[Vwdiesel] 91 Eco EXTRA noisy til warm - hydraulic lifters?

[Will Taygan]

The '91 eco is sick.  Extra noisy until engine is hot.  

Ran some diesel-purge through it.  Cracked the injector lines.  #3 and
#4 seems great - hard running when cracked, #1 and #2 made a tiny little
difference in how things were running. Hmmmm...

No big gasket symptoms, but extremely rattly when cold.  Power seems
adequate.  

I'm thinking there might be a hydraulic lifter not working when the oil
is cold (Rotella Synthetic 5w40 for the past 3 years).

I suppose the timing could have jumped, but is it likely to advance
itself??

This is my only VW diesel with a hydraulic head, the others are all
mechanical.

Re: lifters, what should I check for, and how hard is it to fix?

Thanks,

Will in Alaska.