What about the balance shaft bearings at the other end?

[NotMyGTI]

Been doing some more digging - I'm not so sure that the balance shafts have needle bearings after all, FWIW. Saw some info indicating that they may be actually plain-type bearings as well - with the aluminum housing ID directly being the outer plain bearing surface. Regarding that babbitt rear bearing down in the bore, wouldn't it be as vulnerable to scoring due to contaminants or oil starvation as any other well-oiled bearing in the engine (and don't those shafts spin at 2X engine RPM as well)? I've seen photos of scoring and embedded particles in these babbitt bearings, just like any other. Thanks for the part number. I had cautiously arrived at the same part number - but wasn't 100% certain of a direct connection to our balance shafts. Another puzzle piece. I'll call the dealer with the part number and see what they say. I need to go back to the factory shop manual again and look for this bearing with a "magnifying glass". Surely....it must be in there somewhere.

Regarding the access to the bearing on he water pump side - is the bore actually closed off by the block (except for water pump drive stub) or is the bore constant all the way out, being closed off only by the water pump stub _oil seal_? I thought that it would be the latter.

 

[NotMyGTI]

I've seen a lot of comments about oil pressure issues on these engines in my searches - including some where the balance shafts were replaced, hoping to "fix" a low oil pressure problem. In many cases, it did not "fix" the problem. How likely is it that a potential source for low oil pressure are one or both of those babbitt bearings at the bottom of the bore - the ones that no one (or few) seems to look at, perhaps because it's difficult to view them without a borescope and difficult to change out (at least without special tools) while the engine is in the car. Changing the balance shaft only "fixes" one side of a damaged plain bearing pair (and the more durable side at that). The side that stayed behind is the softer babbitt bearing. Just thinking out loud. I don't think that I have ever seen an engine part so shrouded in mystery.

 

[NotMyGTI]

I've been studying the question of pulling out those problem little filter screens in the balance shafts. I've seen a lot of photos of filter screens holding on to a lot of junk, eventually blocking the bearing oil passages. I realized that, without those oil screens, _every bit_ of that very junk would have found its way into the bearing - certainly resulting in increased bearing wear with the increased possibility of balance shaft demise long ago. Of course, the amount of wear depends on the amount (and type) of junk deposits. It seems to me that VW engineering has provided an excess number of oil pathways into the bearing, possibly to compensate for their eventual restriction/blockage. I suspect that, in a perfect world, one passage may possibly be enough to provide adequate lubrication per bearing. This seems to be the standard in most, if not all, applications that I have ever seen. VW provided what - three or four oil entry points? So - those screens have a really fine mesh and do a good job of catching junk - but they _will_ eventually get full as they have no way to _ever_ clean themselves out. Period. Just like your engine oil filter - does a great job at catching the junk but it, too, is of a finite size will eventually fill up and block the oil if you do not change it soon enough (thank goodness for the oil filter bypass!). Since you cannot change out the balance shaft screens under normal circumstances - it is up to the owner to be absolutely fastidious about regular (even early) oil/filter changes with the right specifications. Of course - that doesn't help those of us who acquired these cars second and third hand. Even under perfect conditions - I suppose that those filters could still eventually become blocked. How long will that take? It depends pretty wildly on how the engine was maintained over its lifetime.

So - with all that said, I will not be pulling out the screens if/when I change out these shafts.