cliffcoggin

Impressive. Hard to believe it only cost $7000.

No, since they presumably have been on the car for a long time so you would have noticed a noise long ago if they were responsible for it. You said, or at least implied, that the hum began recently, and the only other recent changes you have told us of are the front tyres and a CV joint. Constant velocity joints don't hum, but tyres do, so I have no doubt that one or both of the new front tyres is the cause of the noise. Have you tried my suggestion of fitting the spare wheel as a test?

Not too serious, but also not cheap to fix depending on what needs to be renewed.

It's about £1700 Gareth. A considerable sum to lose if I am understanding Riyss properly.

If I understand correctly you have paid a $3000 non refundable deposit so you are committed to buying the car. Is that correct? I suggest you assess whether the total purchase cost plus the cost of necessary repairs is worthwhile, or whether you should abandon the deal and lose $3000. Only you can make that decision in the light of local car values.

So you have a pair of worn out tyres at the back and two unmatched new tyres at the front? It's not worth considering any thing else until you get the tyres sorted out.

It's usually a faulty temperature sensor/control module. Diagnosis with a decent OBD reader should reveal the fault.

You could test the idea if you have a spare wheel with a different brand of tyre. Change each wheel in turn to see if the noise disappears. If you don't have a spare wheel then I guess you either have to live with the noise or spend a lot of money on new tyres that match the old ones. Given that I can not hear the hum you mention I can not comment on it, but in my experience bearing noise is very different to tyre noise.

I can't hear anything untoward, but that's not unusual. Most of the audio recordings sent to the forum supposedly have an odd noise that nobody except the owner can hear. The usual culprit for strange humming noises like you describe is the tyres. Not because they are necessarily defective, but because the tread pattern interacts badly with some road surfaces. Have you changed the tyres recently? Have the roads on your normal routes been resurfaced recently?

Does that mean you were not given the service history by Audi when you purchased it?

Only it it is any good, and you won't know that unless you get it tested, in which case you might as well get the fitted battery tested. Let me emphasise that simple voltage readings from a multimeter will not tell you if the battery is in good condition. A battery can show over 12 volts and yet have internal faults that can interfere with the delicate electronics of the car causing a variety of seemingly unrelated symptoms, one of those symptoms being a lack of error codes on low quality OBD readers. Until you get the battery tested we can not eliminate it as the cause of the starting problem.

Ouch. That's an expensive repair, and very surprising on a 4 year old car. Has it had a hard life, or the oil levels neglected perhaps?

Not necessarily. Instrument clusters are known to suffer failures which may be unrelated to the starting fault, hence my question about cranking from a jump start, and emphasises Magnet's request for detailed information. So far I think we are left with many possibilties that include: starter motor/wiring, ECM fault, defective battery.

Glad to hear the problem is solved and that you don't need yet another starter motor.

That does not answer the question of whether the jump start cranked the engine.

"Engine failure" could mean anything from a broken ignition wire to complete seizure of the engine, and therefore tells us nothing meaningful. I suggest you get the car to a garage to have the problem diagnosed.

Grant. Did the engine turn over when you tried to jump start it? Rather than push the car to a garage why not call out a mobile mechanic and get him to test the battery, which is the most likely problem? 12 volts is too low for a battery in good condition.

I doubt it Richard. Any significant modification usually invalidates the warranty, whether it is related to the problem or not. For your sake I'd be glad to be proved wrong.

I think it safe to say that we shall not hear from Martin again on this topic, so I shall stop following it.

That burnt cable would certainly explain the starting problem. I hope your mechanic is going to renew the cable rather then just wrapping bit of tape around it, and then secure the cable with a clip so that it does not flop around and wear the insulation off.

Thank you. One day somebody will bless you for that information.

Beware of cheap units on Ebay and the like. They sometimes do not come with the appropriate wiring adaptors and connections, so unless you are knowledgable and competent in such things I suggest you get the job done by a professional. There is a company in one of the back streets of Rochester I would recommend if I could remember its name.

Glad to hear you got it running. It might help others in a similar position if you would tell us some details of the Hall Effect sensor you bought. Part number, description, vendor, price etc.

A vacuum reservoir of the size shown would be hard to miss. If you don't see one perhaps it's because you don't have one. I didn't on mine.

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