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cooling fan doesn't turn on until hi-temp light
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completelyhis
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Jul 19, 2010, 9:32 PM
Post #1 of 13
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cooling fan doesn't turn on until hi-temp light
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2002 Toyota Echo w/175,000 miles.
the cooling fan doesn't turn on until the red temp idiot lite comes on. If I turn the AC on the cooling fan runs right away. I think that means that the cooling fan relays and fuses are good, right?
I suppose it is possible that the sensor that indicates temp could be wrong, making the idiot light come on when it shouldn't? Is there anything else I can look at? The car runs good and strong, FWIW
Thanks,
Ian
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Tom Greenleaf
Ultimate Carjunky
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Jul 20, 2010, 10:01 AM
Post #2 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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My guess is temp switch for engine cooling is just way too late or idiot light sender is way too early?
Make sure system is properly filled and isolate the temp switch for the fan. It could be clogged or malfunctioning - can't say. Just avoid overheating at all costs. Right in that if it finally comes on I would think electrically things are ok just not on time,
T
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completelyhis
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Jul 20, 2010, 2:13 PM
Post #3 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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Tom, thanks for the reply.
Some more research I did tells me that perhaps another issue my Echo has may be related to the overheating. I'll try to make the story short.
We took the car on a road trip. Some time after entering "death valley" the temp light came on, so we stopped running the A/C, and then even had to start running the heater. The temp light would stay off as long as we ran the heater.
Then we went on a long dirt road with a lot of "washboard" bumps that we were going fast on, along with following people on front of us who were kicking up a lotof dust. That was when the check engine light came on. The car ran fine the whole time, except for the over heating (not sluggish, running rough, or lacking power). a couple days later I was able to get the engine code read - it was something about low efficiency on the catalytic converter. They cleared the code...the over heating problem was still there, though mitigated by running the heater.
the check engine light came on 5 days later (maybe 500 miles or so). I haven't had a chance to read it, because I'm still on vacation...I should be able to read it this evening. I suspect it's the same low efficiency for the cat. converter.
I have heard that a cat. problem can result in over heating, because it restricts air flow.
Something still confounds me though: How could the cat. converter cause the fan to not come on until after the temp light comes on? I'm guessing the first thing should be to measure the water temp and see if it really is high enough to turn on the light. How high is that, anyway? Is it possible that the cooling fan/temp light issue is merely coincidental to the cat. problem, or could they be related, perhaps by the computer or something?
If the temp really is too high, then i have several potential problems
1. why the fan doesn't come on sooner
2. resolving the check engine light (cat. converter)
3. other cause of over heating (if other than fan not coming on sooner and the cat. converter).
Sorry for all the yacking...I just thought that since they could be related, I'd tell more of the story :-)
Ian
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Tom Greenleaf
Ultimate Carjunky
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Jul 21, 2010, 5:53 AM
Post #4 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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Ian: Do clean out the condenser and radiator of dust. Codes if running well and full power, running smoothly could have been triggered from the heat and may subside.
What doesn't add up it the fan not coming on as it's basically stupid and just sensing temp no matter why it reaches that temp.
Running heater is like adding radiator to the cooling system but you may (car designs vary) find requesting defrost or A/C and highest temp so it isn't working so hard will trigger fan to come on and be more effective. It seems lack of fan was the cause of overheat more than the other things if I'm understanding this so far.
When not overheating the converter may be able to handle the ordinary work load it gets and be ok - can't say for sure. Any situation that makes an engine run less than perfectly can tax the converter and even kill it. If full power now it may (probably) isn't clogged or a restriction but could be unable to do it's magic.
Again - I don't see the connection between sensor not putting fan on and any cat converter issue which may add to the heat but cooling system doesn't seem to be even trying,
T
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completelyhis
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Jul 26, 2010, 12:31 PM
Post #5 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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Tom,
I cleaned the condenser and radiator. It still over heats, though after clearing the code it hasn't come back....going on 100 miles.
I let it get hot enough for the hi-temp light to come on (I had to remove the cooling fan relay to get it to over heat while it was idling). I used an infared thermometer (the kind w/a laser) and tested the temp when the hi-temp warning light was on. It peaked at just over 200 degrees F. This makes me think that maybe the temperature sensor is giving a false reading to the hi-temp light on the dash.
I don't want to jump to that conclusion to quickly, though. The coolant was steaming, and I'm not 100% confident in my method of reading the coolant temp. This is a closed system, so the "radiator" cap is @ a union in the top radiator hose, not in the radiator itself.
The radiator fan switch (Wells part #SW2400) costs $105, while the coolant temperature sensor (Standard 5s1491) is only $16. So, if I was going to guess, I'd guess on the cheaper one first :-), esp. my hunch is compatible w/that.
So....what's your opinion of my hunch? Is it possible to test coolant temp. sensor? Is it an open/closed type of switch, or is it the type i'd test different voltages @ different temps?
