Is My Thermostat Broke?

[chocolate_o_brian 0]

I'm still struggling to get any sort of respectable fuel economy in the cold weather, even though I have replaced a few things like the whole SAD and ECU temp sensor (and plugs) etc.

 

So I have noticed that the coolant never seems to rise over 69-70 degrees (or the 3rd bar on the gauge) in the cold weather, no matter how long or fast I drive for. Now if it's left to idle long enough in say traffic, then ofcourse eventually the temp rises and I kick in the manual fans. But for normal driving around from cold, it never seems to get above said temperature. This means that the oil (again unless I'm driving for a prolonged distance) never seems to get warm (or above 50 degrees as per the gauge).

 

It's led me to think is it stuck open perhaps? Or is it simply a case that the weathers cold, so any air going into the radiator is simply not allowing it to get to a temperature (82 degree thermostat) where the stat needs to function.

 

Anyone else suffering with these symptoms? I wanna see others opinions before investing in another stat and no doubt 2-3 litres of antifreeze too

 

Thanks in advance

[The Arch Bishop 0]

Mine is exactly the same but I'm loathed to fiddle with the thermostat cover. One of the threads appears knackered and it's siliconed in place. I'm guessing the thermostat is either stuck open or missing entirely.

[chocolate_o_brian 0]

Mine is exactly the same but I'm loathed to fiddle with the thermostat cover. One of the threads appears knackered and it's siliconed in place. I'm guessing the thermostat is either stuck open or missing entirely.

 

The funny thing is that I bought the car in June 08 when warmish weather was here. It came to around winter and similar symptoms appeared along with a coolant leak. I took off the thermostat cover and nothing was there! Not stat, or rubber gasket, so I knew where the leak was. But when the stat was put in, the engine temp warmed nicely. It was warmer than it is now when I did this, hense my questions.

 

I'm tempted for the sake of a £12 stat and 2-3 litres of coolant.

[welshpug 1,657]

is it a 1.9 with an air-oil cooler?

[Bottrill 0]

I have recently had a new thermostat in my 1.6 GTI (1990) the temp gauge rises quite quickly to that third bar, the thermostat opens, and it drops very slightly to below the line. It then recovers back up to a fraction over the third line under normal driving. It's just how they are i assume.

 

Lee.

[DamirGTI 342]

Sounds like 82deg stat mine was at 70deg whilst driving as well , but the oil temp was fine , i dare to say a touch too hot but that's another subject .. switch to the 88 or 89deg stat and try it out that'll keep the water temp at around 85 mark during the driving which is nice for better heating now during the winter time .. dunno about consumption benefits though .. and afterwards , again , switch over for 82deg stat for the summer time ..

 

Damir

[chocolate_o_brian 0]

is it a 1.9 with an air-oil cooler?

 

It's a 1.9 yes fella.

 

Basically theres an adaptor on the sump where the oil filter attaches. This has 2 pipes going from it which bypass a coolant pipe. Does that mean it's water cooled as the oil pumps round these 2 pipes around a thicker coolant pipe?

 

Damir, I believe it is an 82 deg stat as when it's warm, the stat opens when it's on the 4th bar.

 

The below pic explains it better (it's not my facia, just one I found).

 

Where the red arrow is on the temp guage is where the stat is opened when warm. Is the temp it run at when upto temp (82 degs). But the yellow Arrow is where it gets to now, max 70 degs?

 

Also, where the yellow line is on the oil guage is where it is in the summer when upto temp after a few miles. Where the orange dial is, is where it seems to stay now unless driven on the motorway or at 60+ mph.

[Anthony 1,003]

In my experience, 82 degree 'stats sit on the 3rd line (ie the yellow line on your picture), and 89 degree 'stats on the 4th line (ie the red arrow)

 

Oil temperature barely moving when bumbling around is perfectly normal during the winter, particularly if you've an alloy sump or an air-oil cooler fitted.

[chocolate_o_brian 0]

In my experience, 82 degree 'stats sit on the 3rd line (ie the yellow line on your picture), and 89 degree 'stats on the 4th line (ie the red arrow)

 

Oil temperature barely moving when bumbling around is perfectly normal during the winter, particularly if you've an alloy sump or an air-oil cooler fitted.

