I have a coolant temp that stays cool now that it's cold out. Is this a thermostat issue?

 

You're saying it never says the car warms up to temp? Even after 10 minutes of driving?

Should either be thermostat or coolant temp sensor.

 

I took it out again this p.m. and temp gauge read normal. This a.m. took it out on the freeway temp came up but never to operating temp/normal. I checked the connection to the temp sensor under the coolant tank. It seemed to have gotten coolant on it from overflow from under tank. I'll see what's up tomorrow a.m. when the temp drops to around 20º.
Thanks. mhg

 

I'm not sure whether it's the thermostat or the coolant temp. sensor but when I got my car it had about 140,000km and the thermostat was not working. On my AEB, they fail in the open position, so in a cold climate makes sense not to get to temperature. When I got the thermostat replaced, it got to normal temperature in a normal time and stayed there.

 

This can be really difficult to diagnose without actually checking voltages and signals or moving forward to opening up the thermostat housing.
Under normal operation, your thermostat acts as a pressure-activated valve that separates coolant in your engine from coolant in your radiator, to allow the engine to warm up quickly and cool down when at operating temperature by allowing flow into and through the radiator.

When your thermostat fails, it remains stuck open, causing coolant to flow freely throughout your engine and radiator and thus causing the engine to take much longer than normal to heat up. Thermostats typically last 150,000 miles. If you don't have a replacement on record in that time, go ahead and change it. When doing so, inspect the part (drop it in a pot of bowling water and see if it clicks open). If the thermostat seems to work, the problem is the coolant temperature sensor. In this way, you won't tear into the car for no reason, and you'll have the peace of mind of new cooling system components keeping your engine at proper temperature.

 

I think my thermostat is stuck too.
It gets up to 60° when driving, 70° on a highway, this is in less than 20°C outside temps.

So I covered the radiator with a sheet of thin board and now it gets up to 90°C and stays there, and the heater works too...

Though the engine does take a lot of time to heat up, I expect that's because it has to heat everything at once.
Since I think the timing belt needs to be done (I have to see it first, I just bought the car) I will do everything at the same time.
Considering, it does not look that hard to do, the belts expensive compared to my last car.

 

If you are going to do the thermostat you will need the cam lock tool and the crank shaft lock. You can get them on ebay or amazon. Also there is a tool company in Colorado Springs that sells the VW/Audi oem tool. You will also need the cam chain tensioner tool (2) if you follow the recommendations below. And you will need a serious pulley remover for the cam sprockets.
Since you just got the car as you say you are probably looking at 15K miles or so I'm guessing.
My experience was that I changed the top end gaskets (cam covers), cam seals, half moon seals, timing belt and serpentine belt. Reason being the half moon seals in particular shrink and leak down the front onto the timing belt diver side and rear at the passenger side. Since your there you might as well take care of biz.
Beside the thermostat you want to check your water pump DON'T REMOVE unless it is leaking from the weep hole. Also, check your coolant reservoir sometimes the tank gets cracks and may leak into the connection below where the sensor is. This can give you a check engine light. Most likely it's your thermostat which has stuck open and it's behind everything under that hood that you can think of. It will run you $30.00 for the thermostat and the o-ring. It's the work that the shop will hit you hard on.

If you need a manual Bentley sells one through Amazon.

Here is a link for the timing belt and thermostat/water pump removal and installation. It's pretty thorough and gives solid advise. You will need to use the links on this page to pull the bumper off and put the car into "service position".
Audi A4 Timing Belt Installation Instructions for 2.8L 30 Valve

You will need to flush and refill your coolant. USE ONLY AUDI/VW COOLANT.
If you don't you will shred the seals in your water pump. There is a link on this page on flushing your system and refill procedures.

As for the gaskets and half moon plug replacements refer to the service manual or check youtube for step by step. A6 replacements are what you can see I believe. It's pretty much the same engine. 3.0 not 2.8. Blauparts may have a step by step also. Use the link above to check around.

Make sure you have metric allen keys for sockets as you will need them for the flush and refill. The front allen bolt is a pain because it is off set where the distributor block is.

My advise is TAKE YOUR TIME. Have some cardboard there to set all of the bolts into for the various fan tensioners, fan pulleys, valve covers (if you do the half moons) and so on. It's a three hour job for a shop with four hands and experience. I have taken at least 8-10 hours to do the job. I've done it twice on my own.
Good Luck. You can do it with a little patience and perseverance.
MHGABAL

 

Thankyou MHGABAL,

I priced the whole cambelt kit today at NZ$970...(US$700) From Repco spares.
Last one I got for my Mitsubishi was 1/3rd that price and more parts...
There's another generic kit for $600+ around too.

Thanks for the changing the cambelt link too. It actually looks easier than the mitsi.