Fluctuating water temp gauge

[Kiwi_Jeeper]

Hey guys i have a problem with my temp gauge fluctuating while driving. its ok while i sit and idle it just sits around mid 90's bit once i start moving it starts to fluctuate up and down dropping to the first mark which is maybe around 60c? then rise back up to 100 then drop again..I've replaced thermostat temp gauge sender radiator and bleed it i don't know how many times and still not solved it :confused:...its got me stump any idea's on this would be much appreciated.

[Billnick]

Try blocking off 1/4 of the rad with a piece of metal sheet or cardboard. I think you are getting too much cooling. I had the same prob. It doesn't do it now I have an oil cooler fitted.

[Kiwi_Jeeper]

choice mate, didnt think of that.. im still running factory trans cooler so doesnt take up much space..i'll try your idea and let you know how i go.

Cheers Ben

[Windex]

Did you replace the front temp sensor or the one on the back of the head?

[quints]

You sure it's not just evidence of your thermostat 'cycling'? I see my guage do pretty much that -- particularly in winter -- when I'm highway cruising. I just put it down to the thermostat cycling. Tells me the water pump / fan clutch / radiator / thermostat . . . the whole 'cooling system' in fact, is working as intended.

[Kiwi_Jeeper]

I replaced the one at the back of the head which is def the temp gauge sensor i unplugged it to check i had no reading on the dash before i replaced it

[Kiwi_Jeeper]

quints- it may be? but that seems like a rather big drop in temperature and surely cant be good for a hot motor to be getting hold then cold like that

[Deezelweazel]

Fluctuations? Check your engine ground connections. Loosen them, apply a sprizz of WD40, then retighten them. Should solve your problem.

[Kiwi_Jeeper]

cheers for that weazel i'll give that a go but i think it is over cooling as putting a piece of tin in front of the radiator has helped just tinkering with the amount to find the right balance to get it hot and not too hot.

[janddbone]

Probably running a cold thermostat...

[Rosie]

Make sure you actually have the right themostat listed, Repco/Supercheap/Auto-One etc actually have the wrong one listed which is too cool.

[Billnick]

Probably running a cold thermostat...

Actually it's the other way around. We have a hot thermostat and the system can't produce enough heat to keep it open.

[kyphonii]

Mine was doing the same thing. With the air con on the temp would stabilise.
I replaced the Hoses, pump, thermostat + housing and a new belt, I solved the issue but not shaw which of the parts fixed the issue. I was intending to reconditioning the cooling system for the next few years.

Edit: The temp would stabilise at 100 (AC on) but never over heat, and after the new bits the temp runs half way between left mark and 100' so maybe I had an issue with the pump and possibly the thermo stat.
The temp still never goes over 100 and this is the hot end of Australia.

Edit 2: I also run and overly enthusiastic fan. The hub appears to by nearly locked at low temp, All you hear is the fan noise over engine noise, I will be replacing it with a new hub soon.

[Kiwi_Jeeper]

Hey fulla's just a quick update i put a cooler opening tstat in today and it has helped a little as it is not getting as hot therefore not dropping so much when it cools down so ill run this for a bit for now..I may go back to the hotter thermostat and add more tin in front of the radiator but not sure if it's worth it.

[Windex]

How did you change the sensor at the back? My temp gauge is now reading zero even after a drive. Tried to get the current one loose and it seems pretty tricky to free it up.

[junglejuice]

It is a major fiddle to remove that rear sensor....

[Windex]

It is a major fiddle to remove that rear sensor....

It sure is, the other sensor (up the front near the thermo housing) seems to be the one that drives the ECU and triggers the AUX fan. I had the rear sensor disconnected all weekend and the fan would still trigger after sitting still for sometime. Noticed that my fan clutch was not working as expected though, car hasnt had any overheating issues, but I can spin the fan when the car is hot with little to no resistance.

[rainman]

the back sensor is for for the dash display gauge only on pre-updates.

[Windex]

Replaced the sensor last night and it seems to have all sealed up properly. It has confirmed what I have suspected for awhile, my car is running a little hot. It sits just above the 100 mark most of the time but must be cool enough so as to prevent the aux fan from kicking in. I believe that my fan clutch is acting up but have not been able to confirm... time for a cooling health check!

[dazza96]

in my 96 obd 2 temp guage was allways 2 mm of the red before the fan kicked in changed both sensors one in back of head and one in thermostate houseing and it never made a diferance at all still the same so go figure so i now treat this guage as more as a ruff guide then set in stone cheers daz

[Windex]

Yeah I think I will let it settle in so I get a feel for the 'normal' range, I am not loosing coolant and not boiling it, I just want to make sure that my clutch fan is working as it should then I can be happy for the moment :D