Hi. Don't know if anyone reads this forum. I'm after some advice before I source a replacement engine. Car has suffered from lack of servicing, has done 100K miles, at least 30K miles with noisy tappets. Just replaced the tappets, initially seemed ok, now noticing a noise (sounds like big end knock). Seems quiet when cold but gets noisier when engine reaches normal temp. Sounds like a diesel when ticking over, not noticeable around 1500 to 2000 RPM, but can hear when changing gear (the slight blip in revs between gear change). Seems worse when the engine is over 2000RPM and not under load.

We did have an oil warning for some time, I found the breathers and oil separator were clogged, after cleaning this out and changing the oil and filter that problem seems to be gone, however occasionally on a cold start the MIL light flashes on (VAG-COM reports multiple cylinder misfire). This didn't happen before I changed the tappets.

The camshaft bearings I noticed are worn (scored). The lobes are fine. Having not done one of these before I'm not sure how the roller rockers should be, they all move but there is play in all of the rollers, is this normal? I removed the sump and cleaned the strainer in case this was also clogged; while at it i had a feel of the big-end bearings and could feel no play in them.

I'm going to get a stethoscope to try and locate the noise, could this be an oil pressure issue, perhaps from the worn camshaft bearings? Is it more likely to be big end failure?

I'm just wondering if the new tappets could be causing some issues, one of two were quite tight going into their bores. The old ones I took out were in poor condition.

I'm pretty much at the stage of trying to source a good used engine since a cylinder head is not cheap (required to sort out the scored cam bearings, along with a camshaft and cover), big end shells seem hard to source (and may fail rapidly if the crank is worn) I can't do the main bearings or have the crack reconditioned since VW state the main bearing caps can't be removed without distorting the block.

I welcome any suggestions on this one. I intend to remove the cam cover again and give the tappet bores a good clean out with some fine wet paper in case one or two are sticking, I'd like to get as much mileage as I can from this engine but obviously don't want a catastrophic failure while driving.

If I do get an engine I will report back on this one when I strip the current engine down after removal.

Advice for what it's worth, keep an eye on the breather pipes, they fill with condensation which mixed with the oil turns into mayo and blocks the system. Some of this crap then seems to find it's way back into the sump, where the strainer and oil filter cop for it, then you get the oil pressure warnings. At this stage I feel the damage has maybe already been done.

Will report back, but feel free to offer suggestions. In particular under what conditions would a big end knock be most noticeable? Under acceleration, or when the throttle is eased off (less load) Like I said I can't feel any play there, that's not to say they aren't worn (scored perhaps) to the point where they can't sustain a good oil wedge

I've done a lot of work on older engines in the past, the tolerances in these might be much smaller.

Thanks for listening, feel free to offer advice.