Cammy sounding 300tdi

My 300 has developed a cammy sounding knock/tap. It ticks over fine but starts to knock at around 2-2500rpm
Performance is unaffected at present but something is going to give if i don't locate the problem.
It does it whether warm or cold but seems marginally worse as it warms up.
I'm lead to believe cams rarely wear so was wondering if it was followers/guides and if so how to check and replace
Any other suggestions gratefully received

id look at the vac pump first

Sorry, forgot to mention, already checked that. It's nothing ancillary related, something internal with engine. Checked pump and cam timing several times, definitely something inside.

As James said + tappets

Mucky injector ?

craigmidlands said:

Sorry, forgot to mention, already checked that. It's nothing ancillary related, something internal with engine. Checked pump and cam timing several times, definitely something inside.

Click to expand...

how did you check it, youd need to remove head to check cam followers if a cam bearing had gone youd lose oil pressure

jamesmartin said:

how did you check it, youd need to remove head to check cam followers if a cam bearing had gone youd lose oil pressure

Click to expand...

Checked vac pump and all ancillaries so nothing left outside of engine. Put screwdriver on each injector and no knocking coming off any of those either????

Change injector washers, cheap and it cured my 200 that was doing similar.
Mine was worse under load/ acceleration.

I've heard dodgy injector washers, this is definitely a knock rather than a blow by of the washers. Guessing its a head off job to see whats going on in there.

craigmidlands said:

I've heard dodgy injector washers, this is definitely a knock rather than a blow by of the washers. Guessing its a head off job to see whats going on in there.

Click to expand...

I have heard that they can clack away for a long time, matter of fact my last Tdi 300, a 1997 clacked away from the time I bought it,all the time I had it, about 2 years, now a mate has it and has put another 100 thousand klm plus on it, it is still running great, still clattering away. I checked all the usual suspects to try and find the source of the noise, head off for new gasket, vac pump, cam, followers, tappet adjustment, timing etc, still noisy, give up, beats me.