Cam Sprocket Removal - potentially messed up timing

[JHZR2]

I believe I have noisy lifters on my 1991 Mercedes 300D 2.5 turbo.

I need to remove the cam.

I followed the FSM setting the engine to TDC. I used the cam marks, as the balancer is then showing chain wear. FSM says it’s designed to wear 2 degrees in the first 20k km.

I started to loosen the cam bolt. When I looked at the harmonic damper marks, they were way off, like almost 10 degrees. I held the sprocket in space by wedging it in place.

I’m concerned to turn the engine backwards. I have the chain tie wrapped to the gear so it can’t jump teeth.

This is how the FSM says to do it:

I didn’t that way with the shaft through the gear.

And the bolt removed:

I’m concerned about screwing up timing. I know I can always verify by looking at injection timing and turning the engine, but I don’t want to screw anything up.

Do I just turn the engine forwards/backwards the few degrees to get it back to where it was? Or what?

Thanks!

 

[KrisZ]

To clarify, the balancer was about 2 deg out before you unscrewed the timing sprocket and once you did it moved to about 10 deg out?

If so, since the FSM doesn’t specifically say to lock the crank shaft in place most likely residual pressure in a cylinder moved the crank. I would say you’re safe to rotate it backwards to 0 deg.

 

[JHZR2]

To clarify, the balancer was about 2 deg out before you unscrewed the timing sprocket and once you did it moved to about 10 deg out?

If so, since the FSM doesn’t specifically say to lock the crank shaft in place most likely residual pressure in a cylinder moved the crank. I would say you’re safe to rotate it backwards to 0 deg.

The way you check for timing chain wear is to align the cam TDC mark to a cam tower. Then the harmonic damper has the wear mark. Yes it was about 2 degrees off. FSM says the chains are designed to wear about 2 degrees in 20k km when new. So the chain and timing is where it needs to be.

Thus it was 2 degrees out but this was expected/normal.

Yes it went to 10 degrees, IIrC. So I’d need to moved backwards.

The cam has a little key on it. Thus it can really be only in one place. So I think then reinstalling at all marks lined up is correct.

I just don’t want to break anything. I certainly didn’t turn anything more than a few degrees.

 

[JHZR2]

Strangely, none checked out bad…

 

[KrisZ]

It’s a little strange that it went forward, did the cam sprocket mark still line up or did it go forward too?
If they went together that moving it back should be no problem. However if only the balancer side went forward, that means there was slack in the chain on that side, but there should be no slack there.

 

[JHZR2]

So the one thing I didn’t do was remove the chain tensioner. I have to wonder if that forced things to move.

 

[Trav]

Did you run MoS2 in that engine? How are the cam bearing shells?

 

[JHZR2]

Did you run MoS2 in that engine? How are the cam bearing shells?

No never ran MoS2.

They all had a great oil film and looked pretty consistent. This one has a scratch I guess. But that’s the worst I saw.

Unfortunately I still have the same noise. So a day and ten lifters wasted. Here it is at first startup. Valve lifters immediately pumped up, easy to hear, but the growling like tapping remained. Unlike any of my other 601/602/603 engines.

 

[mattd]

Honestly that sounds more like injector/combustion noise to me.

 

[Chris142]

How are the injectors? Sounds like an injector overfueling and causing a detonation knock. You can put a stethoscope on each line to hear the difference

 

[JHZR2]

Honestly that sounds more like injector/combustion noise to me.

Agree but I had the injectors refurbished and pop/balanced a few thousand miles ago.

How are the injectors? Sounds like an injector overfueling and causing a detonation knock. You can put a stethoscope on each line to hear the difference

When I bought the car the person selling it said it was lifters. These engines are known for occasional collapsed lifters.

As soon as I got the car I diagnosed and thought it was maybe injection. But the car runs beautifully, and I got the injectors popped/balanced.

That injector #1 is seemingly more “Metallic” sounding when I put a stethoscope on it. But I also get the metallic sound at the valve cover and head. That’s why this has been so confusing to me. Chasing the sound back to the injection pump is very much attenuated. So it’s not the IP, and that’s why I was thinking that if it were the injector, I’d hear it in the hard line.

 

[Chris142]

Agree but I had the injectors refurbished and pop/balanced a few thousand miles ago.



When I bought the car the person selling it said it was lifters. These engines are known for occasional collapsed lifters.

#1. Parts can fail any time.

#2. I would not take anyones word for it. If it was mine I would leave it alone.

 

[JHZR2]

#1. Parts can fail any time.

#2. I would not take anyones word for it. If it was mine I would leave it alone.

For #1, the noise didn’t change before and after rebuild. Maybe the injector pops and flows fine but is noisy for some other reason?

