2002 2.0 ALT Engine Overheating

[Flyno]

Hi folks, i'm new to the forum so i will try my best to explain this. As title says, i Have a 2002 2.0 petrol alt engine. In the last 5000 miles i have replaced the Thermostat, both temp sensors, coolant flange, water pump (timing belt kit also done). I have bled the system with the coolant cap off, also at the metal bar (alan key) that goes across the top of the engine and at the Heater core. I have hot air and also cold air coming from the system. After a short drive, 20-30 miles the car will overheat. If i turn the heater on to HI at full blast the temp guage will stay at a perfect 90 but as soon as i reduce the heating temp the temp guage will rise and the coolant light will come on. All parts for this car have been bought from the main audi garage where i live and are not OEM parts. The car has only done 125,000 miles and has a full audi service to 100,000 miles and this is the 2nd water pump (first was at 81,000 when t-belt was also done.) I have checked that flow is coming from the top hose into the coolant tank and there is no loss of coolant or oil (head gasket) etc. Can anyone have any idea what else can be the problem, I really love this car but its now becoming a money pit, and, local mechanics and even the Audi dealer just keep saying "it could be this or that" and all have turned out to be just expensive work done for nothing as the problem still persists.. Thanx in advance for any replies and help that you can give..

[kite]

Do the fans cut in when the engine gets hot.

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[Flyno]

Hi kite, thanx for the reply, yes the fans cut in no problem and when i put my had in front of the Rad i can feel the cold air being pushed through the rad. I should also mention that i also flushed the whole cooling system and put in new coolant in January.

[kite]

Sounds like pump failure.

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[Flyno]

Really??? The pump thats in it has only done 4000 miles, its a genuine audi pump too. I have done the top hose of the coolant box and revved the engine and watched the coolant flow from it no problem. Thanx for your replies Kite, its a nightmare that the pump cant be checked without all the labour charges that the mechanics charge for the removal and refitting. £250-£300 labour is a lot considering that the pump is not that old and has only done 4000 miles.,, Again, thanx for taking the time to reply..

[kite]

If the pump was purchased from Audi it will have warranty, if faulty the warranty will cove the cost of the work to replace it.

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[micheal balbrig]

Why not try another thermostat first,or a trial with none.
How did the problem develop.
When it is overheating,is radiator hot all over(care required as fans can come on)
It seems odd that the air flow through small heater is enough to cool the system,maybe main rad has restricted flow.

[Flyno]

Hi Kite, my local Audi dealer told me that if indeed it is the waterpump, they will replace the defective pump but will NOT pay for the labour as they did not put the waterpump in. They are sort of saying that maybe my mechanic done something wrong, even though it was driving perfect for 1000's miles. So i am caught in the middle, all the symptons point to the waterpump but the labour cost in replacing is crazy, considering i already paid to have it done only a couple of thousand miles ago..

[Flyno]

Michael, thank you for your reply, "trial with none", is this even possible, the thermo is incased in a plastic housing with a few hoses coming out of it.

The problem started a few months back when i noticed that when i turned down the heater temperature in the car the engine temp went up. When it gets halfway between the 90 and the 130, the coolant light comes on but the car is not loosing coolant.

I have not touched the radiator, i have just checked that the fan is on and i then put my hand in front of the radiotor and i can feel the air flowing through it. Do you think a clogged radiator might be the problem??? Can this be unclogged or easier just to replace...

The heater matrix seems ok as i can get warm air and cold air working in the cabin, its just when set to any temp below 25-26 the engine overheats even though i have cool air flowing inside..

[micheal balbrig]

Maybe not possible on your model,some have thermostats inside with an o ring seal, anyway it is probably still best to eliminate the smallest items first.

Thermostat,water pump. My thoughts on the main rad was due to the fact that if the matrix is enough to cool system.why is main rad not cooling it.
Also maybe get garage to test coolant for head gasket problem. ( these are my opinions only.non expert)
It seems from other replies that the cooling system needs to be bled thoroughly, possibly many times,and it is suggested to loosen header tank and hold in highest possible position while carrying out bleeding. Some suggest pressure bleeding.