Lazy thermostat - keep an eye on yours!

The wife took her 170 sport to the dealer yesterday as it has a lazy stat, now the temp has dropped the car really struggles to get warm, plus it just about reaches 90 on the motorway, but as soon as you slow down the temp drops, I had the same issue on my 1.9 A4, chanee the stat on that and it's like a rock now, glued to 90 no matter what I do with the in car heater..

So booked the wife's in via the telephone booking service at my local garage, Chilwell seat, the wife dropped it off and explained exactly the issue. When she went to pick it up they told her there was no issue and its a feature of the engine that it cools down..... So I paid a visit and politely told them the same as the wife did and explained where I worked etc.. And the car is now booked in for a new stat on Thursday.

The garage said it was the first they had heard of this problem, so can others check their cars and if needed report the issue to seat for a new stat, the main issue is slow to come up to temp, and once up to temp if you put the heater of full you can drag the temp back down to 70 deg or so.

Karl

We shall see but I'm sure it's not a feature... As there's no way in hell it would have got the claimed figures on an emissions test if it can cool off so much.

Nah it can't be right, it shouldn't cool down once its at 90, my a4 doesn't now I've changed the stat, the whole idea is it shuts off the water to the main rad unless its over 90, and the in car heater won't be that good at cooling!

wife has just text me, they are placing the thermostat, so fingers crossed this make things a bit more stable!!! if it doesn't and it is a "feature" of the car then it's a bloody crap one! very poor engineering design that is for sure!

I'm sorry loony your wrong, while the stat is closed the water should only go round the engine, oil cooler and in car heater, the in car heater is a rad, but it is a small one, very small, and unless the air coming out is very hot and you have the in car heater set to hi there is a electronic valve which will partly shut the flow of hot water to the in car rad to regulate the temp in the car.

When the car water temp goes above 87 deg the stat will START to open, and be fully open by about 93 deg, this allows water from the block to enter the main rad at the front of the car, the water leaves that rad at very low temps, circulates back round the system and lowers the over all temp.. Once it's back bellow 87 the stat will be closed to raise the temp back up..

You will really struggle to drag the temp low using just the in car heater unless its very cold outside and you stick it on high with fans on full! My Audi won't budge now, and its not that wasteful on fuel compared to the exeo... In traffic it does better mpg! Ergo it must burn less fuel that exeo, less fuel means less overall heat, yet mine still reaches temp.

The coolant flow on the exeo is a little differnt to a4, but over Christmas I will map both to see if the exeo has a major design flaw, but I very much doubt it!

Exeo is back this eve so we will see what happens tomorrow when we are out...

You would never put it where it would get a false reading, ie between stat and main rad, that temp sensor is used to control the fuelling of the car so why would you have warm water in the block, but have the computer think its still cold in the block?

I can check the parts list but I will put money on it using the standard temp sensor that all vag cars use, the 4 wire one where 2 wires got to the dash and 2 to the ecu, and no you couldn't get a different reading of each set of wires... There's only one sensor and 2 outputs.

Like I say I will see how it goes over the next few days,

Been out today, went about 10 miles down the road, was at the dual carriage way in a mile or so and already the temp was just off the stop, and I was driving normally. It's defo coming up to temp better at the moment (6 to 7 deg Amb temp) be it was up at 90 deg after about 5 mins at 60mph, also when hot it didn't cool down around town, and I could only drag the temp down with the heater on full heat, full fans and every vent open! And that was at idle... With the heater set to auto, econ and 23 deg it wouldn't budge from 90, so it looks like it could be the same lazy stat problems the audis have..... If your still wont be stable I would push to have the stat changed, it was Nottingham pentagon seat Chilwell that did mine under warranty,

Karl