Cooling issue

Nippon

Nippon

Member +
Hey guys

Got a small issue with my cooling.

My radiator fan didnt come on once and the car overheated. Even though the temp gauge was reading normal (halfway between hot and cold)
I assumed the water temp sensor was faulty.

So i rigged my fan direct to the battery on a mannual switch so I could turn it on and off as I wanted untill I got a new water temp sensor.

So anyway... got a new watertemp sensor.

Problem remains.
Fan not coming on automatically, temp gauge reading normal yet sill overheating.

Thermostat is working cos both top and bottom rad hoses are the same temp.
Raditor has been throughly bled and no air locks in there.
In car heating all works fine.

Any ideas?

Matt D

EDIT: Forgot to add: when driving say on the motorway and air is coming through the front the water temp needle stsays at 0. Only moves up to halfway when sat still.
I have a Sard low temp thermo. (68degrees)
 
Last edited:
dac69er

dac69er

Super Moderator
Sounds like the thermostat is no good. Why do you say its overheating is it boiling up or something?
 
Nippon

Nippon

Member +
Yeah. Boiled over. Full expansion bottle, steam, bubbles the lot.

Dont think its the thermostat. Its something electrical. Thats why the water temp gauge doesnt show that its too hot and the rad fan doesnt come on.

Is the raditor fan controlled by the gauge or something else?
I've replaced the water temp sensor so why isnt my water temp gauge showing that the water is too hot?
 
dac69er

dac69er

Super Moderator
which sensor did you actually change?

the 2 pin green plug one is the water temp sensor for the ecu. one of the single wire sensors is for the gauge, think its the bigger of the 2 but cant remember. then the single wire round white plug one at the back of the thermostat housing controls the rad fan. disconnect it and see if the fan runs or not.

if the gauge is reading cooler when you drive along and then goes back up when you stop then it does sound like the thermostat could be playing up, but wont explain why the rad fan isnt coming on. how old is the thermostat? did you buy it new?
 
weeJohn

weeJohn

Lifer
Is the water pump pumping the coolant? Check the belt is good and the heaters inside are getting hot.
 
Nippon

Nippon

Member +
dac69er said:
which sensor did you actually change?

the 2 pin green plug one is the water temp sensor for the ecu. one of the single wire sensors is for the gauge, think its the bigger of the 2 but cant remember. then the single wire round white plug one at the back of the thermostat housing controls the rad fan. disconnect it and see if the fan runs or not.

if the gauge is reading cooler when you drive along and then goes back up when you stop then it does sound like the thermostat could be playing up, but wont explain why the rad fan isnt coming on. how old is the thermostat? did you buy it new?
Click to expand...

Yeah thermostat was brand new when i bought it. Been in a couple of years.
Shouldnt have failed already surely???

I changed the 2 pin green plug sensor thats hidden under the dizzy cap.
I'll try disconnecting the sensor u mentioned and see if the fan comes on.
 
weeJohn

weeJohn

Lifer
Nothing electrical should make it boil over under normal driving, even if the fan is not coming on, when driving, air goes through the rad to keep it cool. Only after sitting in traffic for a long time if the fan doesnt come on, then it will overheat. The stock temp sensor only shows above the middle of the gauge when coolant temp is over 110 degrees, when its in the red the coolant is already boiling.

I think your head gasket has gone to be honest.
 
Nippon

Nippon

Member +
I doesnt boil over when driving. Sorry if ive confused the thread.
Its fine when driving.
It boiled when I was testing to see if the rad fan would come on automatically.
Sitting still on fast idle.
Fan didnt come on, temp gauge reading halfway yet rad boiled over.

Its an electrical issue related to the water temp gauge and the rad fan which is my problem.
 
dac69er

dac69er

Super Moderator
As with anything, they can fail very quickly, and sometimes they don't. The water temp gauge and the fan control switch are 2 entirely different circuits. The green 2 plug sensor has no affect on either, it is only to tell the ecu what the coolant temp is. If that fails it causes bad running and/or poor fuel consumption.

Have you tried uplugging that sensor yet?
 
weeJohn

weeJohn

Lifer
If its a GT, pulling the plug off the fan switch (faces towards the bulkhead on the thermo housing) should energise the relay, a Glanza needs the plug to be shorted to earth. Do this to check the relay is energising in the engine bay fuse box, if so, checking for power at the fan plug is the next step.

Is it just pushing water out the open rad cap spout or is it pushing loads of hot water/steam into the expansion bottle?
 
Nippon

Nippon

Member +
dac69er said:
As with anything, they can fail very quickly, and sometimes they don't. The water temp gauge and the fan control switch are 2 entirely different circuits. The green 2 plug sensor has no affect on either, it is only to tell the ecu what the coolant temp is. If that fails it causes bad running and/or poor fuel consumption.

Have you tried uplugging that sensor yet?
Click to expand...

Ok. Thats why changing the water temp sensor has done nothing then.

No havent tried the other sensor yet. On my list for tomorrow.
 
Nippon

Nippon

Member +
weeJohn said:
If its a GT, pulling the plug off the fan switch (faces towards the bulkhead on the thermo housing) should energise the relay, a Glanza needs the plug to be shorted to earth. Do this to check the relay is energising in the engine bay fuse box, if so, checking for power at the fan plug is the next step.

Is it just pushing water out the open rad cap spout or is it pushing loads of hot water/steam into the expansion bottle?
Click to expand...

Ok. Ive got a Glanza so I'll do this tomorrow.
Rad cap was on. It pushed hot water/steam into expansion bottle.
 
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