Audi Repair: Audi A3 1.6, oil filler cap, audi a3

Question
QUESTION: hi, my 98 R reg Audi a3 1.6s has started sounding rough, it sounds almost as af the exhaust is blowing however the local garage was unable to find a fault with the exhaust. Also there is a caramel coloured gunge under the oil filler cap it was a film but iv just had a look and it looks lumpy now, the car is running fine it starts first time and it doesnt shudder at all ,the noise is only at approx 2k revs can you help???

ANSWER: The build-up under the oil cap is more than likely water/oil emulsion.  This can happen in normal use if the car is used for small distances, and the engine never really gets very hot.  It can also happen if the thermostat is faulty which stops the engine from warming up properly.  If you can tell it is running rough but your local garage cannot find anything, then maybe it is time to go to a less-local garage who can perhaps serve you better...?  Short distance driving will do the same for exhaust systems, they corrode much faster since the condensation is never fully dried up before the engine is shut off again.  This condensation is pretty agressive at corroding through exhausts; typically in the areas of resonators and mufflers.  Is the noise more pronounced when the engine is cold?  Typically if there is a crack in the header or manifold, this will expand when warming up and the noise will be much reduced when the engine is warm.  Let me know,  Jan

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QUESTION: yeah i think ill try a dealer, and no isnt as noisy when its warm i reckon ill get an oil change, possibly an engine flush??? then take it for a long run then see how long, if at all, it takes for the caramel stuff to build up what do you think??? your advice is very much appreciated.

Answer
Engine flush is an option, but the oil change itself will be a good idea anyway; a run for an hour should allow the heat to build up where the water will be extracted from the oil deposits.  I would REALLY warm the engine up before the oil change is done.  The garage should be able to drain the oil while the engine is hot.