 

Am I interpreting the picture wrong Anthony, as I look at it and see 7 lines, the 4th one being the 80 degree line.

 

 

The above is a better piccy I found on the net. I see 7 lines, the 4th one being the middle and 80 degree line. The dial is sat on the 1st one which is 50 degrees, and my current temp never goes above the 3rd one which is 70 degrees. So basically my thermostat (if it's not broken) NEVER opens up, regardless of how long the car is driven or if the oil temp is upto temp too.

 

Sorry if I sound patronising, it's not intentional. It's just in warmer weather the coolant level is always around the 4th line or 80 degrees, maybe I'm reading the image wrong.

[DamirGTI 342]

Mine is like this :

 

 

Water temp (while driving) - @ blue line with the 82deg stat , @ red line with the 88deg stat

Oil temp - when driving moderate @ blue/red line which is roughly in the center of the gauge , when driving fast @ orange line .. but do note that the labeling of the dials on the oil temp is wrong , so the middle mark is 90deg .. and so is the last mark which should be 140deg not the 150 ..

 

Damir

[jord294 92]

hmmm ? your oil temp seems to get a touch high imho

[chocolate_o_brian 0]

hmmm ? your oil temp seems to get a touch high imho

 

Agreed. Mine hits about 100 tops with spirited driving.

 

What I don't get then is why the 82 deg thermostat opens at 70 degrees on the dial. I thought it would open just after the 80 degree dial?

 

Unless I have an 89 deg stat?? Doubt it, but a possibility.

[DamirGTI 342]

hmmm ? your oil temp seems to get a touch high imho

 

.. yes it's a modified engine (high CR ported head and some other stuff ..) so it heats up oil a bit more that before , will need to fit oil cooler back and switch to full synth oil although it wasn't as high as it is now before running on Shell semi synth , things has gone up a bit on the gauge since i filled Mobil semi synth inside

 

Damir

[Bottrill 0]

In my experience, 82 degree 'stats sit on the 3rd line (ie the yellow line on your picture), and 89 degree 'stats on the 4th line (ie the red arrow)

 

Oil temperature barely moving when bumbling around is perfectly normal during the winter, particularly if you've an alloy sump or an air-oil cooler fitted.

 

 

 

+1.

 

They are analogue gauges, so not 100 % accurate anyway. All these gauges in our cars will differ slightly due to manufacturing tolerances. Another thing to consider is the efficiency of the radiator too once its warmed up.

[chocolate_o_brian 0]

Well I got 24.1mpg last week, so it seems consistant. Thing I don't get is it's only slightly higher than when the car was previously idling upto 2000prm until warm. I'm glad the idle issues are resolved but still converned I'm getting the same mpg as my old Impreza Turbo did in the cold. Just hoping it's not causing the engine any damage.

[chocolate_o_brian 0]

The cars seeing around 25mpg at the minute which isn't great but it's better than before (with knackered switches as per other thread).

 

I popped to a local motor factors yesterday and got another 'stat and 2 litres of anti freeze for the princely sum of £10.62

 

Just gonna go swap the stat and take the car for a run. At worst it will be the same and I'll be £10 lighter, if better the water temp may be a bit more settled and give me better mpg as the car is upto temp quicker too.

 

Will report findings in a few hours

[chocolate_o_brian 0]

Reports are as follows...

 

Definitely made a change

 

Took old 'stat out (was an 82 deg one), and put new one in (also 82). Refilled coolant tank with 50/50 water and anti-freeze (about 2 n a bit litres had been lost so not bad) and bled any air bubbles out. Car idled like mad for a min or two but once I took her out this sorted itself out quickly. I'll monitor the idle speed if necessary.

 

Anywho, car wasn't warmed up or anything before taking her out. After a mile or so, the water temp was back upto 80deg and not 70 as it's been for a while on the old 'stat. After 3-4 miles, the oil guage actually moved and read about 70 deg which hasn't been happening for a long time (after 4 miles anyways).

 

Give her the beans on a couple of 70 limit dual carriage ways and a few backroads. The water temp stayed between 75-85 degs and oil came up nicely to about 90 deg.

 

So definitely something not right with the old stat and the car seemed smoother to drive as she warms up properly again. Will keep tabs on the mpg over the coming weeks and hopefully see an increase.

