Overheating mk4 1.6 16v AUS 145k

**Tallulah** · 09-04-2017,04:45 PM

I have a problem with my car. I was driving down the motorway the other day and suddenly my coolant temperature icon flashed red and I realised my temp gauge was all the way up. I pulled over and popped the bonnet and let it cool down whilst I called the RAC. They came and had a look and the bottom hose was cold so he thought faulty thermostat. He took it out so I could go on my way, topped me up with water and that was that. I have now had the thermostat replaced but the bottom hose is still not getting hot and the car is still overheating?!
I had the water pump replaced about 18 months ago to the new one with the metal impeller so I'm pretty sure it's not that. I had a top engine rebuild a few years ago so pretty sure it's not Head related. Anyone got any ideas??
I should also mention that previous to this problem occuring, my temperature gauge had not been working correctly, rarely getting up to 90 but I have never ever seen it over 90 like it is now.

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**niall campbell** · 09-04-2017,05:36 PM

Change the Coolant Temp Sender unit with a genuine VW one, it wont cost much more to buy one from VW

Doesn't sound as its much more than that, but report back & let us know how you get on

**Tallulah** · 09-04-2017,05:47 PM

Thanks I will try this, any idea why the bottom hose isn't getting hot now it has the new thermostat fitted?? Could there be an air lock somewhere or a blockage in the radiator? It does appear that it is actually overheating, not just a faulty gauge?

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**niall campbell** · 09-04-2017,06:20 PM

well it could be the radiator core is blocked with rust and not flowing as freely as it should, you would need to take it off and test it with a flow meter, just depends how good the topping up has been with antifreeze over the years

or

the new water pump

or

the new thermostat

Its just you said that the temp guage hardly ever went to 90 before ..................................... leading to a suspect CTS

Were the fan or fans running when the car was hot ??

**Crasher** · 09-04-2017,10:57 PM

You fitted a new thermostat insert but did not notice that the problem was the plastic bridge the thermostat operates on inside the cover, not the thermostat itself, the top blows off and the operating rod just goes through it. This is why it is best to fit a complete new housing.

The top cover is VW part number 032 121 121 J

**Tallulah** · 23-04-2017,04:21 PM

You were correct, it was broken inside! Car all fixed now, thanks for all the advice

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**Tallulah** · 02-06-2017,08:58 AM

Was driving along the motorway and noticed that the temp gauge was halfway between 0 and 90? Then the traffic slowed slightly and it went up to 90 but then when I stopped at a junction it started to fall again, when I got into town it slowly went back up to 90 and stayed there. It never went over 90 at any time. Is that normal??

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**Crasher** · 02-06-2017,10:06 AM

It should go upto 90 fairly quickly in this weather and never move not matter what. How did you repair the broken thermostat unit?

**Tallulah** · 02-06-2017,10:21 AM

Originally Posted by Crasher

It should go upto 90 fairly quickly in this weather and never move not matter what. How did you repair the broken thermostat unit?

Removed the pipe and let the coolant drain, removed the thermostat and the housing, which you correctly pointed out was broken, put the new housing and thermostat in and then refilled with coolant. We didn't check the temperature switch? Could it be this?

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**Crasher** · 02-06-2017,02:22 PM

It could be a faulty thermostat, bad assembly or a faulty sensor, this is why I said it is better to fit a complete new housing 032 121 111 BA as it comes, complete

Circoli Thermostat