temp problem

[rampagey]

Could any one help me with a temp problem i have with my 1.8 A4 B5
When i am driving normally the car temp gauge doesn`t go above 65 , Is this normal ? and if what could be the problem that is causing my engine not to reach the correct operating temp.

thanks for your time

mark

[audimad]

Thermostat and/or temp sender would be my bet.
Try the 'stat first and see what happens. Around a fiver for the part iirc

[rampagey]

thanks for the advise

[AutoTDI]

Is your cooling fan running continuously?

[A4Chris]

Broken thermostat me thinks. Temp should sit at a steady 90 degrees or thereabouts. Most thermostats fail after 7 or 8 years as a result of temp sensitive wax loosing its thermal properties. Fairly cheap and simple to replace though.

[edihans]

Is your cooling fan running continuously?

My wife's '01 2.0 B5 had the engine temperature gauge not working and also the orange engine management light on.

This morning, I replaced the temperature sensor (£23 @ Eurocarparts). When testing the new sensor, I noticed that the radiator fan switched on immediately after the cold start and the temperature gauge came only really slowly up (took 10 min or so).

Now after a few short trips today, the engine management light no longer lights up, and I just started the car and the fan didn't start.

Could it be that it takes a little time before the engine management system responds to the new sensor? Also, I wonder if AutoTDI's question relates to the symptoms I am describing above?

[RickT]

Tthermostat issue is my guess..

Try doing a search in the B5 section for thermostat, im sure i have read it before in there..

Rick

[edihans]

Hi Rick,
Thanks for your reply.

I drove the car a bit earlier today and where in town the temperature raises to to almost 90 degrees, on the motorway it drops to 60 or so. So in my opinion it points indeed at the thermostat.

I browsed the B5 section. From that I learned that the thermostat sits somewhere down in the enginebay, when you follow the dipstick? Then again, I read as well that it isn't to difficult to replace yourself,. Howver, if it is at the bottom of the enginebay then, given the plastic 'cover' under the enginer, makes it difficult even to get access to it. Or am I missing something here?

[A4Chris]

Thermostat is located in thermostat housing which is on the base of the water pump assembly. Access is therefore from underneath the car. This will require removal of the plastic under engine drip tray (which is fairly straightforward). I am fortunate enough to have a pit in my garage which makes under car access a doddle, but failing this you will need axel stands or wheel ramps to gain access (make sure they are good quality with BS approval).

To get access to the thermostat you will first need to drain the cooling system by removing the expansion tank cap, then disconnecting the radiator bottom hose and removing the drain plug at the base of the water pump. The thermostat is then removed by undoing the two bolts which hold the thermostat housing against the base of the water pump assembly (access to 1 of which is a bit of a headache but perservere with a small spanner and you will get it eventually). Once thermostat housing is removed you will see the thermostat and rubber sealing ring. Remove both.


At this stage, I would recommend flushing the cooling system with clean water by running hosepipe water through the expansion tank and then radiator top pipe in turn until only clear water drains out (of water pump drain plug and radiator bottom hose outlet).

Then insert your new thermostat into the housing (ensuring its the correct way around) and fit a new rubber sealing ring before replacing the thermostat cover and tightening up the two bolts. Replace all hoses and the drain plug on the base of the water pump.

Mix up your new antifreeze to the correct ratio (I use 50% water and 50% antifreeze to gaurd against cold Scottish winters - like we still get them anyway! - but follow manufacturers guidelines). And then prepare to refill the cooling system as follows:-

Undo expansion tank securing bolts without disconnecting any hoses and raise as far out of engine compartment as possible - circa 100mm (to get maximum hydraulic head when refilling - an assistant is handy for holding the tank up as you refill). Undo the inlet pipe to the heater matrix and pull it sufficiently far of its stub to reveal the bleed hole (this is the highest point on the cooling sytem and will therefore allow air to escape as you refill the system). Now you are ready to refill. Slowly and steadily pour the coolent mix into the raised expansion tank. You will hear gurgles etc...as the system slowly refills. Continue pouring until coolant starts to seep out of the bleed hole. Squeeze all hoses to remove any air locks and then add some more coolant until a continuous stream of coolant issues from the bleed hole. Now replace the matrix inlet hose flush against the stub and retighten. Lower the expansion tank and tighten securing bolts. Replace expansion tank lid and start engine. Allow full opertaing temp to be reached, turn off and allow system to cool. Then undo expansion tank and matrix inlet hose as before. Top up level as before (which may have fallen as a result of any air remaining in the system) and then finally replace everything and tighten.

