V6 TDI: Camshaft Problems & Solutions

Hi.
I'm helping a friend install new camshafts in a 2.5 TDI (2002, Audi A4, AYM, 155 hp). The cylinder heads have been removed, and we wanted to test the new camshafts for smooth operation. Each camshaft can be easily rotated individually in its guides with our fingers when no other camshaft is present. However, when both new camshafts are placed in the heads, they jam at one point, while the other doesn't jam at all or only slightly. Between those points, the resistance gradually increases or decreases.

Has anyone ever observed this before? The waves are likely due to imperfections in the accessories, specifically poorly pressed gears or slightly bent shafts.

We can rule out other errors; we tested the camshafts without the lifters and pressure plates, all the covers are properly installed, and everything turns smoothly with the old camshafts (even though they are worn on the lobes).

My only guess is that the waves need to be phased in, but I can hardly imagine them being deliberately pre-set like that. Does anyone know anything about this, or do we simply need to get different waves?

Best regards, Matze.

P.S.: We are currently in the workshop and just twiddling our thumbs, and we would appreciate a prompt response :

I tried swapping some components around to see if the problem was related to a specific part. Whatever it is, it's definitely not normal. And how stuck are we talking about here?

Best regards, Marcus.

hi.

"Yes, I've already tried it on one head. It was much easier with an old one (the long one with the belt-driven mechanism) and a new one, but it's still not quite right. If I use the short one from the old set and the long one with the belt-driven mechanism from the new set, it jams much more. If I use both new ones, it jams terribly. If I use both old ones, it doesn't jam at all."

"I can turn the old shafts with my finger at the gears, even when all the attachments are mounted. I can't turn the new ones at the fixed position without someone holding the head, and even at the loose position, they are still much harder to turn than the old shafts. Not to mention trying to turn them at the gears – you have to have the pulley wheel on, and you have to turn it with both hands..."

Greetings.

No way, that's not allowed! That's way too heavy. The gear side will get incredibly hot very quickly in operation! And then the oil film might break down, and the bearings will start to seize up in no time. Then the damage will be even greater afterwards.

I guess either the angle of the teeth is incorrect, or the gears warped during the hardening process and are no longer perfectly round.

You should definitely file a complaint about this, and since this issue isn't present with the other two new camshafts, you have something to argue with.


Best regards, Marcus.

Are the bevel gears from the Northwest (NW) of the same design?
When switching from a sliding bearing to a roller bearing lever, the face gears were spread apart.
So, essentially, there's a second row of teeth hidden behind a slot, and it's slightly offset to minimize running noise.
Is it possible that this process could also be applied to refurbished older camshafts?