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Technical Temperature Gauge Weirdness

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Technical Temperature Gauge Weirdness

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IAFYM

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Hello, First off, I have absolutely no idea about cars so, I don't know what I'm talking about and am not sure if I actually have an issue or not.

I recently took my car for its MOT which passed fine but I've since noticed that the temperature gauge in the car binnacle thing gets to half-way between the quater way and half way mark and sits there for quite a while (sometimes it moves up a little bit and then will slowly move back down) and eventually, after what seems like much longer than before moves to the half-way mark and will sit there for a bit but will occasionally dip back down slowly and then move back up to the half way mark again (I hope that makes sense). It seems to do this moving around a fair bit (it doesnt dip down a lot) which I've never noticed before. I'm sure it used to, once up to temp sit right in the middle of the gauge.

Someone said to me that it might be the sensor that could be on its way out. About 2 years ago I had the who thermostat thinggy on the side of the engine replaced as the last one developed a leak. Someone said that a big car parts place sell something called a 'Coolant Sensor' which is what I need? rather than replacing the whole thermostat housing thing again as it might be the sensor that is not working reliably anymore? I have no idea what I'm talking about.

Any advice or help would be good.
 
IAFYM said:
Hello, First off, I have absolutely no idea about cars so, I don't know what I'm talking about and am not sure if I actually have an issue or not.

I recently took my car for its MOT which passed fine but I've since noticed that the temperature gauge in the car binnacle thing gets to half-way between the quater way and half way mark and sits there for quite a while (sometimes it moves up a little bit and then will slowly move back down) and eventually, after what seems like much longer than before moves to the half-way mark and will sit there for a bit but will occasionally dip back down slowly and then move back up to the half way mark again (I hope that makes sense). It seems to do this moving around a fair bit (it doesnt dip down a lot) which I've never noticed before. I'm sure it used to, once up to temp sit right in the middle of the gauge.

Someone said to me that it might be the sensor that could be on its way out. About 2 years ago I had the who thermostat thinggy on the side of the engine replaced as the last one developed a leak. Someone said that a big car parts place sell something called a 'Coolant Sensor' which is what I need? rather than replacing the whole thermostat housing thing again as it might be the sensor that is not working reliably anymore? I have no idea what I'm talking about.

Any advice or help would be good.
Click to expand...
Hey your problem is not the worst but it could be 'coolant temperature sensor' playing up. The best thing to do so you don't throw away money. Is to check yur coolant level is it at the 'max' or 'Kalt' mark on the coolant tank when the engine is COLD. Although you replaced your thermostat it could be playing up. But I would put it down to a coolant temp sensor
 
The thermostat will open/close the communication between engine and cooler to keep the engine at its optimal temperature.
If it stays open the liquid will keep circulating and the engine (coolant) temperature will fall if the car is moving fast enough.
If stuck half open, it might be not enough so the temp would rise to trigger the fan even if the car is moving.

Go for a run and once at normal temp stop the car (not the engine) on the side and see what happens with the temp; if it rises get the car moving again to (allow air-flow) cool it down...

This is how I'd check for a bad thermostat.

BRs, Bernie
 
Assuming coolant level is fine (and an appropriate mix, not just water!) it's either going to be the coolant temp sensor, or more likely the thermostat. Neither part is particularly expensive, or difficult to replace if you want to DIY.
 
Hi Everyone,

Thank you for all your help. I did what was suggested about letting my get up to temperature and then pulling over waiting and then driving off to see if there was a drop in the temperature and all I can really say is, no... There wasn't really a drop in temperature. To me, it doesn't seem like there is any rhyme or reason to why the temperature gauge drops.

I went onto the A3 and pulled over to the hard shoulder and waited for a bit (while the gauge was in the middle) and then pulled off up to 70ish mph and noticed no drop but about 5 or so mins later when I got to the next junction and started to come off the A3, I noticed a slight drop in the gauge. Other than that (and the random drops every once in a while when driving hme) I dunno.

Is it worth just replacing the whole thermostat again or should I take a chance on changing just the sensor?

Once again, thanks for the help and replies.
 
BTW you don't need to change "the whole thermostat", only internal part...

BR's, Bernie

If someone here helped You fix -or better- understand your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)
 
IAFYM said:
Hi Everyone,

Thank you for all your help. I did what was suggested about letting my get up to temperature and then pulling over waiting and then driving off to see if there was a drop in the temperature and all I can really say is, no... There wasn't really a drop in temperature. To me, it doesn't seem like there is any rhyme or reason to why the temperature gauge drops.

I went onto the A3 and pulled over to the hard shoulder and waited for a bit (while the gauge was in the middle) and then pulled off up to 70ish mph and noticed no drop but about 5 or so mins later when I got to the next junction and started to come off the A3, I noticed a slight drop in the gauge. Other than that (and the random drops every once in a while when driving hme) I dunno.

Is it worth just replacing the whole thermostat again or should I take a chance on changing just the sensor?

Once again, thanks for the help and replies.
Click to expand...


I would agree that the thermostat is most likely faulty. Sensor faults are more likely to be a complete failure or temperature indication jumping around, not the slow variations you are seeing.


Robert G8RPI.
 
Check the wiring:
1. to the sensor
2. the connector at the sensor in case it's dirty/loose
3. the engine earth

Just might be an electrical gremlin not a mechanical one
 
g8rpi said:
I would agree that the thermostat is most likely faulty. Sensor faults are more likely to be a complete failure or temperature indication jumping around, not the slow variations you are seeing.


Robert G8RPI.
Click to expand...

Ok, Is it a relatively easy thing to do, to DIY change the thermostat that is? It looks like its in a really awkward position. Like I say, I know nothing about cars... Would I need to drain the cooling system and when I refil it does it need bleeding?

DGPunto said:
Check the wiring:
1. to the sensor
2. the connector at the sensor in case it's dirty/loose
3. the engine earth

Just might be an electrical gremlin not a mechanical one
Click to expand...

It may sound stupid but how do I check the engine earth? A while ago, I did have an issue with the earth (it broke in half at the point it was mounted to the car body before it went to the gearbox) The solution the garage came up with was to leave the original bit from the battery and then put a new cable from the car body to the gearbox, this looks rather dirty and a little corroded now.

Should I unplug the wire from the sensor and clean it? Does it just pull backwards off the sensor or is there a clip or something?

Once again everyone, thanks for all your replies.
 
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