Cam sprocket wearing groove on back tbelt cover

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

OK, got one of the oil seals out, what a bear. Last mechanic used some RTV-like sealant to set them in and boy did it ever hold. [BTW ended up getting the Lisle 58430 seal puller. That got this first seal out in like 3 mins, after I had been working on it with various other tools for hours. Highly recommend it.] Still am struggling with that second one, though.

I was a bit surprised by what I found under that first oil seal. There was a snap ring/c-clip and the proper spacer, in the order which the FSM specifies. But ring was just sitting on the shaft, not snapped in??? At first there did not seem to be a groove for the snap ring. But in looking more closely there is a groove for the snap ring, but the spacer was sitting over it; if one uses the groove for the snap ring you can't fit the spacer behind it. Now it appears that this cam has about the right end play without the spacer with just the snap ring in place (just eyeballing it, have not mic'd it yet).

So I am wondering what is going on here. Did VM come out with a new designed cam which just uses only a snap ring and no spacer to hold the end play (would explain why all the parts places don't carry the spacer anymore)??? Anyone know if something like this happened? Seems like it might lead to excessive wear, having a hard steel snap ring rubbing directly against the aluminum intake/valve cover, but I guess it does get oil feed. Or is the FSM just wrong and the spacer goes outside the snap ring (although can't see what the purpose of that would be).

Anybody who has replaced their cams have any idea what changed from the FSM to the cam I have?

TIA

DieselJeepLuvr · **Posted:** Fri Mar 01, 2019 1:44 am

Steve,

The spacer IS necessary. The cam lobes are usually ground to provide a small amount of rearward force on the cams this keeps the spacer tight up against the intake. Without the spacer is wil essentially use the C clip as a drill bit not to mention cause your cam gears to rub against the rear housing (as you already know). If you can't get enough slack to install the clip with the spacer in place, try rotating the engine counter clockwise a couple of revolutions but you may have too much freeplay at the back of the intake to do you any good. Removing the intake may be your only recourse.

Mountainman · **Posted:** Fri Mar 01, 2019 11:31 am

I do recall something about the new cams being different, but I can't remember exactly. If you hunt threads with google you will likely find the discussion. It's been 2 or 3 years. I'll try to find it

Mountainman · **Posted:** Fri Mar 01, 2019 11:39 am

Found it.

viewtopic.php?f=5&t=77645

I believe he's right, as I had a little trouble with new style cams as well...

Long story short, toss the spacers, and if you have just a slight bit of end play that is about the same on both cams then you're good. Measure it if you can. 2 minutes at a machine shop if not and you're worried about it

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

Thanks All-

Got the new seals and replacement c-clips today (old clips were stretched for a couple of years not being in their groove, so thought it best to replace them). Put the c-clips in and thought I would spin each cam shaft around to check for binding and see how the valve train felt (not to worry, crank locked at TDC+90 so no chance of valve contact). Both shafts spin just fine. The intake has four even resistance spots one for each cyl. The exhaust however had one cyl spot which was there but seemed easier than the others (turning by hand).

Perhaps I am worrying over nothing, but my thought is that one weak cyl on the exhaust has a collapsed lifter or broken rocker arm (or the rocker just fell off its valve).

What do folks think? Am I making something out of nothing here? I would rather not pull the intake to check for nothing. Although it might be good to see what the cams and lifters all look like after this cam movement, I don't want to make more work for myself. And I can't really do it in the current spot I am working in, so it will have to wait. How bad would it be to reassemble and drive it a bit and pull the intake later, if there is a problem in there. Perhaps do the MAP quantity test to see if it points to a bad lifter/rocker. Thoughts?

DieselJeepLuvr · **Posted:** Tue Mar 05, 2019 11:04 pm

Doesn't sound right to me. Could be a bent valve. Half a$$ed is never a good thing. How far do you need to go to get it somewhere you can take your time working on it? You could try AAA or a buddy with a tow strap and a 12 pack...

geordi · **Posted:** Tue Mar 05, 2019 11:25 pm

There are 8 valves on each side, and the lobes are close together in dwell time but do not match perfectly. One valve per cylinder opens before the other, and the later open closes later. Thus there is a longer duration for opening and closing than if they matched and acted in perfect unison.

Does this feel like one of the dwell times (expressed as duration of resistance across a certain range of rotation of the cam) is perhaps shorter than the others? Not all the lifters will be compressed the same way, as they are ejecting their oil charge as you rotate the cam. Some lifters may "leak" easier than others, this means nothing when the engine is running. I doubt you caused a rocker to drop, but they CAN be collapsed from bearing wear, and that would feel like an "easier" rotation across that particular camshaft lobe.

WolverineFW · **Posted:** Tue Mar 05, 2019 11:40 pm

Time for a cylinder compression test..

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Mountainman · **Posted:** Tue Mar 05, 2019 11:48 pm

I would not run it without carefully inspecting all contact points in the top end, as any damage might lead to a dropped valve, not worth the chance.

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

Thanks Geordi.

