Cooling system problems?

[The_Laird]

Yes, that's a possibility. Just wondered though, are thermostats like they always were, or has the technology moved on since the 1970s?

I'm monitoring it now and just letting it do its own thing a bit (rather than panicking and turning the heating up high!).

I do around 35 miles each way to and from work; 22% on A&B roads; 28% on dual carriageway and 50% on motorways (although that isn't always quick!). And pretty much in that order going and the reverse order coming home.

In the morning, it gets up to 90C pretty quickly and stays there until I start the run of traffic lights through Dumbarton. Then it starts to rise. It falls at higher speeds on the motorway and dual carriageway, and rises again when I get stuck in slower traffic.

But it's not risen above the section marker above 90 (whatever that represents - what is the point of these if you don't know what they mean?) so far, so I'm not overly concerned yet.

[moltuae]

Assuming 90 means OK, I guess the increments are:

Be concerned
Get worried
Panic
Too late, engine fubar-ed.

I don't know to be honest, I can make any sense of them either. I suppose you'd need to heat the sensor up and compare the gauge with VCDS readings to find out how they relate to coolant temperature.


As far as I know, thermostats still rely on the mechanical expanding wax principle. I suppose there's no real benefit in replacing them with anything more sophisticated.

I think I'd probably try a coolant flush and refill to clean out any gunk.

[ainarssems]

It's possible the Radweld is responsible if that's the case, especially if it started happening just after that.

That's my opinion as well. Is the interior heater working OK or does it have reduced output as well?

Just wondered though, are thermostats like they always were, or has the technology moved on since the 1970s

Pretty much the same, there were couple of cars that used sensors and electric valves but it never took off, possibly due to higher cost and complexity, maybe even reliability.

But it's not risen above the section marker above 90 (whatever that represents - what is the point of these if you don't know what they mean?)

Pressurised cooling systems are good to 120C so that's what the red marker is for. If you divide markers between 90C and 120C you will find the value increment for each marker.

[mattylondon]

Additional to the above suggestions, have you checked the radiator fan thermo-switch?

[The_Laird]

Answers to the above:

Yes, the internal heater seems to be working OK and the garage checked the fan came on at the right temperature.

I think I'll give it a few days and, if the problem continues, take it back for a flush and, if necessary, a new radiator.

I don't suppose a used radiator is a good investment, and I'd guess that an Audi one would be silly money, so recommendations for a good source of a new one would be very welcome.

[David's8]

Originally Posted by The_Laird

Answers to the above:

Yes, the internal heater seems to be working OK and the garage checked the fan came on at the right temperature.

I think I'll give it a few days and, if the problem continues, take it back for a flush and, if necessary, a new radiator.

I don't suppose a used radiator is a good investment, and I'd guess that an Audi one would be silly money, so recommendations for a good source of a new one would be very welcome.

Since I had my overheating issue with the failed thermostat, mine has been as steady at 90 as it was previously. As i noticed when nursing the car home after the overheating, the electric fan cuts in at around 95/97deg so it seems like your fan is doing its stuff which means that there is something else at work here such as restricted flow. Have you had VCDS connected when the overheating has occurred? I noticed when monitoring mine (with the faulty 'stat) the temp display on 2 occasions showed a rise to 95 and then stopped whilst VCDS continued to show a steady rise beyond that to 100deg before I switched off - even tho' I suspect that the two things are monitoring the same sensor It would be useful to get confirmation that the display is actually showing what VCDS sees.

[Architex_mA8tey]

Originally Posted by The_Laird

I do around 35 miles each way to and from work; 22% on A&B roads; 28% on dual carriageway and 50% on motorways

Do you deal with a lot of stats at work by any chance Jim?

[The_Laird]

Originally Posted by Architex_mA8tey

Do you deal with a lot of stats at work by any chance Jim?

What makes you think that?

[The_Laird]

Originally Posted by ainarssems

If you divide markers between 90C and 120C you will find the value increment for each marker.

Surely not! If you assume the 120 mark is the one before the red one (although it's not that clear) then the marks are as follows:
50 (marked on the dial)
63.33
76.66
90 (marked on the dial)
97.5
105
112.5
120 (marked on dial)

Given that the marks aren't equidistant, why would they choose such daft values to mark up? And why make the interval before 90 at 13.33 and afterwards 7.5?

[IT]

Originally Posted by Architex_mA8tey

Do you deal with a lot of stats at work by any chance Jim?

haha. I too noted the overly detailed accuracy on his reporting...