17 miles to reach 90c, Stat is in the closed position

[billybaggins]

My car has taken 17 miles of 30-50mph driving to reach 90c, then i stopped at traffic lights and it dropped to 85c or so. Removed the stat yesterday and it was closed whilst cold and was very recent looking.

Could this be the cts or is it just likely to be the cold weather and the viscous fan constantly cooling? My last few cars have got to 90 in a few miles and stay there.

Its a 1.9 tdi 110, is this normal?

Thanks

 

[aragorn]

Broken stat.

 

[billybaggins]

Broken stat.

So thats definitely not normal on these cars? The stat is fairly new and was in the closed position, but i suppose they can fail still at a yong age

 

[aragorn]

I've had them fail right out the box.

The gauge should never move from 90 once its warmed up, and it should hit 90c in less than half the time you've suggested.

 

[billybaggins]

Thats what i thought. Even though its in the closed position when its cold it can still be goosed? and still should heat up considering how cold it is outside?

Cheers for your help, saves me a bit of messing about putting the wrong parts in.

 

[ScottD3]

Seems normal for a diesel.

My 110 TDI does the same thing when its this cold.
Takes ages to warm up and it will even get cool again if left idling.
Only happens when its as cold as it is at the moment.

Same thing happens to the B6's.

 

[billybaggins]

Seems normal for a diesel.

My 110 TDI does the same thing when its this cold.
Takes ages to warm up and it will even get cool again if left idling.
Only happens when its as cold as it is at the moment.

Same thing happens to the B6's.

And have you changed the stat at all to see if that was the cuase or have you just let it be? I just feel on my commute each day which is 17 miles each way , if the car doesn't get up to temperature im just using excess fuel which defeats my purpose of having a diesel.

 

[ScottD3]

And have you changed the stat at all to see if that was the cuase or have you just let it be? I just feel on my commute each day which is 17 miles each way , if the car doesn't get up to temperature im just using excess fuel which defeats my purpose of having a diesel.

It was a new OEM state and its done it ever since.

There is a couple of posts about this around the B6 section and general thinking is its normal.
My trip in to work is about 15 miles with a ferry trip in the middle.

When I sit waiting for the ferry I sometimes got the engine running depending on the temperature to keep warm and I can watch the temp gauge drop down to about 60degrees again.

 

[billybaggins]

just doesn't seem right to me, but maybe that's just the nature of the beast. Pretty sure they wouldn't have done that from the factory, so something must have changed.

 

[aragorn]

yes, something has changed, the thermostat is broken.

Idling for long periods with the heater etc on will ofcourse cause the engine to cool down, as deisels run very cool at idle. But the way the temperature guage works, you should never see that cooling effect on a normal drive just by stopping at some traffic lights like you suggest.

The first thing you need to understand is the dash lies. it displays "90" at any temperature between about 80c and 100c. So if it moves from 90, its dropped BELOW 80c. As a result, a normal car working correctly should never move from the 90 position.

When stats get tired, they often open early. IE instead of opening at 90c, they might open at say 74. I've had a few stats that have lasted a year or so, before allowing the temperature to drop to around 70-75 while on the motorway. Lower speed roads the guage would show 90, but infact the coolant was hovering around 80c.

You can view the actual temperature on your climate control display if your car is so equipped. Hold recirc button and press the up arrow. Display will change to 1C, use temp +/- control to make it read 49c then press recirc button again. Display will now show coolant temperature.

 

[ScottD3]

just doesn't seem right to me, but maybe that's just the nature of the beast. Pretty sure they wouldn't have done that from the factory, so something must have changed.

going the masses and my experience with really cold days it seems fine.
Granted 17 miles might be a bit extreme for it not to warm up.

Its just going by the masses when other threads like this came up, it seems normal.

 

[aragorn]

17 miles is NOT normal.

if its not hot by 10 theres something wrong, half that for a petrol.

 

[billybaggins]

17 miles is NOT normal.

if its not hot by 10 theres something wrong, half that for a petrol.

That was quicker on the way home today, i got to carry a bit more speed.

I got into the on board diagnostics in the climate control and went to no49 for temperature and interestingly when the gauge reached 90 the onboard said 79 and didnt go over 80c.

I assume thats what the fuelling from the ecu is reading off? Would that sound like a temp sensor fault? cheers

 

[Mikemc]

I just popped out in my 140 bkd, less than 4 miles even stop starting 3 times to nip in shop , when home it was just above 50 degrees

 

[aragorn]

That was quicker on the way home today, i got to carry a bit more speed.

I got into the on board diagnostics in the climate control and went to no49 for temperature and interestingly when the gauge reached 90 the onboard said 79 and didnt go over 80c.

I assume thats what the fuelling from the ecu is reading off? Would that sound like a temp sensor fault? cheers

No, it sounds like a faulty thermostat!

 

[aragorn]

I just popped out in my 140 bkd, less than 4 miles even stop starting 3 times to nip in shop , when home it was just above 50 degrees

Bout right, given its near 0c outside. Doing the same again would have seen it to 90.

 

[B5NUT]

From 0 to 90 takes me about 6 miles, that's 1 mile of stop start then 5 miles on the motorway at 65-70mph, do that trip every day and it's always the same. That's a 1.9 PD engine

 

[billybaggins]

No, it sounds like a faulty thermostat!

Cheers for all your help aragorn, but excuse my stupidity over the cooling system. But if the coolant was at 90 and the needle says 90 but the ecu says 80 would that not be the sensor giving off the wrong info?
Thanks again

 

[Nessy]

From 0 to 90 takes me about 6 miles, that's 1 mile of stop start then 5 miles on the motorway at 65-70mph, do that trip every day and it's always the same. That's a 1.9 PD engine

That's about the same for me, 1.5 miles of urban (<40mph zones) and then onto motorway at 70 mph, and has been the same for me the last 7 years I've had my A4.........17 miles is nuts!
I always use a Genuine 'stat but even they don't seem to last as long as they used to, I'm on my 3rd one in 7 yrs (100k miles) of ownership on the A4 yet my 80 TDI only used 1 in 5yrs (also 100k miles).

 

[NineNails]

I'm on my 3rd genuine stat in a year!

But if the coolant was at 90 and the needle says 90 but the ecu says 80 would that not be the sensor giving off the wrong info?

As aragorn has said... The temp gauge should only be thought of really as a rough estimate, indication. The temp sensor reading you access on the climate control is far more accurate. It sounds like your thermostat is opening too early and is faulty. This is being backed up by the needle behaviour you describe. I've had experience of pretty much every type of stat failure of late lol

 

[Mike B]

Stats are basic just some wax inside so they can leak and thats why the coolant doesnt heat up quickly .Always worth changing if its in doubt.My 2.5tdi gets to 90 wellunder 10miles even in this weather.Has a genuine stat fitted by Chris last year