VW / Audi TDI increased tappet noise since recent service

Maybe its because its now got 254K miles, or perhaps I've not had the radio on as loud, but my TDI has gotten more noticeablity tappy recently and its power seems a bit lacklustre.

It isn't consuming oil,water or smokey. It isn't running hot. I can't say I've noticed a huge drop in fuel economy. I never rev the bollox off it. It occasionally might touch 90mph (3000rpm) but usually does 70ish It just feels like its perhaps lost 20BHP and gained 10dBA somewhere along the line. It doesn't run unstable & idles quite easily @ 900rpm Are there any plausable reasons which could explain a power drop , other than just old age.

  1. As part of the service, I changed the air & fuel filters. It was a pain to bleed the air out of the fuel line but it did finally start. I've noticed there still is air bubbles in the fuel pipes. Could this be effecting the pump & combustion swirl ?
  2. My 1.9TD synergie feels more sprightly even though it only got 2 more BHP it weighs ½ton more. I can feel & hear the turbo quick in on my Pug/Cit diesel. I don't notice such an effect on my Audi 80. Could I have a leak or a blockage somewhere from my turbo/intercooler which might loose power & induce more noise ?

  1. Would a diagnostic check at a diesel tuning specialist be worthwhile. How do you compression test a TDI ?

Its got me to thinking its time to get rid of it, but I do have a conscience and even though its about to just get a fresh MOT, I don't want to knowingly sell someone a car that might have a terminal engine problem.

Reply to
Ebodski
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If it had a new cambelt on the service then perhaps the pump or cam timing is now incorrect. An experienced diesel tuning place can check the timing very quickly.

MrCheerful

Reply to
MrCheerful

Nope, the cambelt was changed 20K miles ago in summer 2002 . No probs since then at least

Reply to
Ebodski

if it has a turbo then maybe the turbo pipe is split or fallen off.

MrCheerful

Reply to
MrCheerful

Hmmm.. I've never really checked what pipes go where on this car ( Audi 80

93 ). I think its intercooler is buried somewhere under the inner wing.

Could this still create a higher tappet noise though ?

Reply to
Ebodski

it will be noisier generally but not really tappetty

Reply to
MrCheerful

Tappet noise can be reduced by doing a engine flush (add flushing oil to hot engine) followed by oil change with good quality semi-synthetic or fully synthetic oil.

Low power would be your MAF MAF (Mass Airflow Sensor)

This part fails frequently on many modern VWs, and the TDI is no exception. Answers to some common questions about the MAF on our TDIs:

a.. What does it do? The MAF measures the quantity of air flowing through the engine's intake, and passes that signal to the engine computer so it can adjust the fuel quantity accordingly. For a more detailed explanation, consult the Bentley manual or the technical forums at

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b.. Why does it fail? No one seems to know for a fact. MAFs are extremely delicate pieces of electronic equipment, and failure could be caused by heat, dust, manufacturing defect, and on and on. Bosch MAFs are failing in other brands as well, not just VW, and the problem is worldwide.

c.. What are symptoms of a failed MAF? The most obvious is a lack of power. In a total failure mode, you will find the engine makes almost no boost, you no longer hear the turbo spool up (whistle) when you get on the throttle. You will likely have a hard time climbing hills. In a gradual failure, power will slowly decrease, perhaps without you noticing, especially if you are a moderate driver. If you have a boost gauge, the loss of boost is easy to see. I've personally found that a bad MAF can also cause a rich or unburned fuel smell at idle.

d.. How do I know for a fact that it's failed/failing? If you suspect a bad MAF, the best way to tell if your MAF is dead is to replace it with a new one and see if you can feel the difference. Most people don't have the luxury of being able to keep a new spare on hand, so you can use a VAG scanner like the Ross-Tech VAGCOM to check the MAF while you are driving. Go into measuring block 3, and look at the values for "measured airflow" and "specified airflow". With a good MAF, I always find that the measured airflow is well over the specified values, often in the

800mg range, but sometimes as much as 1000mg. A bad MAF will show specified and actual values in the 400-500 range, very close to each other and not varying much at all.
Reply to
Yoda

It is serviced every 10K with fully synthetic XFE millers oil. It had and oil/air/fuel filter change on 4th Oct.

I think your suggestion will just be throwing £40 down the drain.

