With the further description, I'd also chime in on the fan switch being bad. A proper working fan switch keeps the temperature in the radiator -- and subsequently the rest of the engine -- from fluctuating. The ECT (Engine Coolant Temperature) sensor, which is the two-wire connector you circled, tells the ECU how to manipulate the air, fuel and timing. The ECU doesn't actually moderate the temperatures in the engine. That duty is left up to the thermostat which determines whether coolant needs to flow, and the radiator fan switch which determines if additional cooling is required.

Simply disconnecting the water temperature switch, which comes off the fan and is mounted on the bottom of the radiator, should cause your fans to run -- it's a safety measure, since the thermostat can keep the engine warm even if the radiator is below 83C. The water temperature switch should cause the fans to start running at 93C. To inspect the switch you'll have to remove it, which once you disconnect it is simply a matter of unscrewing it -- though you will leak coolant as a result so I'd do it when the engine is cold, and find something to temporarily plug the hole.

The water temperature switch can be inspected in the same manner as the other coolant temperature sensors, with a multi-meter and a pot of water on the stove. A key to properly testing these sensors is that they cannot be sitting on the bottom of the pot, since the pot's bottom will be a different temperature that the water. There should be continuity between the connector's terminals below 83C, and no continuity above 93C. If otherwise, replace it.

You should perform a leakdown test. Possibly could have a blown head gasket.

^ I did not read the whole thread but it seems like everyone has mentioned the most common problems, if all else, then check the head gasket. Is your oil milky? or is your radiator coolant not looking like it? IDK, i just read pieces of the thread.

im surprised no one has asked yet but when was the last time you replaced your pressure cap i recommend 30k some people say 3 years if the cap isn't holding pressure thats why you are overheating even if it is fluctuating it could be caused by that i had the same problem i took the cap off of my integra and put it onto my celi and it solved my problem so give it a try another thing when was the last time you replaced your water pump you may have corrosion in the pump if you are using the toyota factory red coolant it has a solidfying agent in it to help detect leaks. just a thought good luck man.

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X2 Time for a water pump. You need to know that is good before you spend a lot of time on fans ect. Even if it isn't toast yet it could br underperfoming.

The water pump either leaks and makes a bunch of screeching noise or it operates 100% normally. If it isnt leaking out of the weep hole then dont replace it. Its two solid hunks of metal with a bearing at the center.

i didnt think of that, that could be it, its always the smallest thing, it does make a lot of sense, tho, if your temp is going down and up so easily and the fans are kicking on, i would have changed the cap when you changed your thermostat, and your anti-freeze

This post has been edited by zfjohnson07: May 28, 2012 - 8:58 PM

I don't think most of you guys are reading the thread before posting but I already had replaced my Radiator cap and the previous owner recently changed the water pump and he even left me with the receipt. I never thought or heard of the fan switch. I'll think I'll have to give that a try tomorrow.

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Yea. It's like how you said it. And I meant when I heard the fan kick on when I came to a red light. My car only has a short ram so it's not a loud car. And lemme rephrase it. The fan turns off once it hits about 50%. I never really thought about it but my temp gauge actually goes up to the operating temperature pretty quick. For a fact much quicker than before I encountered the over heating problem. It takes roughly 3 min to get to operating temperature when before it takes about 6 mins? I don't know if that had to do with anything but I just found that not really normal?

couldnt tell if its been asked or answered yet but is it blowing out water from the radiator into the overflow bottle?


by the way, instead of rewiring the radiator fans to run them full time you simply unplug the thermo-switch in the bottom, just leaving it hangin there the ecu will run the fans will full time.

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Yea it's blowing out water to the overflow bottle. That should mean there's good pressure. Right?

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Is your Intake Air Temperature sensor plugged into your air intake, after the filter?

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No. That means the cap is seeing enough pressure that its valve is opening to allow water out. If the cap is an incorrect rating, isn't on properly, or is not functioning correctly, then the pressure in the system and subsequently the temperature will be incorrect as well.

There's some simple tests for the temperature gauge. Disconnect the sensor (on the water neck, single-wire sensor) and ensure that the gauge reads cool. Ground the connector through a 3.4W test bulb and turn the ignition to ON; the gauge needle should move towards HOT. The gauge may also be checked at the cluster, for resistance. Unfortunately, I don't have access to the sixth-gen's BGB so I can't tell you which terminals on the back of the cluster are involved in testing.