[alphacharlie 0]

Nice one matey, I've seem to be having similar issue to you just a few months behind!!

So far I've got a SAD ready to change and collecting an ECU temp sensor tom, may as well get a new thermostat to boot and change it all in one go, then I may be able to get the car out of the garage in the mornings without a load of hassle and not sit at every junction at 2000rpm

 

Cheers

AC

[chocolate_o_brian 0]

Nice one matey, I've seem to be having similar issue to you just a few months behind!!

So far I've got a SAD ready to change and collecting an ECU temp sensor tom, may as well get a new thermostat to boot and change it all in one go, then I may be able to get the car out of the garage in the mornings without a load of hassle and not sit at every junction at 2000rpm

 

Cheers

AC

 

Making sure the ECU temp sensor and plug are in good working order really helps. Then the plug that goes into the SAD too - they're both the same as Simes sent me 2. I did a little soldering and it worked wonders.

 

I would suggest when you've got the bits done and swapped to go to a garage and have the idle control speed and fule mixture screws (Co2) checked. This will sort both your fuel economy and idle issues out. I may pop back and have mine rechecked or possibly just adjust the idle as it seems about 100-200 higher now it's upto temp quicker.

 

Costs me a £5er at my local MOT station for what? 10 mins work

[DamirGTI 342]

Sounds like the old stat was stuck open all the time

 

Anyway , glad you've sorted it , and nice of you for sharing the final repair solution/report with us

(could recommend this to all of you people , for the benefit of all the readers , as a lot of stuff which can be found via search based on similar issue hardly has a report on the end with explanation what was really solution for fixing the problem in the first place ..)

 

Damir

Edited February 7, 2010 by DamirGTI

[chocolate_o_brian 0]

Sounds like the old stat was stuck open all the time

 

Anyway , glad you've sorted it , and nice of you for sharing the final repair solution/report with us

(could recommend this to all of you people , for the benefit of all the readers , as a lot of stuff which can be found via search based on similar issue hardly has a report on the end with explanation what was really solution for fixing the problem in the first place ..)

 

Damir

 

No problem. Think it was either stuck open totally (due to the cold temperatures form a few weeks back perhaps) or partially open.

 

Anmywho, took the Mrs to work just now which is the cars coldest journey on a day. Same thing, highish idle of around 1500rpm for a mile or so, then settled to around 1100rpm. Water temp upto about 80 degs and idle sorted. For the first time in a long time, the oil temp gauge actually moved to around 70 degs by the time I got home, so this is proof in the pudding so to speak that the engine is warming up properly.

 

Definitely worth it for the sake of a couple quid.

[jord294 92]

No problem. Think it was either stuck open totally (due to the cold temperatures form a few weeks back perhaps) or partially open.

 

Anmywho, took the Mrs to work just now which is the cars coldest journey on a day. Same thing, highish idle of around 1500rpm for a mile or so, then settled to around 1100rpm. Water temp upto about 80 degs and idle sorted. For the first time in a long time, the oil temp gauge actually moved to around 70 degs by the time I got home, so this is proof in the pudding so to speak that the engine is warming up properly.

 

Definitely worth it for the sake of a couple quid.

 

personally, i don't find that my oil temp rises much at all, unless i give the car a good thrapping.

 

then it will only move about 1/3

[Simes 248 2 Cars]

No problem. Think it was either stuck open totally (due to the cold temperatures form a few weeks back perhaps) or partially open.

 

Anmywho, took the Mrs to work just now which is the cars coldest journey on a day. Same thing, highish idle of around 1500rpm for a mile or so, then settled to around 1100rpm. Water temp upto about 80 degs and idle sorted. For the first time in a long time, the oil temp gauge actually moved to around 70 degs by the time I got home, so this is proof in the pudding so to speak that the engine is warming up properly.

 

Definitely worth it for the sake of a couple quid.

 

Nice one.

 

If you have your old thermostat you could test it by boiling it up in a saucepan and seeing when/if it opens.

[alphacharlie 0]

GSF tell me they only stock an 87 deg stat so if I maybe I wont do that job this week.

AC

[welshpug 1,657]

GSF tell me they only stock an 87 deg stat so if I maybe I wont do that job this week.

AC

 

but did you ask if they can order one in?