Wash all areas where coolant has wetted in engine bay (as coolant is highly corrosive) and then replace under engine drip cover. Job done!

Thermostat, sealing ring and coolant can all be obtained from GSF. Make sure you get VAG approved coolant and never mix coolant types.

For more detailed step by step instructions, I would recommend a Haynes manual. I find mine invaluable.

Good luck

[edihans]

Hi Chris,

Thanks very much for your very detailed answer.

I'd hoped that replacing a thermostat would be slightly easier.... I need to give it a little think whether to do this myself or not... I have no access to a pit, only axel stands which don't make things any easier.. Then again, I sounds like a like a lot of work... but maybe not completely terribly complicated.

I think I will first get a quote from a local garage anyway. See if it is worth the risk doing it myself ;-)

Thanks again,
Hans.

[A4Chris]

Hi Hans

Is a fairly simple job just a bit long winded and without easy access to underside of the car could be a bit more hastle.

I remember on an old Volvo 740 I once worked on the thermostat was located in one of the radiator hoses. 5 minute job to replace! Why can't audi build things this simply?

Hope you get fixed.

Chris

[edihans]

the thermostat was located in one of the radiator hoses. 5 minute job to replace!

Same here. Only ever did it on my first car (don't tell anybody, a Renault 11:Blush:) and the same there. Top radiator hose, so easy!....

I think I will give it a try myself on the Audi; just need a dry, not to cold weekend day.... The car typically only drives a few miles a day anyway, so I guess it will have to live with it for a short while.

I will keep you posted, Chris. With the detailed description, I am sure I'll manage.... eventually...

Hans.

[bagpipingandy]

My wife's '01 2.0 B5 had the engine temperature gauge not working and also the orange engine management light on.

This morning, I replaced the temperature sensor (£23 @ Eurocarparts). When testing the new sensor, I noticed that the radiator fan switched on immediately after the cold start and the temperature gauge came only really slowly up (took 10 min or so).

Now after a few short trips today, the engine management light no longer lights up, and I just started the car and the fan didn't start.

Could it be that it takes a little time before the engine management system responds to the new sensor? Also, I wonder if AutoTDI's question relates to the symptoms I am describing above?


I have same issue with my 2001 2.0 ALT, changed dual sensor due to low coolant temp readings and now noticed the fan starts up from cold, now thinking either the fan is running all the time or Thermostat,

edihans: Did the change in thermostat fix your temp issues?

Andy

[muddy]

A4Chris has given a good rundown.

Two or three small points as yesterday I changed the thermostat on a '99 1.8 and did another on a 1.8T last year.


There is no need to remove the bottom radiator hose. The drain plug on the pump is sufficient.
Access to the thermostat housing is much improved by removing nut on lower end of snubber stay and loosening socket bolt at top end. Swing stay out of way.
Thermostat removed may well be shut if cold ( older thermostats could stick 'open' giving overcooling) but the problem will be that it is opening too early and you will only see 60-70 degrees on the gauge.

Typically, left on tickover after a run, the gauge may well rise to nearer 90 - but if you drive off it will drop back to 60-odd quite rapidly.
That is the cast-iron sign of a duff thermostat.

Probably the hardest part is holding the new thermostat in place against gravity before you refit the housing !!

You may find that the fat new O-ring just manages to hold it up for long enough.
If not then dry around the seating area with a paper towel, dry the thermostat, put a thin layer of Hylomar around the rim and seating. Wait a minute or two for solvent to go off then stick the 'stat into position, followed by O-ring.