Changing the Coolant Temp Sensor (help)

[mechanism]

Hey everyone, I have a 1999 Falcon AU and I was just wondering how to change the coolant temperature sensor.

Can anyone tell me how hard it is? I have had a look and it looks pretty tight around the back of the engine near the firewall. Do i need to remove anything to get at it?

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Here is the problem I have been having and why I have decided to replace the sensor
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Driving on the freeway or revving much up around the 2000rpm causes my temp gauge to fly up above the 'normal' position (between the n and the o on the dash), this also causes the engine to go into a low and rough rpm (probably controlled by the computer to protect it from overheating). If i stop and let it idle, it cools down quite quickly and returns to the normal point. so i have to drive like a grandma and avoid freeways.

First I thought it might be the cooling system itself so i flushed it and changed the thermostat and the upper radiator hose (just cos i had a new one).

still the same problem.

Then I thought it was either the thermo fans, or the water pump. But on second thought, it wouldnt cool down quickly at idle if it were. (right?)

So i read a thread on here where someone describes almost exactly the same problem and it turned out to be the coolant temp sensor. So thats what I am going to try to replace.

any thoughts, tips or ideas as to the easiest way to do this or if you think it might be a different problem?

note: i'm not loosing coolant so its not that.

[Whoosha]

I would check the thermo fans first and make sure there coming on . With the engine off make sure they spin freely, then start and leave running with the A/C on and see if they switch on at all, if so then move on to the next check

[mechanism]

yeah the fans are running. about to try the sensor.

[5.0 ED]

Isn't there 2 coolant temp senders on AU 6cyl's, the one in the back of the head is for the engine overheat strategy, and the one in the front in the thermostat housing is for the actual temp gauge and main ECT sender?

I dont play with AU 6's so i could have it wrong, but i thought there was still the main front ECT sender, in which case i'd be replacing this one first.

[dieseltrain79]

Overheating under load usually means Radiator is blocked ...

I would look into replacing that 1st . Seeing as both fans are working and you have replaced thermostat .

I am having the exact same isue , and i am 99% certain it is the Radiator as it is the culprit for those symptoms ...

1% headgasket issue , but doubt it on AU plus .

[mechanism]

5.0whiteaughia - Nah, theres just one for the AU 6, on the back. It does both apparrently.

dieseltrain79 - I have flushed out the radiator and seems to be good flow, so I'm not sure about it being blocked (spent an hour flushing everything out it was madness)

BUT as of today, i think i might be very slowly loosing a small amount of coolant (or my mind - i cant see it anywhere on the ground or around the engine bay but it was down a little from a week ago)

[dieseltrain79]

Any stains on the top of the alternator ?Water pupms start leaking onto it and it dries and doesnt make the ground .

[mechanism]

OK guys, here is the solution. it was a combination of 2 things. and it should have been more obvious but it wasn't overheating quickly like you would expect it to when i tell you what it was.....

YES dieseltrain79 the radiator was blocked. I didn't realise you could still get a decent flow with that amount of crap in there!!! my mechanic even called me up excited to tell me he had never seen anything like it! hahahaha!!! he told me to come by and check it out. i did, it was actually heavy.... LOL

he asked if he shoudl do the water pump too, i said yes. why not, its probably got heaps in there as well that would only end up in the new radiator anyway.... when I went in to pick it up, he showed me that it has actually split into 2 peices, but because of the amount of crap in it, and the way it was on so tight, it wasn't leaking. haha

oh well, now i have pretty much got a whole new cooling system for $600 (total including the parts i bought and stuff). he did a great job, and also topped up my transmission fluid today for free cos it started playing up

[dieseltrain79]

You would think i was qualified aye ;)

Glad to see its fixed

Ive got to change the radiator in my wifes car in the next few weeks , same symptoms , not as bad or as fast as yours , but dont want to let it leave her on the side of the road .

Already done water pump and thermostat , as water pump was leaking , but now also need radiator .

Just need to decid which radiator to buy now .... SO many on the market its crazy !

[Bushbasher]

When I did the Fairlane I was told it was 90% blocked and still working. It was only climbing up hill in 45c heat that showed up the problem so I invested in a copper radiator. More importantly though, I also got a netting sock that slips into the top hose inlet and is held in place by the hose clamp that catches any left over crud that's still circulating in the cooling system so it doesn't wind up back in the new radiator blocking it again. Because sediment will sit in the bottom of the block you'll never get it all out while flushing and it'll only ever be on the move during a sustained high RPM run like a spirited highway or twistys blat so the sock is there to snag the crap when this happens. You should be able to get one from any decent radiator place like Natrad etc.

Bushbasher

[FG Brake]

How do I unclip, undo the 2 wires on the sensor. I can hardly reach it behind the head.
Can I short it out to check if fans come on?
My problem is I overheat at lights and steep hills. Both fans come on at start with A/C on. (thanks someone)