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Robert
Robert, UK Qualified Car Technician
Category: Audi
Satisfied Customers: 4438
Experience:  Fully qualified 19+yrs exp/self employed technician in the UK
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I have an A4 2.0 diesel with 65000 miles on clock. Sounds very

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I have an A4 2.0 diesel with 65000 miles on clock. Sounds very loose on idle and noisy like a tractor. Seems the turbo comes in not all the time.
Any ideas Joe.
Submitted: 11 months ago.
Category: Audi
Expert:  Robert replied 11 months ago.
Hi there.. Difficult to say without hearing it..But id say the best course of action and from what you have said with regards ***** ***** turbo not boosting or kicking in..then that would be the area of concern or at least the area id say that would need to be listened too...If it from the Turbo housing then its likely the internal shaft which the compressor and turbine wheel is attached is loose due to excessive wear caused by lack of oil feed..Once the intake.intercooler tube to the compressor housing has been removed to expose the compressor vane within the turbo itself..obviously with the engine off..feel inside for any excessive movement..if it can be wobbled about then the turbo is bad..you should only feel a very minor to vitrually no movement what so ever...If the turbo is deemed to be bad after investigation..then you will require a replacement or reconditioned turbo, the oil feed and return line aswell as after which a full oil and filter replacement...but as above from what you have noted there the Tubo would be best place to start checks id say..I do hope this helps
Customer: replied 11 months ago.
Another person mentioned the timing belt. Might this need to be replaced after 65000 miles.
Customer: replied 11 months ago.
Also the car failed its MOT ( our NCT) first time on smoke emissions of 7.4. After a long run and Dipetane it passed the next time with 0.24 reading. Everything seems to be connected. How would my mechanic start his diagnosis of the problem.
Customer: replied 11 months ago.
What about the ignition coil packs as well.
Expert:  Robert replied 11 months ago.
Diesels dont have Ignition coils packs thats only petrols.. Timing belts normally 75000miles or 60months which ever comes round first..and requires the entire timing belt kit inc that with all the associated pulleys the belt runs on....There could many things to cause failure of smoke emissons..Filters / injectors / turbo or wastegate sticking / egr valve / lack of use causing excessive build up of carbon/soot deposits and not allowing the engine to naturally burn it off through long periods of driving... Ideally your mechanic at least should be listening and pinning down the area suspect of the noise and that should include what i mentioned before with reagrds to the turbo..you have said that its intermittent in boosting so that would be the likely place to checkaswell as fre movement of the wastegate..obviously other areas with regards ***** ***** side of the engine would need to be ruled out and anything run off these belts should be inspected...if there are any warning lights on the dash since this occurred then that too may give an insight once its scanned whether any faults codes are stored etc...
Robert, UK Qualified Car Technician
Category: Audi
Satisfied Customers: 4438
Experience: Fully qualified 19+yrs exp/self employed technician in the UK
Robert and other Audi Specialists are ready to help you
Customer: replied 11 months ago.
Robert,After a deep inspection of the engine by my mechanic we have decided to do a replacement of the timing belt, pulleys, tensioner, etc along with replacing the balance shaft / oil pump unit. The balance shaft on this model can give trouble. Decided to do this first, hoping that the turbo is not the problem.
When I did the retest, the smoke level had gone down from 7.8 to 0.240. I passed.
Have you had any experience of balance shaft problems on Audi A4 TDI.IN addition I have read about ARCHOIL 6400 D as an effective system for cleaning - do you have any views on this.Joe.
Expert:  Robert replied 11 months ago.
Hi.. Its fairly well known on earlier engines codes BLB being the most common...where as later ones effectively have updated lastest balancer shaft/ pump units .there two types earlier with chain drive which was always problamatic and one geared balancer shafts..normally the failure was hex drive as they call it at the balancer shaft to the oil pump..normally this would rear its head with alot of engine noise maybe similar to what you describe but doesnt equate the fact of the turbo issue you mention..but with balancer unit failure normally the oil pressure warning is key in confirming issues on that...but yep as long as the balancer unit is the updated one then it should basically sort that engine out for good..As far as the cleaner..cant comment as i havent actually used myself.but i know exactly the product you note there..Again as i always say try a higher premium diesel first if that doesnt seem to provide a solution after some time..then i dont see any harm in going down the route of cleaner..having said that have used Cataclean and seen improvements using that..particular with diesels for smoke testing..could be worth looking into that too..

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