Definitely thermostat?

[Matt82]

Being a sad act I had a look at what temp was being reported to obd this morning

1 degree to 2 degrees outside moving in traffic at 20 to 30 mph the water temp got to 85-86 with the heater on hot

Once you'd put some load onto the engine it went up to 86 and when you were coasting etc it went down to 85

I think it's an 86 degree stat from memory and the gauge sat at 90 the whole time

 

[Alibaba99]

Thought about blocking off part of the radiator?

That's fixing the symptoms not fixing the problem. With our temperate climate there really shouldn't be any need to block off the radiator during winter as the thermostat should be doing its job.

You also need to be wary that it isn't just the rad being blocked but also possibly intercoolers, oil and transmission coolers plus the aircon rad.

 

[loltim]

Or the car is just overcooled. My A4 does this (only very slight drop in temp when moving, on very cold days like today), and the thermostat is absolutely fine.

I'm not sure that's even a real thing. The thermostat should control the temp. Sounds broken.

 

[Janesy B]

I wouldn't even put up with the needle moving around in an old Ford, I really don't believe it's overcooled seeing as temps haven't even hit freezing yet.

 

[Minstadave]

This^^ you can also use the climate control panel to display a coolant temp reading as well. Should sit around the 90 degree mark. Could also be the impellor of the water pump breaking off, they are plastic on vw. ECP/GSf do one with a metal impellor.

Go for stat and sensor first

Alex

This is got me wondering what could be causing mine. I've changed the stat and the sensor but it still drops to 1/4 of the dial most mornings the last 2 weeks. Changing the water pump and flushing the coolant system isn't a cheap job, I think it'll have to wait until the next cambelt change.

 

[miniyazz]

Thought about blocking off part of the radiator?

Already did; I did avoid the section that does the air con

 

[miniyazz]

The gauge is "buffered" as we, so rarely reads accurately.

they usually show full temp by about 60*, so if yours is going left of centre, it could be pretty cold

its hardly the end of the world though, but your heater wont be as warm

That seems suspiciously low to show normal operating temperature. By 60°C mine would be barely above the white lines at the cold end and not reach its normal operating position until at least 80°C. It will of course stay there up until at least 106°C (the highest temp I've recorded) which fits given the thermostat should be fully open by 105°C and that's when the fans come on..

 

[Daff_Duck]

For what its worth I have an A4 diesel and like many I thought it was the thermostat got the old one out and stuck it in boling water to check if the valve opened which it did but decided on a replacment as everything else checked out fine water pump is not an issue as its only just been replaced.

But I am still stuck with the very very slow warm up of the engine and can take up to 6 miles before it gets to the 90 deg opearating temp, therefore I can only assume its just one of those things I will have to put up with.

 

[paradigm]

temps haven't even hit freezing yet.

Yes they have, a number of times.

I've done a bit of investigating with mine. If I turn off the supplementary heater, and the climate control (totally off, no fans, no nothing), and put Drive Select into Dynamic (rather than my usual Economy), the car heats up a lot faster, with a much more stable needle. It's still taking 15 minutes~ to get to temperature though.

If I run the engine in Economy mode, it takes literally forever.

 

[wildman_33]

For what its worth I have an A4 diesel and like many I thought it was the thermostat got the old one out and stuck it in boling water to check if the valve opened which it did but decided on a replacment as everything else checked out fine water pump is not an issue as its only just been replaced.

But I am still stuck with the very very slow warm up of the engine and can take up to 6 miles before it gets to the 90 deg opearating temp, therefore I can only assume its just one of those things I will have to put up with.

My Polo is exactly the same. Its because the engine generates relatively little heat. I know VW started fitting auxiliary heaters in the the mk5 golfs so that the cabin would heat up in a reasonable amount of time, my car was from before then so I have to put up with freezing until then. Its worse if you hit traffic, my engine has taken 30 minutes to get up to 90C in slow moving traffic in the past, it seems to need a reasonable amount of load to get to temperature.

 

[miniyazz]

Diesels are of course notorious for taking a long time to warm up. The V6 petrol in my Golf is not

 

[Matt82]

Diesels are of course notorious for taking a long time to warm up. The V6 petrol in my Golf is not

like

 

[miniyazz]

So, thermostat changed for the kingly sum of £60 (I must use this garage more often ) and it's now heating up as normal
Fully warmed up well within a 5 mile round trip with a short break in the middle at roughly 25mph average, more like what I'd expect (so within 10mins, to all you diesel sufferers, and that's without stationary traffic or high engine loads )

 

[Matt82]

Shoulda done it yourself and showed up pics of how comedy packed your engine bay is

 

[miniyazz]

As you wish:

Spoiler

Actually this points to the coolant sensor but the thermostat is just to the right. As you can see, much easier access with the front off!

Doesn't really show it properly but comedy tight engine bay