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I'm going to have to keep that in mind. I just finished troubleshooting my car earlier. But I'll do this test tomorrow.

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Which sensor is that? Is that the one that looks like a probe that's inserted into the intake piping?

So today I decided to replace my lower radiator hose because I noticed it was leaking a bit at the water outlet. When I went to remove the hose the water outlet actually broke off. It was worn out and old. Since it was plastic, it was reasonable to why it would be like that. I went to AutoZone and replaced it with a cast iron water outlet.

What I did today was replaced the lower radiator hose, replaced the water outlet, flushed the cooling system AGAIN, and bled it AGAIN. Took it for a run and it had no progress. It was still jumping. -_-'


^This picture. You can actually see a piece of the water outlet stuck inside the hose^







This post has been edited by ILoveMySilly97: May 29, 2012 - 10:52 PM

same problem no fix

Well. I just installed a new radiator fan switch and no progress. I already ordered a Spectrum Premium radiator off of Amazon. Should be coming in sometime in 3-5 days. If this doesn't fix it.....then I'll just hope it's not a blown head gasket. I have no obvious signs of a bad head gasket YET at least. No milky oil or coolant.

yea same here n i just put in a new rad.

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Damn. Now that I think about it. I could've spent all that money I spent to replace working parts to a shop that could've done a diagnostic check on it. -_-'

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^^^This single post above should have its own sticky

This is why components should be tested prior to replacement.

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A pice of that old platic tube is probably blocking youtr thermostat openings mabey recheck the thermostat.

In your other thread on this issue -- you really should keep it to one thread -- you mention you installed a 170 thermostat. If you mean you installed a thermostat calibrated for 170 Farenheit, you put in the wrong thermostat. The 5SFE is designed to work with an 82C/180F thermostat. That you're not using a Toyota thermostat makes me also wonder if what you installed includes a jiggle valve and a proper gasket.

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Isn't it the lower the better? The degrees is only determines when the thermostat opens correct? So it wouldn't hurt to open a just a lil bit earlier. I mean it keeps the engine cooler. Or am I wrong?

I've just been through the same thing as you, No milky coffee oil/coolant etc. first the pipes corroded, then it overheated, tried flushes, trd stats, trd caps,... yep turns out block & head surfaces were way warped, gasket was leaking inbetween layers, it was just combustion pushing water out, there was no oil to coolant leak.

sorry pal, the more u drive it the worse its gonna get. rebuild it or get another motor now.

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No, the engine is designed to work at a certain temperature range. If colder were better, Toyota could have skipped using a thermostat entirely to keep the engine near freezing when driving. Air-fuel ratios are adjusted based upon engine temperature. It's the same reason those chips which fool the ECU into thinking the air is colder are a bad idea.

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Yea. I'm going to get my car diagnosed if replacing the radiator doesn't fix it.

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So I should just go back and buy the 180 one instead. Might try to return the one I just bought since I still have the receipt.

Ok. So here's an UPDATE. So. I let my car idle and heat up to about 70% and I just let it idle. It kept jumping when the fan turns on and off so I decided to unplug the sensor/switch so that the fan will always be on. When I did that trick. The gauge went down to about 45% and stayed there and never climbed or jump?

When it's connected. The fan will turn on for about 2-5 seconds max. I know that's too short. I think that's why I'm getting these problems. My fan is just not turning and staying on for the right amount of time. What I did was replaced the radiator and the fan switch. So I don't know why the fan isn't staying on for the right amount of time? Any ideas?

This post has been edited by ILoveMySilly97: Jun 11, 2012 - 12:05 AM

Same idea as has been advanced before -- test the fan temperature switch. Also, test the fan itself.

4. INSPECT COOLING FAN
(a) Connect battery and ammeter to the cooling fan connector.
(b) Check that the cooling fan rotates smoothly, and check the reading on the ammeter.
Standard amperage:
4A–FE and 5S–FE 5.8 – 7.4 A

A $10 multimeter saves a lot of money by preventing the needless replacement of working parts.

You haven't mentioned getting your timing corrected. If that's the cause of overheating, all this other work won't fix the problem.

This post has been edited by Galcobar: Jun 11, 2012 - 5:13 AM

Cooler is not necessarily better. This thread is getting clogged with garbage (including this one). If the fan stops running, give it a spin and see if it runs on its own for another 3sec. If it stops, its fan time. Also that nonuniform thermostat could be throwing a wrench into the system. If that fails, check back in. We'll get this thing worked out!