test water will conduct for a bad readout.

 

This issue is officially closed!!
However now there us a new sound, sounds like bearings From the same spot they worked to replace the pump. Once it cools down I will inspect it closer for rubbing parts... that will be a new post about fixing the repair they did...

 

make sure they got the tension for the timing belt right.
over tight makes more noise.
i needs to be in the Goldie locs zone as just right.