Technical Now WHAT!!! OVERHEATING?

[TheCROW]

Hey guys does anyone know the make and model No. of the coolant temp sensor? I have a Bosch store near my office and I was thinking maybe I'd go buy one so I can replace it tomorrow
My car is a 100SX 99 Brava 1.6 petrol manual. (mk2).

Just had a thought: What's Water Temerature Gauge? Could it have something to do with my problem?
Thanks.

 

[TheCROW]

Just got back from the FIAT dealership, bought the coolant temp sensor for about 22 euros...
The odd thing is that today morning I sat in traffic and had AC on and the temp remained in the center... Weird, I'm beginning to be positive that this is releated to electrics...

What about the Water Temerature Gauge? Exactly what does it do and could it have something to do with my problem?

Thankyou all... I have a feeling this will be one of the longest threads around...

 

[jug]

the water temperature gauge is the thing you look at everyday when you watch the temperature. you worry about it going up more than half way.

they are commonly faulty, but when they stop working correctly then tend to jump all over the place or stick at min or max, not occasionally show a slightly higher temperature.

 

[TheCROW]

Thanxalot Jug, I'll post back as soon as I change the sensor, hopefully tomorrow

 

[BLONDEBLOKE]

Phew - long thread!
Just to throw my twopence worth in, i'm an engineer who has designed a few cooling systems in the past, although nothing for cars with less than 450bhp!.
start with simple mechanical tests:
with car stationary and engine cold, start the engine, watch the temp gauge and at some point as it climbs it should drop back down a little - this means the thermostat has just opened. Now go and check the coolant hoses to the radiator - you should be able to feel them getting hot as the hot water flows through the rad.
If water is flowing then this tells you that thermostat is ok and water pump is ok.
if temp gauge never drops and rad hoses don't get hot then 2 causes - thermostat faulty and stuck closed or water pump faulty. swap thermostat or remove it and drop it in a big pan of hot water and check the wax valve inside moves as it heats up (should be a spring loaded valve visible inside it). Do this first because to change the water pump is generally a cam belt change at the same time.
If temp guage never drops but rad hoses do get hot then suspect a faulty thermo stuck open it will just take longer to heat up - you should be able to feel hot water through the rad hoses after a longer wait. This is not a disaster - just takes long time to heat up esp in winter.
as temp gets over half way on gauge (usually 90+degrees) then you should feel + hear the rad fan kick in. If not and the temp gauge gets to 3 quarters upwards then suspect faulty fan, fuse, control unit or temp sensor (or maybe dash connection).
check fan by running with 12v source. Check fuse with multimeter/sight. check temp sensor with multimeter / swap new one.. Check control unit by swapping or diagnostic.
make sure all hoses and rad are bled and levels topped up and cap is not venting before you do this!
and don't burn your fingers when you bleed it cos it bl00dy hurts!
just make a list of checks and work your way through them systematically - should indentify if its electrical or mechanical, then if you do go to a garage you can tell them and they should be able to fix it quicker and cheaper

 

[TheCROW]

Thanks BLONDEBLOKE for taking the time to reply,
I have checked all this and the problem is not solved.
The weird thing is that this doesn't happen all the time, it's intermittent and these problems are the darnest..
Just today I replaced the sensor and went to work.
I was stuck in heavy traffic and it was bloody hot outside. So I turned on the aircon. After some time stuck in traffic, slowly moving and stopping, the temp gauge went up to the dot just after the center dot and it remained there for the rest of the journey. As soon as I parked the car and turned off the aircon, the gauge needle went down slowly back to the middle.

The mechanic told me that the fan should have 2 speeds,low and high. He suspects that my fan is only operating on low speed. He said that as soon as I turn on the aircon, the fan should turn at a higher speed which is not happening.
Does anyone know if this is true? Is the fan supposed to work at high speed when the aircon is on? If this is the case, I suspect mine is only operating at low speed. How can I test this?
Thanxall for helping me through this ordeal

 

[jug]

oh you have air con!!! there's a relay to operate fan speed, the connection onto it often gets rusty. check that. theres a few more threads about this exact problem in the marea section.