It's a bit hard for me to measure dwell time/rotation (I was just turning the cam sprocket by hand), but I suppose I could go back and do it with a ratchet and note the angles. What I felt was high resistance as I was pushing the valves down (or I assume that is what was going on since I have no way to actually see that happen), and then after some point the cam would snap a bit more forward (again assuming that was the valves pushing the lobes around). This happens 4 times in a full rotation. For this one position on the exhaust, it took less hand force to push the valves down and it snaps forward but not as strongly as the other 3 cyls. I was thinking that it may be that only one of that cyl's valves is being compressed (or that both are but not as far) and that's why the forces are less on that one.

I like the idea that it may just be a lifter or two that has leaked down some on that cyl. I don't believe that I could have knocked a rocker off in my work here (I didn't move the cam any further than it was going on its own). And I don't think that any rockers had broken previously; at least I did not hear anything or feel any big loss of power which I assume would happen when a rocker breaks or isn't working. It's hard to remember sometimes, but originally I was looking for the source of a cam sensor error light, not for possible broken rockers or the like (hard to remember you were going to drain the swamp when you are up to your neck in alligators

).

If there was some way to decide if there is a rocker/lifter issue without pulling the intake, that would be great. Alternatively if I just reassemble and run it, if there are no obviously bad sounds how much risk of doing extensive damage is there? [I know, a bit hard to ask someone else to take a gamble, but I'd just like to get some idea of what is likely here]

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

Thanks Wolfverine & Mtnman, your posts came in as I was posting back to Geordi.

I guess I am not clear what a compression test would show here. If an exhaust valve wasn't opening, assuming all less is OK with the cyl, I would think compression would show as fine. Intake valve might be pretty obvious, but would a comp test care is some gas wasn't getting out? the engine performance would suffer sure, I just don't know that a comp test would pick it up.

Mountainman, you are right, the thorough way to go about this is to pull the intake and see what's there. And I think that is definitely in the future of this engine, just not right now. At best, I could seal up the cams, and leave the engine in its current partially assembled state until I get another place to do the intake removal (there isn't space to do more disassembly where it is now, and I need to vacate there asap). It would certainly be a lot easier to put it back to running, do the map test and listen for other problems (and move it to a new work location), but you have a point, there is a risk of big damage. I'd just like some way to predict that without looking under the intake.

Maybe I should ask, I've seen the vid's of CRDs with busted rockers and they makes quite a racket. No such noises from this engine prior to my work on the timing belt. What are the symptoms of a rocker that just fell off its valve stem? Does it make any noises or have any other obvious symptoms? If a rocker does fall off, how are the clearances under there, can it just lie safely or is it likely to get caught in something and break it?

Thoughts?

Mountainman · **Posted:** Wed Mar 06, 2019 10:40 am

I've seen an engine with one rocker knocked off and I couldn't hear it. It was snapped in half. I've also seen an engine where a collapsed rocker managed to cause a dropped valve when it got wedged just right, although that's a rare situation.

Steve777 · **Joined:** Fri Oct 16, 2015 11:31 pm **Posts:** 279

Well it's been longer than I thought, but I got my workspace back, and proceeded to remove the cam/intake on this CRD. What I found is the rear most exhaust rocker was knocked off its lifter and wedged in the depression for its valve. Everything else looked good. The roller on the lifter has some metal damage at one edge. And the cam has a relatively small scratch in the lobe near one edge. I have no idea if this damage was done when the PO had the lifters all replaced, but I suspect it happened before I got the car. I guess could have happened due to the camshaft motion when the circle clip was mis-installed, but who knows. I also suppose there might be some hidden damage (like the rocker bent the valve stem as it was falling over), but can't say about that until I get a good lifter/rocker back in there and try turning it, nothing looks out of place just eyeballing it.

Not sure yet if this scratch in the lobe can be removed well enough to use. It's about 1/2" long and fairly narrow; deep enough to feel with your finger nail, and located near one edge of the cam around the point of the lobe. Given that the rockers all have relatively wide roller bearing surfaces it seem like it should be good enough as long as there is no metal raised up after repairs, but I thought I would ask the experts here with more machining and engine experience. Also looking for a cam grinding place around Denver or the front range, but have not had a lot of luck finding one yet, if anyone has a recommendation.

So all in all, not too bad, one new lifter rocker, maybe a cam, Tbelt, intake gasket (or do people reuse those?), and should get this fixed up. Of coarse, I'll also replace the glow plugs and thermostat while I am in here. Still debating about putting in ARP studs. Anything else I should be doing while it is opened up?

TKB4 · **Posted:** Wed Jul 17, 2019 9:57 pm

I have reused the intake gasket twice and had no leaks Sir Sam is in the Denver area and may well be able to help you find a suitable shop. I would pm him if no other helpful responses. Glad you got to it and there were not any worse problems. I would highly recommend the ARP studs or if can't right now maybe consider replacing the current factory head bolts with a set of new factory head bolts one by one. Many have an extra set they received when buying a head gasket before it was readily available separately. I probably have some around here.

Cam sprocket wearing groove on back tbelt cover

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