Cam housing sprocket moved during TB R&R while at 45 deg
05-21-2018, 02:15 AM
#1
Three Wheelin'
Thread Starter
Cam housing sprocket moved during TB R&R while at 45 deg
I am in the middle of a refresh. The motor is out and the crank was set to 45 degrees as recommended and the timing belt cam pulleys marked. For some reason the left (drivers side in my case for U.S.) jumped slightly at some point when I was removing the water pump or oil pump (guessing due to the movement) but unsure why.
I have tried to move it back with my hand but seems like there is some resistance. Is this a common thing and what would be the proper way to move it back so when I replace the WP and TB I am back aligned?
For reference, if looking at the sprocket from the front of the engine (it's the one on the right) it had moved in a clockwise motion almost an inch or a little less. So, I would need to turn counter clockwise to get it back to the original marking which I made on both sprockets after setting to 45 degrees.
Thanks for any help, wanting to figure this out the right way but also not force if something else is happening I'm unaware of.
Bryan
I have tried to move it back with my hand but seems like there is some resistance. Is this a common thing and what would be the proper way to move it back so when I replace the WP and TB I am back aligned?
For reference, if looking at the sprocket from the front of the engine (it's the one on the right) it had moved in a clockwise motion almost an inch or a little less. So, I would need to turn counter clockwise to get it back to the original marking which I made on both sprockets after setting to 45 degrees.
Thanks for any help, wanting to figure this out the right way but also not force if something else is happening I'm unaware of.
Bryan
05-21-2018, 02:26 AM
#2
Rennlist Member
Bryan,
The sprocket can jump although I am a little surprised by the amount you state. Either way the sprocket can and does self rotate from a position of valve spring compression to one where there is less spring resistance.
To get the sprocket back to where you want it to be, with the timing belt off the sprocket, it can be rotated safely in either direction assuming you are still locked at 45 degrees before TDC. when you rotate the sprocket do so using a 30mm wrench over the large hex washer- do not use a smaller wrench on the cam sprocket bolt to turn the cam position.
No way are you going to be able to turn the sprocket by hand only- the spring resistance is way too much for that.
The sprocket can jump although I am a little surprised by the amount you state. Either way the sprocket can and does self rotate from a position of valve spring compression to one where there is less spring resistance.
To get the sprocket back to where you want it to be, with the timing belt off the sprocket, it can be rotated safely in either direction assuming you are still locked at 45 degrees before TDC. when you rotate the sprocket do so using a 30mm wrench over the large hex washer- do not use a smaller wrench on the cam sprocket bolt to turn the cam position.
No way are you going to be able to turn the sprocket by hand only- the spring resistance is way too much for that.
05-21-2018, 09:41 AM
#3
Nordschleife Master
Remain calm. All is well.
Since you are asking, I will take it that you aren't sure. This answer will cover everything, in case you don't know or in case someone else reads it.
Putting the crank at 45* moves all of the pistons partway down the bore. As long as the crank isn't moved, there is no way the valves can hit the pistons. You can rotate the cams 'until the cows come home' with no risk for damage.
The cams will almost always jump some. The lobes are pushing on the lifters and the springs will resist. It will find the 'point of least resistance', where ever that is, closest to where it was. An inch of gear circumference isn't all that much. You can rotate the cams around and feel this process, as long as the crank is still at 45*. The resistance you will feel on the cam gear will kind of 'bounce around', depending on how many valves are being pushed and how far down they are at any given point.
If you put the cam gear back to 'correct' right now, the chances are that it will jump again at some point. Probably immediately after you take your hand off of it. I would wait until you are stringing the belt. The easiest way is to put a wrench on the washer (not the bolt) on the front of the cam gear. Once more: Not the bolt that holds the cam gear, the washer has a 'nut shape' on it, used to counter hold when tightening or loosening the bolt for the cam gear. Use that. I could rotate my 16v cams by hand. It was not easy. I doubt you can turn 32v cam gears by hand. You don't say what you have.
I've heard arguments that you should only turn the cam clockwise (direction of engine rotation when running), but for that inch or so to put it 'right', I would simply turn it the shortest way.
Since you are asking, I will take it that you aren't sure. This answer will cover everything, in case you don't know or in case someone else reads it.
Putting the crank at 45* moves all of the pistons partway down the bore. As long as the crank isn't moved, there is no way the valves can hit the pistons. You can rotate the cams 'until the cows come home' with no risk for damage.
The cams will almost always jump some. The lobes are pushing on the lifters and the springs will resist. It will find the 'point of least resistance', where ever that is, closest to where it was. An inch of gear circumference isn't all that much. You can rotate the cams around and feel this process, as long as the crank is still at 45*. The resistance you will feel on the cam gear will kind of 'bounce around', depending on how many valves are being pushed and how far down they are at any given point.
If you put the cam gear back to 'correct' right now, the chances are that it will jump again at some point. Probably immediately after you take your hand off of it. I would wait until you are stringing the belt. The easiest way is to put a wrench on the washer (not the bolt) on the front of the cam gear. Once more: Not the bolt that holds the cam gear, the washer has a 'nut shape' on it, used to counter hold when tightening or loosening the bolt for the cam gear. Use that. I could rotate my 16v cams by hand. It was not easy. I doubt you can turn 32v cam gears by hand. You don't say what you have.
I've heard arguments that you should only turn the cam clockwise (direction of engine rotation when running), but for that inch or so to put it 'right', I would simply turn it the shortest way.
05-21-2018, 11:04 AM
#4
Three Wheelin'
Thread Starter
I got it!! Thank you both for the helpful info. It has been so long since the last time I forgot as to this potential. I new it jumped last time but only by a little.
Yes, all things are still in place so just a jump to the path of least resistance as mentioned. Thanks again for the help!
I do agree that waiting until I load the belt may make sense as it may just jump again..
Yes, all things are still in place so just a jump to the path of least resistance as mentioned. Thanks again for the help!
I do agree that waiting until I load the belt may make sense as it may just jump again..
05-21-2018, 01:48 PM
#5
Rennlist Member
Once the belt is in position take a careful look at the index marks on both sprockets to ensure they are not a tooth out. Even if they are it is not a big deal to rectify such. This is also a good time to check/adjust the cam timing if needs be with the 32VR tool which you should have if you are going to take on such jobs. Needless to say if the sprockets have not been off there is no need to do the cam timing assuming you are happy with it.