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Timing chain gear cam slip

2K views 17 replies 3 participants last post by  Hillingdoner 
#1 ·
Searched through and read somewhat conflicting info so thought I'd ask to be sure before I proceed.

Doing the timing chain, guide and cam gear change job. Following along and took the route that the cam followers did not need to be removed on the passenger side to do the job. Now perhaps paying the price.

Everything fine on the passenger side until I go to put the new cam gear back on and find the cam as slipped VERY slightly so that with the gear aligned on the chain to match the old gear, the cam does not align with the slot. Was just a fraction off so I thought perhaps I could turn the cam that tiny tiny bit back and get everything to line back up.

Cam spring tension slipped and the cam jumped forward to now what I have pictured below.

Where my questions come in is in the fix.

Seems one fix seems to say that you have to put the cam gear back on however it will align with the cam and not the chain. When all back together with the chain on (just out of alignment) you turn the engine at the crank and pull all the cam followers on the passenger side as rotation allows. Then get the engine to tdc again, pull the gear, spin the cam so that it is lined up with the marks again now it should be, put the cam gear on so it aligns with the previous chain mark and install it on the cam.

If this is the only route to fix, is it safe to put the gear on the cam and have the cam not aligned correctly (by the amount in the pic) to the chain and turn the engine? Wondering about valve/piston contact potential.

Another "fix" was alluded to on a post in which you grab the cam in the centre, where the two tab looking pieces are, with a pair of large pliers and simply turn the cam backwards to align everything again. Then put your new gear that is matched to the mark on the timing chain back on. Hope that description makes sense. Is this safe to do?

If so, I assume advisable to remove the oiler tube. I do have a large pair of slip joint pliers. Tips, concerns, issues?

Thanks for the help all.
 
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#2 ·
Yes you can grab the cam with large pliers and rotate it back to where it was and then put the cam gear on..
You need to make sure that you have the chain tensioner installed when rotating the engine from the crank bolt below.
If you do not have the tensioner installed when doing that , there is enough slack in the chain for the cam to slip..
Also note; when you are on TDC down below the left cam mark will trail just slightly, That is normal.. As far as valve contact, You can be 2 teeth off, which is 18 Degrees before you start hitting valves. Hope this helps..
 
#3 ·
So long story short, If the engine is on TDC down below.. With the tensioner out, move the cam back to position and then move the chain back over the cam taking up the slack. Put the chain tensioner back in before rotating and recheck your marks.. " passenger" side cam mark with trail just slightly..
Also that looks like the drivers side cam tower not the passengers correct?
 
#6 ·
I currently have tension on the chain with a bungee to the hood. Old cam gear just sitting in place as that is what I tried turn the cam back that tiny bit initially before it spring slipped to where it is now.

So, pull off the old gear, place the new gear in the chain aligned with the marks I made on chain and gear, turn the cam back with a pair of pliers so that the timing chain aligned gear now aligns with the key, install gear on cam.

When you say mark will trail I assume you mean that the mark on the gear side will be slightly to the left of the mark on the cam side or visa versa?

Picture is of the passenger side set up. Not started on the driver side yet.

Once I've got the passenger side fixed I need to do the driver side gear and guides. Then put the tensioner on and then I can do the chain swap.

Hope that all makes sense.

Thanks for your help.
 
#4 ·
Thanks! That is exactly what I needed to know.

Now if it would just get a little warmer than 20 something degrees in the garage..... Hopefully this afternoon. Get all aligned again using the plier method and get that gear on.

Thanks also on the tensioner info. The tensioner is currently off the car, but I am not and have not turned the engine from the initial tdc setting before starting the job. I still need to get the driver side gear and guides changed after I get the passenger side done. I believe that the manual says that is when you install the tensioner before you start rotating the engine for the chain swap (might be remember wrong as not looking at it). Sound correct?

I'll see how tough it is to get into the cam to turn it, but think I may need to remove the oiler tube to be safe. So, that means ordering another set of the plastic oilers for it (just replaced them a few days ago grr) as I read that once installed, if you remove them and try to reinstall they will not hold the same pressure or some such and may starve the cam for oil required. Sound right? I assume it is something to do with the supply side of the tube not sealing as tightly on reinstall and so does not get the oil through the tube like it would on a new install.
 
#5 ·
Yes , good Idea to have the tensioner in when doing the chain swap. Do you have the timing chain guide tool? if not, so the chain does not slip again on the cam while turning, You can use vise grips to hold the chain on the cam when turning.. You can do this in small increments. The proper way however is to use the guide tool that keeps the chain on the gear when turning the engine and usually using an additional person to feed it on.. One more tip that make the job go much more smoothly is to take out the spark plugs which eliminated the resistance for the engine compression when rotating.. Good Luck !
 
#9 ·
Hi,

Thanks for the tips.

I have the vise grips all set as I don't have the tool. I do have the plugs out already. Guess the lobe on the cam was just spring loaded and slippery enough that it slipped forward while trying to get all aligned again. If I end up doing this job again down the road, at least for me, I'll not skip the remove cam follower step I think. Hind sight.
 
#13 ·
Yes. Changed the curved long rail. Just ordered the insert rather than the whole piece. Also changed the short rail (so essentially both lol) on that side. While I'm thinking of it, the short rail, from the pin holes, has a longer side extending out and a shorter side. Did not remember which side went up when I went to reinstall. Did a little searching around and looks like the shorter of the two sides goes up (towards the cam gear). Sound right?

Thought I'd double check that while I'm still there as it were.

All MB parts by the way. Except for the gears. They are SWAG and the chain is JWIS (probably not spelling that)
 
#16 ·
Gear is on and all is aligned again. Well at least how it was before I pulled it apart. As you said, the passenger side marks did not line up perfectly to begin with. Now just have to do the driver side guides and gear once the guide I neglected to order the first go round arrives tomorrow. Then on to the chain and finally start putting things back together again.
 
#18 ·
Once I verified it was okay on here it ended up being super simple to fix.

Took the oiler tube off, simple. Put new gear in the chain and aligned the marks I'd made to keep everything in time with the old chain. Then, while gripping the prong/flats in the middle of the cam (look like they are purpose built for this very thing) with a large pair of slip joint pliers, I turned the cam back and aligned the key with the new cam sprocket. Everything slipped right together and all is aligned how it was when I first pulled everything apart to do that side. As I said, ended up being super simple and easy to do.

Hope that makes sense.

Now just waiting on the remaining guide, that I missed ordering enough of, to arrive today so I can get the job done. Always a pain waiting on parts.
 
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