The MAF just failed on my dads GM Vauxhall Vectra 2.0DTI. Its only got 45K mikes & only just years old.

The symptoms about power loss are there, but I wouldn't say its got a dramatic loss, just seems a little flat thats all. In the 2½ yrs I've had it, I've never really heard a turbo whistle like I get with my Citroen

1.9TD.

If the MAF is failing, is it mechanical failure or electrical ? i.e does the vane stick, or is like the vane activates a potentiometer and thats not giving a correct signal to the ECU ? If the MAF fails mechanically, can't they be clean out / polished / lubricated Can a failing MAF induce higher tappet noise ?

You've obviously posted a piece of copied text, but most of this NG including me wouldn't have a clue what you are on about with " go the measuring block 3". I pressume you are referring to some gadget. Can you detail the gadget and how much it costs.

Finally, does 254K miles qualify me for any special awards @

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like a free TDI coffee mug? lol

Reply to
Ebodski

Its a hot film type MAF on these, and whilst there is no moving parts, what basically happens is it fails to signal to the ecu the increaased airflow which would demand more fuel to get the power, so hence it feels flat. They dropoff over a period, so you are unlikely to notice a sudden change, unless you drive another car. As you did though, I would check all the turbo hoses and inlet trunking for splits and loose connections that could allow a loss of boost first. And you should definately not have air bubbles in the fuel lines, sort this out too before condeming the MAF. That said, they do regually fail at 60-100k mile intervals...

Tim..

Tim..

Reply to
Tim..

The gadget referred to in the OP's text is the "Ross-Tech VAGCOM"

There are more details on it on:

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and

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Ian

Reply to
Ian Riches

"It is serviced every 10K with fully synthetic XFE millers oil. It had and oil/air/fuel filter change on 4th Oct.

I think your suggestion will just be throwing £40 down the drain."

I agree with on this but at 254K miles a new set of hydraulic tappets might be the answer. With regards to the MAF a simple without Vag-com equipment is to unplug it...If this makes no difference that a new maf is needed

Reply to
Yoda

I've just been on the driveway earlier and unplugged the MAF connector. I thought your suggestion was a bit bizarre, because I thought the car wouldn't start without it. ( i.e just display a red ECU light on my dash ) ....strangely enough it started & revved etc . I didn't take it on the road because I've got 3 kids to look after tonight.

But does the above fact mean that my MAF is defunct. I must admit it does look a bit scrabby and I think it is the original.

Back to the tappets. I know these are hydraulic devices instead of shims, but are they easy to replace ? I don't have a maintenance manual for the A80 TDI ( no Haynes one in existance ). Does the cam have to be stripped out ? Any links available to shoe pics of the overhaul process ( preferablably A80 / A100 or B5 Passat , ie. longitudinal engines )

Also, the comment I made about air in my fuel line. Should I be bleeding this out by the filter top screw or water drain ?

Reply to
Ebodski

Yes I think so I had 2 Maf sensors fail on me... on my Audi A4 TDI 110bhp

2000. The best replacement strangely is to fit a Mercedes maf which cheaper a gives no problems I can get the Part Number if you need it

Yes the cam has to stripped out Haynes do a manaul for the A4 which could help you

The top screw is to allow water to be drained from the filter ....your system is self bleeding but if there is a blockage in the system the fuel injection pump will suck air into the fuel line

Reply to
Yoda

My MAF is Bosch 0 281 002 072. Is there anyway to verify if the same MAF is common to more mainstream cars like Fords / GMs so I can try to get a scrapyard one

Reply to
Ebodski

Try this link for parts

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No needs to from a VAG car seat, skoda, VW or Audi. one from a 2.0L petrol model will also work Check out the link for more info

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Reply to
Yoda

I am aware of GSF and found that a new unit is £110+vat

Thats okay to pay providing the old unit is definately busted.

I tried driving today withthe MAF unplugged, but it did make a difference. I wasn't just weedy on power, it feel like the turbo had fell of.

Does the MAF fail like a lightbulb i.e on/off, or can it just give a bad signal and loose 'say' 20% signal ?

I took off the MAF and checked it. the metal vane moves freely, but I when I tried to continuity check the connecter terminals, I couldn't spot a resistance anywhere..

I aslo noticed my intercooler > inlet manifold pipe was loose because its retaining bracket to the underside of the turbo had sheared. Is that a common failure ?

Reply to
Ebodski

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