Sorry I've been AWOL... busy as I've ever been and ready for calm.
Ok, So sorry to make everybody wait.
The history of this mod-
I worked under a guy who has been turning wrenches on VW's for over 30 years (dealer and independently) and he has always pumped doctrine into my head and I don't really question it, cause he has tons of experience on VW Audi only VERY rarely wrong, and that's usually good enough for me.
This is also one of those cases, I know it's an upgrade firstly because he told me so, secondly because AFAIK every gas 4 cyl motor past 83 had it fitted. Most diesels past 83 AFAIK also have it.
This change persists all the way through the 1.8 8v gas cars, the na diesel 1.6, turbo diesel 1.6, ecodiesel, 1.9td's, ALH TDI's, 1.8t's and into the TDI-PD BEW code. In other words, they aren't doing it by chance.
So, obviously I'd like to know why he told me this so I called him up. (He's old school and doesn't really do the computer thing so I'm as close as it gets to his word). In other words, I wanted to make sure my story is right.
He says,
The story goes back to the old 1600 beetle motor. Apparently on hard cornering, the beetle would momentarily lose oil pressure even though it wasn't low on oil. (I have no I have no idea about the 1600 BTW) so they decided to use grooves in the crank itself.. This apparently helps to purge air bubbles from the oil more quickly and would preserve oil pressure. Not sure what year this happened, a blank that needs filled in obviously.
In the early diesel and gas cars (pre-83) they had a lot of the same issues, in fact they apparently were wiping out mains and #3 rod especially and putting holes in the blocks with oil still in the motor, and the mechanics at the dealers could pretty much tell how the motor died by looking at the mains. If #1 rod was trashed, then they just straight ran it out of oil (#1 rod is furthest from the pump) the low oil thing was common because they had valve seal issues then too, and the motors consumed ALOT of oil. But if #3 rod was trashed then they knew it had to be an aeration related failure. In conjunction they'd see the cam bearings all scratched to hell occasionally. Apparently this became a big deal and they were having to warranty motors right and left.
So they started adding the #4 main 360 slot.
The theory is that because #4 main lubes #3 rod, and #4 main oiling hole comes off the main galley right under where the head ooiling hole takes off from the main galley, that it would be the most affected by a pressure drop because of air or any "other reason I suppose"(it has to compete with the head for oil supply). I think this is even more true as hydraulic motors came in, because if they starved for oil at the head, you get to collapse lifter. I also think this is one of the reasons they went to the 36mm gear oil pump.
EDIT: also for those who dont have 2 holes in the #4 journal, the slot allows lubrication to #3 rod 100% of the time rather than only 50%.
So,
I'm bugging him for dealer documentation to the techs for the 83 model year that he says explains the changes in models and why they did it, this I think will put the issue (it's roots at least) to rest.
The pure fact that every car since 83 had this upgrade (with a few possible exceptions) show that it's a factory correction. It's done for a reason. To not do it, seems to undo a correction they intended.
I'm not so sure on the theory about loading the bearing too much with a slot in the bottom, these cranks are wicked stiff. Add the fact that TDI PD's are rocking 180 lb out of the gate (way more in Europe) and they have the same bearing..
Anyway, I hope to post a copy of the documentation soon.
Hope I've helped...
