I have a 1998 1.6 Sport A3 and for about 4 months now it has been losing coolant at a very slow rate. By that, I mean that if I fill the coolant up to the Max marker it takes 6-8 weeks to drop below the minimum marker and prompt me to top it up.

I just assumed that it was a tiny leak somewhere and decided to get it investigated at my next service but the other day I removed the oil filler cap to discover a yellow coating on the underside of the cap and around the neck of the hole that you pour new oil into.

I immediately started to put 2 and 2 together and draw the conclusion that coolant loss plus yellow emulsion in the filler cap means head gasket is gone but my garage, who I called the next day, insist otherwise. They said that the yellow coating that I can see (which is about 2mm thick and pretty much evenly coats the bottom of the cap and the neck down towards the rocker cover) is common in modern engines and is simply the result of condensation. If I remove the dipstick, there is no sign of the yellow froth on it.

Of late (for abut the last 2 months),my car has been used Monday-Friday for a commute to my new job. This is about 10 miles in each direction so the engine is just about getting up to temperature as I arrive at work but rarely runs for a long period at normal operating temperatures.

Now, I'm no expert but I can't help but think that the signs don't look good. The only thing that makes me think it may not be the head gasket is that the rate of losing coolant hasn't increased - more mechanically minded people than I have told me that once it goes it gets progressively worse as the gases pass through the gap.

Also, the garage said that this particular model engine is rarely subject to head gasket failures so the stats are suggesting that the likelihood that that is my problem is low.

The only other things worth mentioning in relation to this is that when I first start the car on the cold mornings recently it seems to only run on 3 cylinders for 5-10 seconds - a single gentle blip of the accelerator irons it out. I was hoping to get his sorted, assuming it is likely leads or plugs, at my next service too.

Does anyone have any anecdotal experience or thoughts on what this might be - am I worrying about nothing? Am I about to be hit for a 4 figure bill? Should I get rid of the car now while the going is still good?

Thanks in advance.

 

I had much the same problem (1997 A3 1.6). It did eventually require head gasket replacement. My thoughts:

- The yellow froth *is* due to normal condensation, especially as your daily drive isn't long enough to really heat the engine up. If you go on a long motorway drive you'll find that the yellow froth disappears.

- My car was losing coolant very slowly and also running rough for the first few seconds after starting. In my case this was almost certainly due to the head gasket leaking a little overnight as it cooled and contracted, letting some coolant into one of the cylinders. As with yours, it would sort itself out fairly quickly as the coolant was pushed out of the cylinder. It was also possible sometimes to see more steam than normal in the exhaust. The rate of coolant loss didn't really increase though.

- Eventually the dealer replaced the head gasket and skimmed the cylinder head before refitting everything. I haven't had any problems since.

So, it sounds like the big bill might be on the way - not quite 4 figures in my case but not far off! On the plus side, you get a fairly comprehensive engine strip down, check and rebuild, so not all bad.

If you haven't already, get the dealer to pressure test the cooling system and see if anything comes up - it could be the gasket or the head itself. Although in my case pressure testing didn't show any problems - we'd just ended up ruling out everything else!

Hope this helps...

 

Bump - ever find out what the problem was?