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dppowell
03-12-2006, 04:18 PM
I have just purchased a 2.8 V6 Quattro A4 and on the first run home it turned out it had no water in it at all, so it massively overheated.

Its now been topped up, but...

Now it is not overheating (per the dashboard anyway) but if I loosen the water cap after a run out in the car it "boils over / steams" etc. Should I be running the car with a tight cap or a slightly loosened cap?

Any help greatly appreciated.

Cheers
David

Marc97
03-12-2006, 11:54 PM
The first words that spring to mind are Uh oh, glad its not mine.
Sounds like you maybe have a head/head gasket problem which is allowing cylinder pressure back into the cooling system.

There are some tests that can be done, with the cap screwed tight, start the car from cold, run for a few minutes and while it is still cold, check the pressure in the top radiator hose by squeezing it. If it is rock hard, you may need to have the heads removed for inspection and new gaskets fitted.
It also might just be airlocked. This can be fixed by putting the car in such a position where a bleed screw or the water cap is at the highest point of the engine and such that it allows the water to run away from the cap. This can be done with a trolley jack so if the filler cap is at the bulkhead, jack up the rear of the car, if its at the front, jack up the front of the car.
With the car in position, run the engine with the cap off, making sure it is full with water and massage the top and bottom hoses, you should see bubbles coming out of the header tank.
I hope thats all it is, just air but I should warn you it might get expensive.

Good luck,

Marc.

VW Techniker
04-12-2006, 01:05 AM
I have just purchased a 2.8 V6 Quattro A4 and on the first run home it turned out it had no water in it at all, so it massively overheated.

Its now been topped up, but...

Now it is not overheating (per the dashboard anyway) but if I loosen the water cap after a run out in the car it "boils over / steams" etc. Should I be running the car with a tight cap or a slightly loosened cap?

Any help greatly appreciated.

Cheers
David

Hi David

The dreaded V6... not one of VAG's greatest engines. They do suffer with water pump problems, but that would cause it to overheat all the time. They are a pig to bleed manually; at main dealers we used to use a filling machine to eliminate air locks. They do have a bleed valve located at the back of the engine on AC models and non AC it is under the plastic bulkhead cover. Fill the expansion tank with the engine OFF & COLD then open the valve and let it flow for a while. Then start engine and let it run, when it flows quickly from the valve its time do tighten it (Dont let the engine get to hot, this should not take more than 5 minutes). Then this is the secret... Push the top hose down as far as it will go, top up the antifreeze (Right to the top) with the engine running at aprox 2500 rpm and screw on the lid... Then just leave it to do its stuff, the thermostat must open at least three times for all the air to clear. Then switch off the car and leave it to cool down properly (over night if you can) then open the lid, check level and top up if necessary... Thats it, your done

Good luck
Robin