Audi A3 Water Temperature

[Stu_UK]

I appreciate that this might be little more than paranoia on my part but I've just observed something odd with the water temperature on my A3 ('99 1.8T factory standard!) that I've never seen before in a year of ownership...

I was nearing the end of a brief journey from home to work and back (i'd say less than 20 miles round-trip, half-hour total journey time; mainly motorway) whereby I became practically obssessed by the behavior of my water temperature gauge: In the last few miles of my journey, just as I was leaving the motorway I saw the temperature needle drop to below 85°C; it's normally between 85°C & 90°C. As I made my way through a couple of 40mph roads the temperature began dropping further still where it bottomed out at about 79°C - I have never seen it drop that low at the tail end of a good run! The outside temperature was +9°C so it wasn't exactly freezing either.

When I finally pulled up outside my flat I just sat at idle for a bit and watched as the temperature gauge made its slow crawl back up to 90°C.
I seldom hear the fan kick in (it's pretty quiet!) so I'm afraid I can't tell you if that was stuck on or not. The moment I arrived back at the flat I got out and put my ear to the grill; the fan definitely wasn't stuck on at that point!

Can anyone please tell me: Have I just witnessed an early warning sign to something that may grow into a complete ballache? Would the in-car computer warn me of anything potentially catastrophic??

Last year I had serious cooling issues with a Peugeot 306 D-Turbo which ultimately resulted in a trashed engine in a shell of a car which ultimately I had to sell for a miserable £50! (hence the paranoia!)


Thanks in advance for any advice you can offer!

[ed'sA3-1.8THK]

there are (2) separate sets of components involved:

(A) cooling system "thermostat" and "water pump"

thermostat may by sticking / not moving freely / suddenly opening/closing

change thermostat immediately - this must be eliminated to troubleshoot "others" - ENGINE MUST BE STONE COLD - change o-ring as well

water pump has resin impellar which gradually crumbles with age - driven by timing belt - always replace water pump when replacing timing belt - there is german water pump with iron impellar - prefered replacement

(B) "control module" of electric fan(s) and "temperature sensor" (lower left side of radiator, on inside/engine bay side) of electric fan(s)

the fan control module is a known issue with older A3 1.8T's - this should always be changed together with fan temperature sensor - this gradual drifting of sensor combined with light welding/burning of control module contacts will result in irregular fan operation and prolonged fan operation - but not necessarily continuous fan operation at beginning of failure period

I assume NO coolant leaks and normal coolant appearance in reservior sphere (pinkish/redish/purplish smooth liquid - NO solid material)

Begin with engine water thermostat now

(1) additional item - look at back end of cylinder head near air filter box & battery box - looking down you will see hose(s) from radiator to cylinder head - there will be (1) or (2) electrical connectors to water temp sensors - if you still have "black" top sensor (4-pin) and not "GREEN" top sensor - immediately change to "GREEN" top sensor - requires green sensor/o-ring/resin "c" clip - ONLY WHEN ENGINE IS STONE COLD - DO NOT open reservior - only small amount of coolant will leak out - be certain to lift out old o-ring

I need to add that a water temp guage w/pointer abnormal movements occasionally (but not always) indicates a corrupted dash instrument cluster control chip) - keep in mind for future

start w/ thermostat (do not fit lower opening temp aftermarket / fuel mileage will really suffer) and confirm "GREEN" top sensor cold start/combi w/guage sensor is fitted already - if not immediately fit

after doing these (2) things, you can determine condition of fan control module...

[Stu_UK]

Ed,

Thanks for taking the time to compile this; at least I have a direction to go now!
If something arises from this I'll post it here!

[BVR.Automotive]

Sounds like the waterpump to me, very much doubt it will be thermostat.

Remove and check waterpump

Dave

[ed'sA3-1.8THK]

given a 10yr old 1.8T engine, it is now time to change original thermostat, very likely no longer opening at correct temp - usually drifts to lower opening temp delaying eng warm-up

this is practical & inexpensive routine maintainance

this also ensures that the water pump impellar failure/resin-breaking-apart can be accurately diagnosed - important because this is significant engine repair cost issue - at 10 yrs this will mean timing belt, tensioner pully, pully bolt, hydraulics AND water pump / o-ring and if necessay crankshaft front oil seal & crank belt sprocket & keyway & sprocket bolt

the water pump is not rebuildable and should be replaced with alternative recognized german iron impellar replacement water pump

remember that water pump shaft serves as pivot for timing belt and is critical timing belt component - NO china pumps!

and at 10yrs thermostat replacement is an accepted practice