Thanks,
Ian
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Tom Greenleaf
Ultimate Carjunky
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Jul 26, 2010, 6:27 PM
Post #6 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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Try hard not to let it get too hot even for testing.
General: Cooling fan switch is for the fans. Coolant Temp Switch is to tell the 'puter that engine is cold and deliver more fuel till warmed up - not involved in this IMO. Yet another makes the light go on.
$105 seems insane for a switch! In that you saw steam despite infrared temp sensing it probably is really getting hot. If that switch is in the radiator the radiator may be the fault?
A reason for late fan and the steam noticed could be that the pressure cap wherever located doesn't hold pressure and with most thermostats set to 195+/- that's close enough to make bubbles of boiling and the hot air bubbles both don't cool well and make sensing late. Hot liquid is faster than hot air on the sensors.
Gotta know this is full of coolant which is sometimes tricky. While cool try squeezing upper hose and look at recovery tank. If bubbles come up that's air of course and should be liquid or nothing by doing that.
For now I'm thinking switch or air. Air unfortunately could be combustion gasses from engine gaskets like head gasket but not wildly bad if air is the ongoing culprit.
It can run cool so I'm leaning towards a switch problem. Not sure how the action of it is. It may ground a wire at a certain temp triggering the relay to fan or be an in line temp sensitive on off switch.
More reason to blame switching instead of air is that heater works. If low or boiling they don't.
Pressure again: Each pound of pressure the pressure cap provides is worth ~3 degrees more temp F. before liquid coolant will boil - FYI. No pressure it is likely boiling as said,
T
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completelyhis
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Jul 26, 2010, 6:38 PM
Post #7 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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Tom,
Thanks for the reply. I should have clarified that i saw the steam with the cap off (Was doing it w/cap off to have access to water, to test water temp).
I have noticed a few things:
the upper hose sometimes seems to cave in on itself, like there's negative pressure sucking on it. this happened after my testing. I release the radiator cap, and the hose expanded, as air entered the system. I'm guessing air is bad. i'm also guessing that means the cap is holding pressure.
It seems that the resevoir is always above the full line, even after an amount of coolant has left the system (like when i was testing, and it was gurgling out for a bit.)
I wonder if the caved in hose and the resevoir that doesn't seem to drain back into the radiator are related to eachother, and possibly to the over heating problem?
also - what is the sensor that tells the hi-temp light to come on? Just in case the light is coming on erroniously.
That's all for now!
Ian
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Tom Greenleaf
Ultimate Carjunky
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Jul 26, 2010, 7:02 PM
Post #8 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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Strong clues with caving in hose! Cap does two things. It holds pressure of the coolant expanding and when it cools allows coolant from recovery tank back to rad and engine but from bottom of recovery tank so liquid only. If it's restricted in allowing return a hose could be under suction and never should be. If a hose collapses it could be the cause of late hot coolant reaching sensor. I tend to gravitate towards common denominators of one thing wrong causing more than one issue. At idle most hoses wont collapse. Some return hoses to water pump can suck themselves collapsed but usually with raised RPMs.
Cap probably should go for correct new one.
One more thing: If not already said, check coolant for freeze protection level. If stronger than 50/50 that doesn't transfer heat well. Still doesn't account for late fan though. If too strong lower it's percentage carefully and recheck when well mixed.
T
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completelyhis
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Jul 28, 2010, 5:40 AM
Post #9 of 13
(2735 views)
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Re: cooling fan doesn't turn on until hi-temp light
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Tom,
I replaced the rad cap, and that didn't fix it - coolant still wasn't getting from the reservoir to the engine. So I disconnected the supply hose and noticed it was not flowing from res. to cooling system. So I removed the reservoir and emptied it out, noticed a lot of sediment gunk @ the bottom. I cleaned it out, put it back together, filled it up, and.....PROBLEM SOLVED!
Thanks for all the help. You saved me from needlessly replacing expensive parts!
Ian
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 28, 2010, 6:14 AM
Post #10 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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Excellent Ian! No harm in a new radiator cap as they are crital to the system.
So glad you noticed and fixed blockage to recovery reservoir. That explains tons! Rare to happen and plug solid like that but it must work - you found it and just now hope no issues with running hot in the past arise,
T
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bobfrompgd
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Nov 17, 2010, 5:03 PM
Post #11 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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I have an old jeep with cooling problems. I did not like the fan coming on so late. I put a toggle switch on it so I control it. very much helped my cooling problem. Next thing is a heavy duty radiator. I try to be McGiver. I rarely go to mechanics. I have also found in this vehicle in summer it runs a bit cooler with just water in it.
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Tom Greenleaf
Ultimate Carjunky
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Nov 18, 2010, 2:25 AM
Post #13 of 13
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Re: cooling fan doesn't turn on until hi-temp light
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Ditto. It's now an old thread and never use just water. You really want more heat transfer use salt water but expect everything to rot out fast,
T
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