Cam not able to rotate after installing new valve stem seals?

[gene jude]

I was installing new valve stem seals as my 2000 golf tdi with alh engine was smoking and consuming oil during startups and after prolonged periods of sitting at a stop light. I did the service without taking the head out of the car and used a homemade valve compressor tool to take out the valve keepers for the valve springs. After installing the new valve stem seals, reinstalling the cam lifters, reinstalling the cam, and finally retiming the engine, the engine wouldn't rotate more than like 15 or so degrees before or after TDC. I tried retiming it few more times and still the same result. Eventually, I verified that the timing mark was correct on the flywheel with a dial indicator in the bore and the mark was correct. Then I started to work back from there, first with the crank. I pulled the cam out so the valves wouldn't move to make sure the crank rotates to rule out if I dropped a valve or something. It rotated perfectly fine. Next, the cam. I reinstalled the cam and rotated the crank to 90 degrees before TDC with all the timing stuff off so that the valves couldn't hit the pistons and tried to rotate the cam. It wouldn't rotate more than a few degrees. This is my issue. I tried testing which valve was the problem by taking the cam out and pulling every lifter except for 2 on a cylinder and rotating the cam until it wouldn't rotate anymore (The cam does rotate freely without any of the lifter in). All of the lifters weren't able to be compressed all of the way at about the point in the cam lobe. I thought it maybe bent valves because of my tool as described in this thread, just maybe so extreme that it's causing the valve to not rotate when turning it by hand. So I pulled the cam, lifter, and valve spring out of one of the cylinders to see if I could, with my fingers and not push down to hard on the valve, move the valve. It was able to move all the down so that the notches for the keepers were almost able to hit the new valve stem seals with no issues.

I'm at a loss at the moment as I have no clue what to try next to test. I have pictures of inside the bore where the valve isn't able to move anymore as well as how the valve stem seal sits atop the valve guide.

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• gene jude
• Oct 9, 2025

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• gene jude
• Oct 9, 2025

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• gene jude
• Oct 9, 2025

Thoughts of what I should try next?

 

[oilhammer]

What part number prefix is on the new seals?

 

[gene jude]

These are the valve stem seals I bought. Would there be any numbering or lettering on the seal to look for?

 

[oilhammer]

No VAG part numbers in there. I'd just want to make sure they are the correct ones, that the little metal collar isn't too tall or something. Did they look the same as the ones you took out?

I've never messed with doing this on a TDI myself, because usually the valve guides are where the actual wear is.

 

[454k30]

Those should be the correct seals. In the photo, it doesn't look like the seal is seated all the way down on the guide. I did this job last year and had to drive them down gently with a socket so that they fully seated. They do encounter some resistance and then kind of pop down into place. They are a snug fit on those guides so perhaps you just need to knock them down a bit more.

 

[gene jude]

No VAG part numbers in there. I'd just want to make sure they are the correct ones, that the little metal collar isn't too tall or something. Did they look the same as the ones you took out?

I've never messed with doing this on a TDI myself, because usually the valve guides are where the actual wear is.

The new ones and the old ones did look the same. Wish I took a picture of the old ones as I did get rid of them a while ago. When I bought them the set came with extras so I'll have to see tomorrow if I can find them and see if they have any writing on them.

 

[gene jude]

Those should be the correct seals. In the photo, it doesn't look like the seal is seated all the way down on the guide. I did this job last year and had to drive them down gently with a socket so that they fully seated. They do encounter some resistance and then kind of pop down into place. They are a snug fit on those guides so perhaps you just need to knock them down a bit more.

I'll have to try that because when I pressed the new ones on, I didn't get that pop you described.

 

[454k30]

I'll have to try that because when I pressed the new ones on, I didn't get that pop you described.

Give it a shot anyway. I used a 10mm socket (maybe 11) and a lightweight hammer to drive them into place. Not smack the hell out of them, just enough to get them to seat.

 

[gene jude]

Sorry it's been a little bit since I was able to work on the car. What I tried instead was that I took two of the valve seals out and reinstalled the lifters on those two valves and had the other cam lifters out of the head with the crank at 90 degrees BTDC. I did this just to see if the seal was even the issue. After trying it, I wasn't able to rotate the cam a full rotation. Maybe it is bent valves after all? Should I just pull the head off to see?