A3 1.6tdi (2010) overheating coolant warning light

**Jblakes84** · 22-01-2020,07:49 AM

Morning all,

Hopefully somebody can help me. When I go for a decent run 20 miles plus. The car sits at 90degrees C, then suddenly starts going up and then the warning coolant signal comes on, not sure this is linked but my first thought was turn heating off (this has been cooler than usual) and open window. The temp gauge went down to 90, guessing that's not linked.

Anyways when I stop the fan at the front of engine goes crazy for about 30secs then stops, looked under bonnet and nothing seems obvious, the cooland level is also top of the level so guessing that's not the issue.

Any advise on where to start?

Regards
James

**jonathanfenton** · 22-01-2020,08:30 AM

Sounds like a failed/failing water pump or thermostat. Especially if heater hasn’t been as good as it used to would indicate poor flow of coolant.

**Jblakes84** · 22-01-2020,08:42 AM

Thanks for the reply, is there anyway to tell which one it is? I know when you do water pump you generally do timing belt, which isn't due for 25k, so don't want to just do it to see if it's that.

Regards James

**jonathanfenton** · 22-01-2020,08:57 AM

When you did last belt change did you change pump?

**Jblakes84** · 22-01-2020,09:10 AM

About 60k ago, or 4years ish.

**jonathanfenton** · 22-01-2020,09:45 AM

Well cheapest and easiest job is to try thermostat. If that doesn’t resolve there’s really only one more component in my opinion that could cause your symptoms.

**Jblakes84** · 22-01-2020,09:58 AM

That's probably the way to go. What about a doggy temp sensor, could that cause the issue?

**jonathanfenton** · 22-01-2020,09:59 AM

That gives your erroneous temperature readings, wouldn’t cause your heater to be cold I wouldn’t have thought. I’f you set your heater to max or hi does it blow hot air or still lukewarm?

**Jblakes84** · 22-01-2020,10:10 AM

It's lukewarm, not as hot as it used to be. The car stays on 90degreec when warm the goes upto 130c, for about a min then once I stop heater (maybe nothing to do with it) then it will drop back down to 90c, sometimes coolant warning comes in, sometimes it goes down in temp to not cause it to happen. Kinda weird tbh.