Hi Guys,

I am looking for some advice here about an on going problem with my 1998 A4 1.9 TDI.

About 6 weeks ago I had the head gasget blow. This caused the oil to mix with the coolant, and gave me a froffy, orange foam in the cooling system, which then spent about 15 mins pouring out of the coolant reservoir via the cap/overflow.

I had the head gasget repaired, (new gasget/skimmed etc) and also had a new thermostat fitted. During the head gasget being fixed, the garage called me to say that the Radiator was also leaking. We agreed to try fixing it with some sealer instead of replacing it to keep the cost down.

I got my car back, and all was well for a couple of weeks, until the coolant started to disappear. At first, only a small amount, then it got worse as time went on. small amount being about 1/4th a litre, and worst so far was approx 10l required over 50 miles.

So, assuming the radiator was the problem, I then had this replaced.

I got my car back, and all was good again for about 2-3 days, and then coolant started to disappear again in the same manor, started off with just a top up now and then, and now results in needing a lot of fluid daily.

So, the car went back to the garage again, where they pressure tested the cooling system. It passed the test. They then re-tested the system with the engine hot, again it passed. so, we know that the radiator / reservoir etc is not leaking.

At this point in time, we also replaced the cap on the reservoir assuming it was letting fluids pass.

Today, whilst testing the car (60 mile round trip) i also lost coolant. in the first 30 miles, driving approx no more than 2000rpm it lost approx 1/2 litre.

The journey home I took some faster roads, and took the car up to 2500rpm / 2700rpm where possible. After a while I noticed the temperature guage creap up above its usual 90. I pulled over, expecting to find no coolant in the system thus the overheat. However, the reservoir was at least 3/4 full. So, with this in mind... I am wondering if the problem is the water pump. The car quickly returned to normal temp, 90 and I was able to drive it home, keeping the RPM reasonably low. It did not overheat again.

I am aware that the pump in the A4 is simply an impeller. Could it be that this is damaged and thus not able to pump the hot water from the engine. The water in the engine is then boiling, causing excess pressure and coolant to escape through the reservoir cap?

As a side note to the story which I am sure will fit into it somewhere is the heater. About 4 weeks before the head gasget died, the heater was not able to produce anywhere near its usual level of heat. This got better after the car was repaired, but nowhere near where it should be. I did read online that somebody who was having similar symptoms to myself foudn the problem caused by the water pump not having enough pressure to get the water into the heater block effeciently... does this sound right, or is it misguided guess work?

Ideally I am looking for peoples "best guesses" as to what the problem is likley to be?

Thanks in advance for any replies,

Alec.