S2 ABY Over heating at idle

[Pauliusb2]

I had same problem with my a6 1.8t when i rebuild the head, was same issue as yours and no one could find a problem and everyone was blaming me doing the job on the head!i work for motorfactor and fitted all premium quallity parts like Gates belts ina tensioners and gates thermostat.and after around 2 months testing all different things on the car including gas leak test.i come up with idea.i bought a genuine thermostat from audi which was 5£ more than the gates one,i put the thermostat on the ground and pour boiling water on it and what i saw was very strange,when i pour water on Gates thermostat the thermostat took like 10 seconds for it to open,then i tested the genuine audi thermostat and it opened in about 2-3 seconds,and the audi thermostat had alot thicker spring on it.So i fitted the audi thermostat and since i done 5000 miles inc. 24h drive through europe and never since the gauge was higher then 90. I think your problem is thermostat buddy

[rfsteel]

Thanks for all the response guys.

I've been out and purchased an IR thermometer and got the following results;












So it looks like the coolant is reaching the right places, the only thing of concern was this on the main rad;


So looks like the main rad had an issue, off to check the after run pump now.

[A80Avant]

My bet is the main rad as well

[rfsteel]

Having had a look around the after run pump, it looks like this is a source of another leak;

[mike74]

can't see pictures
you can bypass the after run pump to stop the leak in the short term...will hopefully eliminate the overheating issue

[Thecrispynoodle]

In my experience (the AAN at least) these engines run noticeably hot if they can't maintain coolant pressure, as the result of even a very small leak. I was weeping coolant very very slowly from the turbo return hose and the rad fan was kicking in within seconds of me stopping the car. Now that's fixed it takes several minutes to hit rad thermoswitch temps at a standstill.

[mike74]

^^^ agree

[vonbeck]

i had after run pump trouble just made a bypass out of a copper 90 degree bend with a 2" tail soldered on each end

[bartieke210]

Thanks for all the response guys.

I've been out and purchased an IR thermometer and got the following results;



So looks like the main rad had an issue, off to check the after run pump now.

Your main rad is blocked. Had the same problem. This is the coolant hose that runs to de underside of the rad. There sits also the thermoswitch for the fan. With 80 degrees the fan will not turn on. The temp on the upperside of the rad is 98 degrees. But this does not reaches the thermoswitch. So the thermoswitch sees just 80 degrees. This is because there is no flow through the rad. The flow goes only through the auxilary rad. That seems enough to cool it down in driving condition in normal weather.

[B5NUT]

I know this is an old thread but did you resolve the issue in the end? My S2 also likes to run hot when idle. I've just changed the thermostat for a genuine Audi one and it's still running hot. I would say gauge gets to around 100 and the fan only appears to kick in when you switch the engine off and it comes on immediately.

The main rad looks in very good condition, Checking the car over with an IR thermometer the aux rad does get a lot hotter than the main raid. Could I have a flow issue with the main rad.

[Bowie69]

At 100C it is not overheating, thats the first thing to note.

Second, the fan will run after ignition switch off because the under bonnet temps are too high -nothing to do with the radiator, or engine temp, so this is quite normal.

If the fan NEVER kicks in when running, look at the fan switch in the bottom of the radiator, quite possibly failed, as the fan does work (see above!).

If you suspect a blockage, give the system a flush, it is cheap to do!

Mostly, remember it is not overheating until you a) get a warning on the dash b) See steam pouring from under the bonnet.

[Tractor Dave]

Your fan should be coming on for a bit and off periodically if left idling. Have you tested the switch at bottom of radiator? The wires there are prone to corrosion especially if there is no undertray.

[B5NUT]

Thanks I will take a look at the wires and the connector, but I do not see the fan coming on at all when the temp shows around 100 on the gauge.

Ok so wrists slapped on the over heating statement. All my Audi's over the last 22 years including my 1996 A4 have been at 90 when running and at idle, so I'm not used to to seeing these higher temp on the gauge.

When I got my S2 a few weeks ago the car the car was not getting to temp while driving it on the motorway, it was around 70. Also the coolant looked more like rusty water, and the coolant tank had lots rusty sludge in. So I've replaced the thermostat with a genuine Audi part form TPS, new coolant tank and as best I can flushed the system out. However some of that rusty sludge could be blocking the main rad so it may be worth replacing?

[B5NUT]

Been out and check the bottom connecter on the rad, it looks in good condition and so does the plug, however this time when I plugged it back in I gave it a bit more wiggle and I heard a click noise! So it may have not been plugged in fully..

Also scanned the car and I do have a fault code on the engine about the coolant temp sensor. I will look to replace this
00522 - Engine Coolant Temperature Sensor (G62)
29-10 - Short to Ground - Intermittent

[Tractor Dave]

Clear the codes and try again now the sensor is plugged in
Also run up to temp and fan should kick in.
I recently used a cleaning agent. Put your old reservoir back on when you do this as a lot of crud will circulate. Then flush twice before new pink antifreeze.