Temperature gauge not in the middle

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TRiBaL
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Re: Temperature gauge not in the middle

Post by TRiBaL »

From what you described it never really warms up. Typical for stuck open thermostat.
Normally, the needle should always be in the middle (90degrees) and it should warm up relatively fast (6-7 minutes) no matter how cold the weather is.
They are designed this way to prevent overheating when they fail.
There is also a coolant temperature sensor which often fails but this usually shows difficulty starting when the engine is cold etc. It may also trigger a warning dash light.
IMO it's the stat.
Mine also did around 350max with the faulty stat. Now it does 400, easily
Last edited by TRiBaL on Thu Jan 14, 2016 12:03 pm, edited 1 time in total.
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alexperkins
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Re: Temperature gauge not in the middle

Post by alexperkins »

It could be the sensor, but its worth considering the thermostat too. I would agree with TRiBal on this
Daves1991
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Re: Temperature gauge not in the middle

Post by Daves1991 »

Haven't had any problems starting the past couple of really cold days. The car warms up fine, get hot air blowing through without any problems within 5-7 min. No warning lights coming up, and it had MOT done right before I bought it and passed with 0 advisories.

My journey to work includes a lot of starting and stopping driving through towns, so I'd contribute the mileage to that.

But I'll have my mechanic take a look at it tomorrow, I'll let you know what he says.

Thanks for the help, much appreciated.
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alexperkins
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Re: Temperature gauge not in the middle

Post by alexperkins »

When the sensor fails you can get all kinds of funny behaviour like the gauge creeping, swinging and doing various things

If the temperature creeps up when sat in traffic, then drops again when moving its almost certainly the thermostat playing up.
TRiBaL
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Re: Temperature gauge not in the middle

Post by TRiBaL »

Hot air blowing is not an indication that your stat and/or sensor are working perfectly, provided your gauge is not faulty. Also, hot air blowing is not an indication that engine has reached normal temperature. It may blow hot air even at 70 degrees if the stat is not opening and closing on time. If i where you and the car is second hand i would change both but in my opinion its most probably the thermostat. Your mileage is too high for its usual lifespan. Check it out and keep us posted.
Daves1991
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Re: Temperature gauge not in the middle

Post by Daves1991 »

So I went to see my mechanic after work (he had some spare time) I told him the issue and said that its either the sensor or thermostat as you guys did so he booked me in to have them both changed, meanwhile I left my car running because I wanted to get into a nice and warm car and the temperature went up to mid 90s for the first time I've seen it, but as soon as I started driving it shot down to its usual spot.

Exactly as you said Alex... Alan Wong said you knew your stuff ;)

And Thanks for all the info and help TRiBaL :)

So I'm definitely getting the thermostat changed :D

And regarding the mileage, the previous owner bought it from new 15 years ago and used it to drive to work everyday, quick math would indicate he did around 8000 a year, so can understand why it's so high. Just had timing belt and water pump changed as it is coming to 120k but not bad for £650 :)

Thanks again!
TRiBaL
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Re: Temperature gauge not in the middle

Post by TRiBaL »

By high mileage i meant the thermostat not the car. Glad we helped you out! :)
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alexperkins
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Re: Temperature gauge not in the middle

Post by alexperkins »

Team work 8)
Daves1991
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Re: Temperature gauge not in the middle

Post by Daves1991 »

Ahahaha now that I read it in context that makes perfect sense...
TRiBaL wrote:By high mileage i meant the thermostat not the car. Glad we helped you out! :)
gti1999
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Re: Temperature gauge not in the middle

Post by gti1999 »

Hi there,

I would like an opinion on a particular situation.

I have a vw polo gti from 1999 6n1 Mk3 1.6 125 hp.

I bought the car last year and the temperature was always in the center 90*. Now it's the first time i'm in winter season and the temperature drops on the highway.

I have changed the thermostat 2 times and the temperature sensor (all original parts from vw), plus a new radiator fan was installed. We did all the tests we could at the garage with the mechanics, but they say it's normal to drop like that. We also tested the fan to see if the 1st and 2nd march were alright and they are. we even disconnected the fan and entered the highway to test and still the temperature dropped btw 70º and 60º

I have serious doubts about it, my mother's car is a normal 1.0 Polo Mk3 and the temperature stays at 90* all the time. I understand that mine has a bigger radiator and there is less struggle for the engine while driving at low rpm.

Howver, i would like to know if this is normal in winter with the cold.

Should these cars, and especially my model in particular, stay always at 90º under any kind of conditions?

Thank you!
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alexperkins
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Re: Temperature gauge not in the middle

Post by alexperkins »

That’s not normal

Did you have the thermostat housing changed also? If they break the pin gets jammed and forces the thermostat to stay stuck open
gti1999
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Re: Temperature gauge not in the middle

Post by gti1999 »

TRiBaL wrote: Thu Jan 14, 2016 8:48 am Have you ever changed your thermostat?
That's the only thing i didn't. I told many times the guy there about this part.

All he said was that it was just a reservatory, and since it had no holes no problem then and that the thermostat is original and well attached to it with the 2 screws on the cap.

I had serious doubts and wasted money on 2 thermostats because of all these, even had to make new holes because the old screws didn't fit anymore.

Can you explain me with detail what you mean by pin?
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alexperkins
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Re: Temperature gauge not in the middle

Post by alexperkins »

F258409A-A150-4C87-90BA-2A9BC91223C1.png
You need to replace the entire coolant sensor housing and the thermostat housing too

It all locates within a housing and over time it breaks down inside so there’s nothing for it to locate against
gti1999
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Re: Temperature gauge not in the middle

Post by gti1999 »

Do you know a place where i can buy the 2 original parts for my car?

Thanks a lot for the help!
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alexperkins
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Re: Temperature gauge not in the middle

Post by alexperkins »

Pop a photo up of your car. I need to check what series it is as it says you are in London as the 6N GTI wasn’t sold here. Only the 6N2
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