Engine noise - Top end knocking/tapping, gases coming from oil filler.

[T5 Byron]

T5.1 2.0 TDI 100k CAAB

We only use the van for trips, and I've noticed a tapping noise that's got gradually worse over the last few months.

On checking under the he bonnet to try and locate the sound I opened the oil cap, and it was immediately clearer/louder.

There also what looks like exhaust gases, pumping out in time with the noise.

Other than the noise, there's no other indicator that something is wrong.

No warning lights or fault codes on VCDS.
Drivers well, no loss of power.

Just done two engine flushes, it's running fresh oil, and is regularly serviced.

So far, the shortlist of potential problems is:

- Damaged Camshaft, followers, lobes
- Sticky Lifters
- EGR valve stuck open

Appreciate any help narrowing down the cause. Will probably get it booked into VW for a diagnosis next week. Thanks

 

[DXX]

Some blow-by is normal, however that does look excessive.
You don’t mention the oil consumption rate?
You can get an idea of engine wear by completing an oil analysis, make sure the data entered is 100% correct. You’ll need a small syringe and some flexible tubing to fit down the dipstick tube to draw off the oil, easier done when warm.

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[T5 Byron]

@DXX Thanks for the fast reply!

Oil consumption rate – I've got no analysis/calculations if that's what you mean (can you find this in VCDS?) but since owning it, and putting 4k miles on it, the oil hasn't needed topping up.

It's had two oil changes during those 4k miles, one of which was this weekend in an attempt to tackle the noise.

The Vision oil test looks worthwhile, especially on a high-mileage vehicle. I'm guessing I need to put a few more miles on this fresh oil before extracting some for the test. I've got the old oil which contains some Liqui Moly engine flush – I guess that would skew the results.

Van is booked in with the nearest VW commercial garage this Friday, so hopefully, they'll be able to narrow things down.

 

[DXX]

can you find this in VCDS?)

No

I'm guessing I need to put a few more miles on this fresh oil before extracting some for the test.

Yes

I've got the old oil which contains some Liqui Moly engine flush – I guess that would skew the results.

Probably, also the oil sample needs to be uncontaminated as the analysis is looking at very small particles and quantities (PPM), oil drained into a bowl etc won’t be uncontaminated, hence the syringe and tube.