a4 overheating problems

[tottie24]

A4 b5 1.8 APT engine.
while driving the car it heats up quite quickly and then goes on to overheat if i go above 30 mph or so. if i crank up the heating to max the gauge slowly returns to 90. t stat changed less than 6 mths ago waterpump just changed and its still overheating. radiator is cold at running temp and while over hot, top rad hose hot and bottom cold. also getting plenty of hot air from vents, viscous fan seems to work as normal and elec fan doesnt come on except when ac is turned on?
thinking of trying coolant temp sensor. also should i be able to see coolant returning to expansion tank as it is running?
im at wits end and have already sunk £££ into this car.
thanks.

[yugo]

coolant temp sensor or thermostat stuck close.. if have a vag-com you can check the engine coolant temp, if it is very diferent from what shows your temp gauge then replace cts..

[mikeya4]

if the rad is cold but the top hose is hot, it sounds like a blocked rad, i would try and flush the rad through and see what happens

[Chris_Yeovil]

Hi, I'm new to this forum. I've been having a similar problem (2000 1.9 TDI) for a few months now: car is fine around town but when I put my foot down even a tiny bit, it overheats. I have replaced the viscous coupling on the main cooling fan but this made no difference. I've read elsewhere in this forum that the electric fan is only required to draw air across A/C rad. This seems a little unlikely because the electric fan is fed through a resistor pack having three resistors: low speed - to draw air across the A/C rad; And two other speeds - for extra engine cooling maybe... My point here is that your electric fan is working at idle (as it should), but if the resistor pack is shot you won't get the extra cooling it provides when the engine coolant gets too hot. I haven't replaced my resistor pack yet because I've just replaced my electric fan - which wasn't spinning up under any circumstances. Turns out that wasn't the problem and I'm not quite ready to make another expensive diagnostic error. I hope this is of some use to you. Please let me know how it works out. All the best.

[mikeya4]

first easy check is to check the hoses, top and bottom to check the water is going through the rad, mine was overheating on a run because the rad was completely blocked, top hose was hot plus bottom hose was cold= water not circulating through rad