cliffcoggin

That's unfortunate, but there is a limit to what can be diagnosed through the necessarily brief written descriptions in a forum like this. This leaves you little choice but to get a proper diagnosis done by a competent mechanic, unless you enjoy throwing good money after bad by renewing one component after another.

Almost certainly the problem is an air lock created when the thermostat was changed. The coolant system should have been vented by the mechanic who did the work, so I suggest you take it back and get him to finish the job properly as it can be a devil of a job to do yourself.

Hello Balzout. I doubt that it is a worn wheel bearing, the sound is wrong and would be unaffected by clutch operation. However a wheel bearing can be tested by jacking it off the ground and turning the wheel by hand. A worn bearing will make a low rumbling sound. You may even be able to feel looseness in the bearing if you rock the wheel left/right and top/bottom. Don't be misled by any scraping or scuffing sound from the brake discs. I speculate that there might be vibration of the clutch hydraulic pipe against some part of the steering linkage. That would explain why the noise is affected by turning and clutch operation. My car is an automatic so I don't know the route of the pipe, hence my idea could be sheer nonsense. Nevertheless it would be worth looking at the pipe route around the engine bay, rattling it in search of loose clips. Check too that the steering rack is firmly mounted by getting another person to move the steering wheel to and fro while you look at the rack.

Steve. If you can justify the expense of an accurate diagnostic machine, which I can not on a 14 year old car that rarely has problems, then I have no doubt that is the best way to go. The problems I see on this forum are cheap inaccurate readers, used by owners with little or no knowledge of mechanics, which induce them to waste a lot of money on unnecessary parts. Cliff.

In regard to general non-specific warnings like ESP I take the car to an independent Audi specialist. Its expensive, but cheaper than buying a succession of new parts in the hope that one might resolve the problem. If the warning light is specific (such as "low coolant level") or there are no warning lights at all, I'll first turn to my experience of diagnosing and repairing my own cars for the last 53 years before deciding whether I can carry out the repair myself or take it to aforesaid Audi garage. Working without diagnostic equipment years ago is what I meant by being old school.

The point about old batteries is not so much their remaining capacity in terms of ampere-hours; it is more to do with internal faults that can interfere with the car's ECU. I am no electrician so I can not explain it in any more detail, but I am aware that batteries can suffer internal short circuits, sulphating of the electrodes in lead/acid cells, sediment at the bottom, and other faults that are not apparent to the ordinary user without special test equipment. Can you get the battery tested by an auto electrician? When I last had a new battery fitted as a result of similar false warning lights, loss of turbo, and loss of cruise control, I was told it had to be "coded" to the car. Being a natural cynic, that phrase instantly made me suspicious that I was being told BS. Even though the new battery cured all the problems with the car I still don't know whether to believe this coding story.

You mentioned at the start that you had a faulty battery which you dealt with. Did you fit a new battery or a secondhand one? Old batteries can cause a variety of apparently unrelated faults even when the alternator is putting out a good charge.

Good point about scrap yard absences. I too am sceptical of error code readers. I see many examples of false diagnoses on this forum, though I am too old school to have personal experience of them.

Rob. In regard to question 1, the first press of the key fob button unlocks the driver's door only, a second press within five seconds of the first unlocks all the other doors.

None of us doubt how easy it is to change that switch. The important question is whether you simply struck lucky in choosing that option from the many possible causes of an ESP warning, or did you know it to be a particular weak point of the A3?

Ryan. Colourless fumes or slightly grey smoke would be just an exhaust leak, but white smoke suggests coolant is mixed with exhaust fumes. Is the water level dropping? I seem to recall that the EGR (exhaust gas recirculation) valve is water cooled, which might be the source. Not sure on this point.

Getting rid of the warnings and resetting the codes is pointless unless you cure the fault that is causing them. If the yellow ESP light has been on since you bought the car that is the first thing to investigate. It is not something that can be diagnosed on a forum unfortunately because so many circuits are linked to it. You need professional help to solve the problem.

It's impossible to guess with such meagre information. See this for suggestions: http://www.auditech.org/acont-654.html

Fair enough. It does seem that LEDs are brighter.

I am curious to know why you want to do that?

I have feeling that the discussion of viscosities etc. is a red herring in this instance, and that there is an underlying problem that has not been solved. Let me explain. The oil pump should be capable of creating much more pressure than is required by the engine in order that the pressure is adequate at idling speed, no matter what viscosity of oil is used, any excess pressure as the engine speed rises being bled off by a pressure relief valve to maintain a more or less constant pressure in the oil galleries. In this case the pressure is not high enough to prevent the warning light showing, so the question becomes why that should be. The possibilities that occur to me are: [1] The oil pump is worn. [2] The pressure relief valve is faulty. [3] The engine bearings are worn. [4] The pressure switch is faulty. [5] The pump is sucking in air. Unless anybody can add to that list, or disprove my logic, the problem must be one of those five things. I know that some of those parts have been renewed, but even new parts can be faulty or incorrect for that particular vehicle. Furthermore I see no investigation reported yet of items [3] and [5]. What say you chaps?

Not necessarily all the time, however smoking is always worse when the engine is working hard. A dense cloud of black smoke is not the result of removing the EGR alone, something else is wrong. Perhaps the injectors, perhaps engine wear, perhaps the remapping, but whatever the cause its sounds as if it will fail an MOT because of the emissions so you need to resolve it. My natural cynicism would make me suspicious of any engine that had been modified in the way yours has. I suggest you get it tested and hope the solution is not expensive.

Blue smoke is a sign of oil burning, usually because the rings/bores are worn. Does it smoke under hard acceleration? Erratic idling may be part of the same problem if the engine is clapped out and has lost compression, or it may be unrelated.

Fair enough, it must be something else. The advice from your garage is utter nonsense. Soot can not be created or deposited in a non running engine.

A faulty battery can cause those sort of problems, even if the alternator is putting out a good current. Is the engine turning slowly when cranking the starter? Do you have to keep the battery topped up on a mains charger? Is the acid level up to the mark?

James. If these 13-15 year old cars you are looking at are still running I'd say they have all proven their reliability. How long are you expecting your purchase to keep going? Personally I can vouch for my own 2007 2.0 TDI, but then I have zero experience of other engines for comparison, so don't rely on my opinion.

Good day Kevin. Bearing in mind that I know nothing about audio, the only the thing I can imagine that would interfere with radio but not disc player would be the aerial. Perhaps check the connection at the back of the set to start with.

I think I recall somebody solving that problem a year or two back. Have you looked through old posts of this forum?

For clarification Martin, is the juddering when you are slipping the clutch, during take off for example, or when it is fully engaged? If the former I agree with Gareth; if the latter something else is wrong.

What engine? What fuel? What transmission? Give us a clue Martin.