Hi All,

I am new to this site and to Audi in general having recently bought a 2000 A6 2.8 Quattro.

I unfortunately bought a huge problem and am having some problems diagnosing the issue.

The car came with a cracked coolant tank which has since been replaced.

The engine was overheating when I bought the car which I thought was due to it not being able to retain any coolant.

After replace the coolant tank the engine was still overheating and that was when I realise that the AC fan wasn't spinning.

Ended up replacing the engine cooling fan switch and the radiator fan control unit but neither worked.

Ended up just recharging the AC and now the AC fan spins.

However, the AC will blow cool air for a minute but after that it will go hot and the AC hose become very hot.

The AC fan will spin and I can see/hear the AC clutch engage and disengage. But the fan does not increase in speed and the engine still overheats.

Any help in diagnosing the issue here would be greatly appreciated.

I can keep replacing stuff but I seem to be stumbling onto fixes rather than have any of the replacements actually fix anything.

I have also replace the AC Relays and fan relays.

My next step was going to be to replace the AC fan. But I was hoping for some insight as to whether it would even begin to fix the problem.

Thanks in Advance...

 

Okay.

No takers soo far..

Here are some updates. Here are some more things I found out.

1. Radiator gets hot after running for a while.
2. Fan clutch is gone. I can stop the fan with a roll of newspaper very easily.
3. Interesting point here is that the little water hoses that go to the coolant tank get hot. However, the large hose that goes from what I think is the water pump to the radiator does not get as hot. It was a tepid warm at most. Water temperature on the gauge is over half.

Anyone can help?

Is it the water pump?

Which direction does the water flow through the radiator?

Could it be a clogged radiator?

That that hose carry coolant from or to the engine block?

 

The plastic cracked coolant reservoir is common problem. Here's coolant circuit diagram for the 2.8 to help you out. Sorry I can't help you out more, but I haven't worked with the fan & relays before.

 

Hi,

Thanks for that. It will help me heaps in getting to the bottom of the problem. I will post back here once its been sorted.

 

Okay. Still no luck in finding the issue that is causing the overheating.

I have replaced the fan clutch and not the secondary fan also comes on and spins fast when the AC is on.

Added coolant and bled the system of air.

Seems to run fine. But after about 20 minutes I notice a lot of bubbles in the coolant tank and the water temp rises very quickly. It will rise from half to almost max in about 5 minutes.

Once it is hot I try to vent and there is a lot of air again.

There is no heat in the car. So not sure if the heater core is clogged. Will be trying to flush that and have a look.

Radiator is not clogged. Fan clutch is brand new. But engine will still overheat after about 25 mins and no matter how much I vent the air pockets There is still always air again.

I thought there might be a little bit of a head gasket leak and tried some blue devil but no difference.

If there is a leak in the head gasket wouldnt the air/gas start immediately and not just when the water starts boiling.

Could it be water pump not moving water? Or thermostat stuck shut?

Any help please? Spending heaps of parts that don't seem to make any difference to fixing the problem.

Next on the list is to confirm the heater core is not blocked. and if that doesn't solve it... timing belt, thermostat and water pump.

 

Based on the fact that you're seeing coolant bubble / boil and having to add coolant, there is no flow from your coolant system. The liquid is sitting stagnant and is boiling and evaporating through the overflow port in the expansion tank. This can be due to a thermostat stuck closed, or a water pump that has separated from the impellers.

 

Being that it's a recent purchase, do you have any records confirming whether or not the timing belt service was completed?

 

Hi

Thanks for the answers. Unfortunately no records it has 180k miles on it.

I guess it makes sense that it is the water pump or thermostat or both. I guess I will have to give it a try.

Thanks again. I will update hen I have changed the mining belt, water pump etc