Damaged Valve Seats? Causes & Repair.

After experiencing what was essentially a timing belt failure with my AFN at 121,000 km, and now after taking the engine to the repair shop for the second time, I'm suddenly hearing very strange noises!

At an engine speed of approximately 3500-4000 RPM during acceleration, I hear a very loud knocking sound. I don't hear anything in the lower RPM ranges.
While some people might say I'm imagining things, the sound was different before the engine damage. The knocking is so loud that I can hear it even at 200 km/h on the highway when I take my foot off the gas.

Now, my question to the elite.

Could it be, though I hope not, that the head has been torn off around the valve seat, causing the valve to shift out of its proper position? That would be the only explanation for me, since ALL the exhaust valves, valve guides, and valve stems have been replaced.

Hi,
Were the hydraulic lifters tested/replaced during the cylinder head overhaul?
It has reportedly happened that a valve resting on the piston can, in a way, "kill" the hydraulic lifter.

Regards,

Olli.

Yes, all the elements have been swapped.

g1om wrote:

Could it be, although I hope not, that the head has been cracked around the valve seat, causing the valve to shift out of its proper position?

That would be the only explanation for me, since ALL the exhaust valves and valve guides, as well as the valve stems, have been replaced.

Hi,

Were the valve seats on the cylinder head re-ground? If not, it's conceivable that knocking noises could be occurring in that area (-> new valves).

The valve seats have been recut, and the valve guides have also been replaced.
Is it possible for a crack to appear even after the seats have been repaired? How can I detect hairline cracks in the head?

g1om wrote:

How can I detect hairline cracks in the head?

Hi,

"In my opinion, how could a crack in the cylinder head cause knocking noises? I think a shifting valve guide during operation is unlikely."

'Hmm, with my BMW M20, I had the problem that the crankshaft bearings were completely worn out. I didn't notice anything unusual with the compression or oil consumption, but it was making a lot of noise, like a sewing machine. After replacing the cylinder head, the noise went away.'

Hello!

And the timing belt pulley? Is it secure? Is the camshaft new? If not, perhaps a cam lobe is damaged?

"On my old 1.6 diesel engine, there were shims between the hydraulic lifters and the camshaft lobes, which were available in various thicknesses. Is this also the case with modern TDI engines? If so, could there be excessive play due to a shim being too thick?"

"How are the new heads constructed, and where are the adjustment options located? Are they equipped with cam followers, or are they standard or non-adjustable? I haven't looked into this in a long time, so please forgive my barrage of questions. I couldn't find much information about it on the forum."

Greetings, Peter.

Hello,

The AFN has hydraulic lifters. Problems can only occur if too much adjustment has been made. In that case, the hydraulic element can no longer function properly.

Hello Michal II!

Do these shim plates also exist in modern hydraulic lifters?

What can go wrong during the installation and removal of a hydraulic strut?

Thank you for the information, Peter.

Hello,

The insert pads are only available for non-hydrostatic jacks.

Your old Golf probably had the common valve lifters of the time, which required regular checks and adjustment of the valve clearance using shims.