bleeding problems

[phil 1]

Hi,
I have drained and flushed the cooling system and changed the water pump and coolant temp sensor today.
I have refilled the cooling system same as I always do and started the bleeding process. I have never had any problems using Mazda’s recommended bleeding process and all was going well until the engine temp got up to normal the gauge is modified with a masons alarm so unsure what the actual water temp is. As the engine temp started to rise just over normal the cooling fans kick in and run constantly and bring the engine temp back down so I cannot get the thermostat to open or the bottom hose hot!.
I’m guessing the only thing I have changed that would affect the temperature the fans kick in is the new sensor. The sensor I have fitted is a blue print ADT37220 http://www.blue-print.com/newweb/index6_fs.asp?i=0
Has anyone fitted one with success? I have let it cool down and started the proses 3 times and the same thing happens I have tried the seesaw method to see if that worked but still the same thing happens.
I have given up for today and will try again tomorrow so if anyone has any suggestions on what to try next I would be most grateful.
Thanks phil

[Northern Bongolow]

if the sensor is for a bongo which i presume it is it will have a preset resistance which should change with temp, you could take out the sensor and check its values cold and hot. its in the bongo manual what the resistance readings should be.

ive found that the copy sensors are not as reliable as the gen but some may argue that one. check to see if the sensor plastic piece is wobbling on the brass probe bit, if it is i could be altering the resistance of the sensor so triggering at the wrong temp. or the 2 pin connector is not good.

or more likely its reading the true temp in the head so may still need bleeding, is there coolant in the top hose from the head to the rad, give it plenty of squeezes to help shift any trapped air.

[teenmal]

Phil, if you want to override the ECT sensor for bleeding purposes, remove the connector from the ECT sensor ( without removing the sensor)and fit it to your old sensor. This should stop the fans from coming on and enable the THERMOSTAT to open.

Once you get the thermostat open you can go back to the New ECT sensor and check the values, you should be able to do this without removing the sensor. If values ok just reconnect the wiring to the new ECT.

Any doubt remove and replace Thermostat.

[phil 1]

Sorry for the late response.
So Sunday i tryed to bleed it again managed to get the thermostat to open briefly but the fans kicked in straight away so still not right . Anyway gave up as i broke the old sensor removing it i couldn't try plugging it back in and not sure how to test the sensor so decided to order a genuine sensor. Fitted it last night bleed the system and all is well bongo is behaving as it was before so all i can assume is it was a doggie sensor. Lesson learnt buy genuine parts where possible
Thanks for your input guys much appreciated

[cmm303]

Do fans normally come on during bleeding?

Mine don't (new Mazda stat, copy sensor from AVA)
Mate's did a bit but not enough to prevent stat opening and bleeding.

[phil 1]

Do fans normally come on during bleeding?

Mine don't (new Mazda stat, copy sensor from AVA)
Mate's did a bit but not enough to prevent stat opening and bleeding.

That depends on how long you let the engine run after the stat opens.
The fans should not operate before the stat opens that was the problem with the blue print sensor fitted the fans were operating before the stat opened.
I always bleed mine using the mazda recommend bleed method and never had any problems and that involves running the engine for some time after the stat opens so the fans come on and run for a minute or so.
I use this method manly because i find the see saw method hard to do on my own. With the genuine sensor fitted everything happened as before i changed the sensor.
Hope that makes sense

[cmm303]

Do fans normally come on during bleeding?

Mine don't (new Mazda stat, copy sensor from AVA)
Mate's did a bit but not enough to prevent stat opening and bleeding.

That depends on how long you let the engine run after the stat opens.
The fans should not operate before the stat opens that was the problem with the blue print sensor fitted the fans were operating before the stat opened.
I always bleed mine using the mazda recommend bleed method and never had any problems and that involves running the engine for some time after the stat opens so the fans come on and run for a minute or so.
I use this method manly because i find the see saw method hard to do on my own. With the genuine sensor fitted everything happened as before i changed the sensor.
Hope that makes sense

thanks