Overheating Rant

[CLuTZ]

I was driving my EVO today, as I do everyday, when I hear a whistling noise over the top of my ABC talk back radio....

I turn the radio off and there's a whistling noise alright- I look down and the temp gauge is on 3/4! I quickly pulled over, slammed the fans on fast and hot, and pulled the bonnet to see what the hell the deal was.

The water in the overflow was boiling, and it spewed most of the water out the overflow, causing it to overheat. I was in Roxburgh park working, and managed to get some water into her and limp down to CREATD, where we bled the air out of the coolant system properly- it wasn't leaking from anywhere and there was no bubbles, or water in the oil. Good sign. We then noticed that the radiator fan wasn't coming on when it was supposed to, causing it to start overheating whilst stationary on idle.

I then hardwired the fan to the battery, and the fan was working fine, but when I put everything back together, the fan wouldnt come on by itself. I unplugged the coolant temp sensor which made the fan run constantly, but threw a CEL which was good enough to get me home.

Once home I swapped thermostats and coolant temp sensors off my RVR (best thing that car has done in a while :lol and fired it up- no overheating on idle. Went for a boost- no overheating. Returned home- idled for a bit, and the fan came on by itself. Happy for now.

Thats my rant. I'm just hoping I havent done the headgasket- would be pretty gutted considering its only 5000km's old.

What I really want to know is- cant the ECU tell that the coolant temp sensor is showing the wrong reading, causing it to not switch the fans on- then throw a CEL? I would have thought that a CEL would have appeared when it failed, then switched the fans on constantly (like when I took the sensor plug off)??




dre

 

[Richard]

Not on these old cars Dre, even new cars have there moments with running like a sack of shit and it not detetcting the problem by itself.
I had a great one the otherday, GT libertys injectors are known to block up and cause a rough idle, ok cleaned injectors in no change, car is reving fine but idle is all over the shop, stalling etc but no check engine light at all, the problem was found to be that a filter in the oil line to the VVT hub had fallen apart causing the RH bank to be running ~50psi advance or some crap all the time. The evidence was in the data veiwable as a sensor reading on the diagnostic computer but it internally was unable to detect the problem.

 

[JAP63]

Dont appear to be linked do they....have you looked into why the thermo never turned on? Whatever the link is between the coolant temp reading and thermo switch engagement must be up shit. Just the coolant temp sensor??

Theyre a funny thing, just like when the thing fail and reads cold all the time and the car runs that rich it gets 150k out of a tank of fuel

 

[CLuTZ]

Well being an EVO, they don't have the sensor in the bottom of the radiator, unlike GSR's, so does that mean the ECU tells the fans to switch on, by the coolant temp sensor coming up to the right temp?

 

[BYBY5L]

good to see its fixed man, h/g should be fine, ive driven mine with split radiator hoses an its still sweet, a big hmmm with the ecu an sensors tho

 

[lozza]

my understanding is that the engine temp sensor is separate to the temp indicator on the dash.

the engine temp sensor, being a type of thermistor (temp variable resistor) which outputs to the ECU linearly (hopefully) with temp change. this would correlate with a certain "temp." set in the ECU, say 92 on 88 off. The fan uses this signal to turn on and off as necessary. The temp dial on the dash would then have no bearing on this.

so either there is a problem with the input from the thermistor to the ECU or the output to the fan.

that's my basic understanding?

 

[CLuTZ]

my understanding is that the engine temp sensor is separate to the temp indicator on the dash.

the engine temp sensor, being a type of thermistor (temp variable resistor) which outputs to the ECU linearly (hopefully) with temp change. this would correlate with a certain "temp." set in the ECU, say 92 on 88 off. The fan uses this signal to turn on and off as necessary. The temp dial on the dash would then have no bearing on this.

so either there is a problem with the input from the thermistor to the ECU or the output to the fan.

that's my basic understanding?

Yeah that's how I thought it worked too. What I can't figure out is why the sensor failed, but didn't throw a CEL. Lets hope it was the sensor. If she overheats again today, then i'd say the headgasket is kaput.

 

[WindeX]

Same thing happened to me on my Jeep the other day, it turned out that it was one of the connectors to the fan that wasnt quite connected and cause it to not turn on. The Jeep has a crank fan so it was all fine until I went 4wding in the damn thing then it got a little toasty mid hill climb and I had to cut the trip short.

 

[CLuTZ]

Right-o, did about 120 kms so far today, and all is well again.

I had a good look at the thermostat I pulled out and it looked perished, and due for replacement.....

Doesn't explain the fans not switching on though- faulty sensor AND bad thermostat?

 

[WindeX]

Good to hear, nothing worse than overheating! A pet hate of mine :S

 

[blackers10]

I would say the switch dieing just made the thermostat problem more obvious...

 

[Dean]

When I had my overheating problems I thought I may have done a head gasket too, yet all turned out fine.
Genuine gaskets are the shit :thumbsup: