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Temp Gauge

Rose35

Hi all,

Just a quick question on something I noticed yesterday eve about temp gauge in car (vw golf 08 1.4 petrol) driving home it was about 1 degree celsius outside, anyway, turned on heat blower to number 3 and heat was about right felt normal anyway but there was a slight and I mean slight adjustment in temp gauge from 90 degrees to maybe 89 degrees while blower was on, turn blower off and returned to normal. I never noticed this before, would ye think this is normal?

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Alanstrainor

It could be the thermostat sticking open slightly.

C4Kid

I had mk4 1.4 and a 1.6 mk5 - Both did the same thing in cold weather.

When you think about it the heat for the blower is coming from the coolant. You are essentially using an extra little radiator to bring heat into the cabin. This applys additional cooling to the coolant which is only amplified to the point you see it on the gauge in colder conditions.

If you go down a steep hill in cold conditions the coolant temp needle will drop slightly in a similar way.

Rose35

Alanstrainor wrote: »

It could be the thermostat sticking open slightly.

I thought it might be something to do with temp outside being cold because it returned to normal when blower was turned down or to off, but then again I have never seen it do this before

CiniO

In properly working cooling system, coolant temp gauge shouldn't really go down even at minus 30 deg.
On the other hand, if OP says it's only one degree, I wouldn't worry.

Alanstrainor

CiniO wrote: »

In properly working cooling system, coolant temp gauge shouldn't really go down even at minus 30 deg.
On the other hand, if OP says it's only one degree, I wouldn't worry.

Yeah, I'd keep an eye on it, probably fine. But the temp shouldn't change once it's warm.

Moanin

I've a similar scenario on a 2010 A4 TDI. The temp gauge normally is at 90 when the car warms up but lately I've noticed the gauge will drop to 70 or 80 and then back to 90. This happens on both long and short trips so I'm wondering if it's the temp sender or stat?

Rose35

Moanin wrote: »

I've a similar scenario on a 2010 A4 TDI. The temp gauge normally is at 90 when the car warms up but lately I've noticed the gauge will drop to 70 or 80 and then back to 90. This happens on both long and short trips so I'm wondering if it's the temp sender or stat?

This is only happening to me when I have the heat to the highest (27) and using the fan blower to the max (number 4) , so far anyway.........

Alanstrainor

Such running cold issues are generally related to the thermostat. Best get hem checked out.

Rose35

UPDATE...... I just rang my mechanic and he said what is happening to temp gauge when heater is on full is normal especially with these low outside temps we are having at present.
C4KID poster above explained it what with the golf having an extra radiator to bring heat into the cabin, having a service next week so will update if he finds anything related but for now it appears to be normal.

Alanstrainor

Rose35 wrote: »

UPDATE...... I just rang my mechanic and he said what is happening to temp gauge when heater is on full is normal especially with these low outside temps we are having at present.
C4KID poster above explained it what with the golf having an extra radiator to bring heat into the cabin, having a service next week so will update if he finds anything related but for now it appears to be normal.

I would have to disagree, there is something wrong, however it is not overly critical at the moment(my car is driving in the same weather, (and far colder without such issues). I would ask specifically to get the thermostat checked at the next service.

As a matter of fact, I had a Polo with the exact same 1.4 back in 2010 in the big snow, when it was well below freezine, and did not experience this.

Rose35

Alanstrainor wrote: »

I would have to disagree, there is something wrong, however it is not overly critical at the moment(my car is driving in the same weather, (and far colder without such issues). I would ask specifically to get the thermostat checked at the next service.

As a matter of fact, I had a Polo with the exact same 1.4 back in 2010 in the big snow, when it was well below freezine, and did not experience this.

I haven't noticed it before but then again I wouldn't normally have used the heat that high even though I have it since feb 2012, returns to normal immediately if i turn blower down a notch made me think it was def related to the heat output into cabin, what are you driving at present?

John T Carroll

Rose35 wrote: »

Hi all,

Just a quick question on something I noticed yesterday eve about temp gauge in car (vw golf 08 1.4 petrol) driving home it was about 1 degree celsius outside, anyway, turned on heat blower to number 3 and heat was about right felt normal anyway but there was a slight and I mean slight adjustment in temp gauge from 90 degrees to maybe 89 degrees while blower was on, turn blower off and returned to normal. I never noticed this before, would ye think this is normal?

The VW temperature gauges are conditioned to read a constant 90C once the coolant temperature is truly between 75C and, I think, 107C. When they appeared years ago, on some other makes, they were called "comfort gauges" as the powers that be reckoned that people didnt want to see the gauge moving around a bit as it should even with every thing working perfectly due to the thermostat characteristics.

In your case, if every thing is working normally, then it means that the actual coolant temperature was slightly less than 75C, this if often apparant when the gauge has just reached "90C" and you switch on the blower. If its happening during normal driving (not idling in cold weather) then it could be for any of the reasons listed by the other posters, it could also possibly be the coolant temperature sensor, keep an eye on it as its accuracy is vital for best economy and engine running conditions.
I keep my VWs "for ever" and I replace the thermostat every 5/7 years as after this time the thermostat can be passing slightly even though working perfectly under all other conditions, this ensures an as from new quick warm up.

Bpmull

@john T Carroll not saying your wrong but I find it very hard to believe they would set the gauges up like this. It complete and otherly defeats the point of a gauge if it reads 90 at a range of 75-107 degree c.

berger89

Surely just something to do with the cold air being sucked in? Like in your house..its too warm by the fire so you open a window..the temperature in the room is bound to change

Special Circumstances

Bpmull wrote: »

@john T Carroll not saying your wrong but I find it very hard to believe they would set the gauges up like this. It complete and otherly defeats the point of a gauge if it reads 90 at a range of 75-107 degree c.

There is a significant dead zone in many (most?) manufacturers gauges.
Try reading the actual temperature in torque or something via obd.

Now, in a system with no leaks,correct level of coolant, working water pump and no clogs or leaks things shouldn't really go outside that range except in extreme conditions ... IMO at least.

Edit maybe significant is the wrong word, it's not like it's 50degC +-

John T Carroll

Bpmull wrote: »

@john T Carroll not saying your wrong but I find it very hard to believe they would set the gauges up like this. It complete and otherly defeats the point of a gauge if it reads 90 at a range of 75-107 degree c.

I can assure you that this is certainly correct, and I would thoroughly agree with you that its a pretty useless tool now. I know a few people who got it altered to give the true numbers.
Ther is NO WAY that a thermostat can give a steady reading as it starts to open at around 85C and isnt fully open until around 98C, the reading then will depend on engine loading, ambient temperature, size and cleanliness of the radiator etc, etc.....this is exactly why it was a very useful indicator "in its day".

John T Carroll

Special Circumstances wrote: »

There is a significant dead zone in many (most?) manufacturers gauges.
Try reading the actual temperature in torque or something via obd.

Now, in a system with no leaks,correct level of coolant, working water pump and no clogs or leaks things shouldn't really go outside that range except in extreme conditions ... IMO at least.

Edit maybe significant is the wrong word, it's not like it's 50degC +-

Yes, I can agree with that logic, next step is, of course, no temperature gauge, some, if not all BMWs do not have temperature gauges, also the VW Polo? The modern coolant system is a marvel of consistency, both from the "antifreeze" and the engine management system. I owned a 1980 VW Golf "Formel E" for well over 20 years and I never had to top up the coolant system, I did change the coolant contents twice (G11), but that was it, on the "management" side, I changed (as stated previously stated) the thermostat every 5 or 6 years, the thermoswitch once, (which starts/stops the electric cooling fan) so yes, either put in a gauge that gives the real reading(s) or get rid of it.

Rose35

Thanks for replies, tested my partners Toyota Landcruiser yesterday, temp normal range, turned on heat to max and blower and same thing happened temp gauge moved slightly down, decrease blower flow and temp gauge rises again to normal, also lifting foot off accelerator whilst blower is on full can also alter the gauge slightly. This is only an issue when using full heat with blower on full, I agree if this was happening under normal conditions I would be slightly more worried that I had an issue with the thermostat. Car is running perfectly besides, would I get a warning light if something was amiss with coolant, I would expect an error code of some sort maybe

Special Circumstances

John T Carroll wrote: »

Yes, I can agree with that logic, next step is, of course, no temperature gauge, some, if not all BMWs do not have temperature gauges, also the VW Polo? ....

so yes, either put in a gauge that gives the real reading(s) or get rid of it.

Yup seems to be the way it's going. Blue light - your engine is cold, be gentle. Red light, it's toast in 60 seconds.

Special Circumstances

Rose35 wrote: »

Thanks for replies, tested my partners Toyota Landcruiser yesterday, temp normal range, turned on heat to max and blower and same thing happened temp gauge moved slightly down, decrease blower flow and temp gauge rises again to normal, also lifting foot off accelerator whilst blower is on full can also alter the gauge slightly. This is only an issue when using full heat with blower on full, I agree if this was happening under normal conditions I would be slightly more worried that I had an issue with the thermostat. Car is running perfectly besides, would I get a warning light if something was amiss with coolant, I would expect an error code of some sort maybe

I'm a little surprised to be honest. The only time I've seen a gauge move away from "normal" during driving there were problems.
Fiat - no fan, thermostat stuck open.
Ford - thermostat stuck open.
subaru - growing leak in rad, coolant loss etc.
Edit to add - Honda was venting coolant at traffic lights through a leak in the rad but the gauge stayed rock steady iirc.

Check the coolant level yourself. Don't rely on warning lights. Check the oil too while you have the bonnet open.

Rose35

Have checked both, normal level, getting it serviced next week so will know more, when i say moves slightly down, I mean no more than the one width of the pin........ not a major drop.
My last car ford focus temp gauge went up into red, had leak in rad....
Im just saying if engine temp wasn't normal as should be should I get a warning light of some sort

sean1141

Bpmull wrote:

@john T Carroll not saying your wrong but I find it very hard to believe they would set the gauges up like this. It complete and otherly defeats the point of a gauge if it reads 90 at a range of 75-107 degree c.

If you use vcds to read the coolant temp it will vary in degrees but the gauge will still read 90

Alanstrainor

Rose35 wrote: »

Have checked both, normal level, getting it serviced next week so will know more, when i say moves slightly down, I mean no more than the one width of the pin........ not a major drop.
My last car ford focus temp gauge went up into red, had leak in rad....
Im just saying if engine temp wasn't normal as should be should I get a warning light of some sort

Mention this issue when it goes in for the service, it wont be checked otherwise.

Kevin McCloud

Alanstrainor wrote: »

Yeah, I'd keep an eye on it, probably fine. But the temp shouldn't change once it's warm.

That is incorrect.

I remember had a jap pajero that had a digital aftermarket temperature gauge and when both heaters were turned on demanding heat the temperature would drop for a period.
Makes sense as both matrix's hold water and the one in the rear had a nice run of pipe to it.

John T Carroll

Special Circumstances wrote: »

Yup seems to be the way it's going. Blue light - your engine is cold, be gentle. Red light, it's toast in 60 seconds.

My wife bought a new VW Derby (Audi 50 in other countries) in 1979 and it had no temperature gauge, an orange light was displayed in the dash until the coolant reached some determined level, you were advised not to drive at high engine loads until it extinguished, it was supposed to display a red warning light when things went wrong. Every time you switched on the ignition it did a lamp(s) test (oil pressure, alternator, coolant temp/level etc) as do all cars today when you switch on the ignition

John T Carroll

sean1141 wrote: »

If you use vcds to read the coolant temp it will vary in degrees but the gauge will still read 90

Got my hands on a VCDS this AM and inputted the coolant temperature for a 2005 VW Petrol bog standard Polo. The ambient temp was 5.5C to 6.5C, the temp gauge settled bang on 90C when the real coolant temperature was 74C, it then rose to a real temperature of 83C whilst idling, I then went for a 15 km run in it mainly on the flat driving at the legal limits (two people on board) and the max real temperature that my navigator saw was 85.5C, the gauge never moved off the 90C even with switching the blower speed to pos.4 (from off) while on the move, I didn't try it at idling.

Rose35

Just an update on this issue from last week, had it checked over last thurs and all is normal, this is normal behaviour
in car, required no work or change of temp gauge or any associated parts. Thanks for all the replies.