For #2, that’s what I’m frustrated about. I didn’t take their word for it, I tested the lifters twice and didn’t see any collapsed. But I changed them anyway because I don’t like the sound I’m hearing. It’s quite loud and has a metallic ring to it. I don’t want something to fail. My real fear was that somehow the cam was hitting part of the lifter system and actually hitting hard enough to make that sound.

I would really like to get rid of the annoying sound.

It should sound more like this:


To me that’s a big difference.

 

[KrisZ]

I could hear the metallic sound in the video and I think it’s way to loud for it to be an injector, especially since the sound propagates throughout other components, like the valve cover and fuel lines.

When the engine is revved up, does it affect the sound? I’m thinking the cam could be rocking in the caps, or at least one of them.

 

[Trav]

Do you know at what psi the injectors pop at? When chasing a noise down like this it is good practice (lets say mandatory) to measure the cam bearings and cam lobes, looks good doesnt really tell the actual lobe size. It seems like you are back to square one only with some new lifters that didn't do anything for it and that sucks. If it was me and the noise appears to come from #1 swap the injector with a new one.

 

[JHZR2]

Honestly that sounds more like injector/combustion noise to me.

How are the injectors? Sounds like an injector overfueling and causing a detonation knock. You can put a stethoscope on each line to hear the difference

Do you know at what psi the injectors pop at? When chasing a noise down like this it is good practice (lets say mandatory) to measure the cam bearings and cam lobes, looks good doesnt really tell the actual lobe size. It seems like you are back to square one only with some new lifters that didn't do anything for it and that sucks. If it was me and the noise appears to come from #1 swap the injector with a new one.

The injectors are 135bar units. They were popped and balanced a few thousand miles ago by a reputable shop and member of the MB diesel community. It seems plausible that it pops and sprays properly in the semi-static conditions of that testing, yet is noisy in use. Seems that’s the case.

I only realized very recently that the injectors in my 603.97 are the same as in this car’s 602.96 engine. I’ve been wanting to get the 603 engine injectors pop tested and balanced, so I pulled them recently. Today after work I installed one in the injector that I thought was the noisiest with the stethoscope.

And. Voila!



Sounds just about right. I do hear some knocking when there’s a very light throttle or the engine is coming back down, and I try to hold it there. In practice in around town driving I did, it’s not really noticable.

So, all that hassle and speculation for that! And yet if I had started with the injector, it probably would’ve been something else and I would’ve wasted time anyway… I can’t win with this stuff.

The noisy injector looked perfect.

Thanks for all the help!

Now that one used lifter is going to bug me forever!

 

[Chris142]

The injectors are 135bar units. They were popped and balanced a few thousand miles ago by a reputable shop and member of the MB diesel community. It seems plausible that it pops and sprays properly in the semi-static conditions of that testing, yet is noisy in use. Seems that’s the case.

I only realized very recently that the injectors in my 603.97 are the same as in this car’s 602.96 engine. I’ve been wanting to get the 603 engine injectors pop tested and balanced, so I pulled them recently. Today after work I installed one in the injector that I thought was the noisiest with the stethoscope.

And. Voila!



Sounds just about right. I do hear some knocking when there’s a very light throttle or the engine is coming back down, and I try to hold it there. In practice in around town driving I did, it’s not really noticable.

So, all that hassle and speculation for that! And yet if I had started with the injector, it probably would’ve been something else and I would’ve wasted time anyway… I can’t win with this stuff.

The noisy injector looked perfect.

View attachment 222998
Thanks for all the help!

Now that one used lifter is going to bug me forever!

Next time post up a video before tearing something apart!

 

[JHZR2]

Next time post up a video before tearing something apart!

I did! I had a few.

Assessing Hydraulic Lifters

My 91 300D has a tap at fast idle. It runs beautifully smooth and strong. When I bought it the PO said that a diesel shop said it may need a lifter. I don’t know that it’s true, but they are known to go bad on these engines after high mileage. I pulled injectors for refurbishment, and needed...

bobistheoilguy.com

Thanks for keeping after the injection noise angle. I had written that off since after all, I had refurbished injectors!

 

[mattd]

The injectors are 135bar units. They were popped and balanced a few thousand miles ago by a reputable shop and member of the MB diesel community. It seems plausible that it pops and sprays properly in the semi-static conditions of that testing, yet is noisy in use. Seems that’s the case.

I only realized very recently that the injectors in my 603.97 are the same as in this car’s 602.96 engine. I’ve been wanting to get the 603 engine injectors pop tested and balanced, so I pulled them recently. Today after work I installed one in the injector that I thought was the noisiest with the stethoscope.

And. Voila!



Sounds just about right. I do hear some knocking when there’s a very light throttle or the engine is coming back down, and I try to hold it there. In practice in around town driving I did, it’s not really noticable.

So, all that hassle and speculation for that! And yet if I had started with the injector, it probably would’ve been something else and I would’ve wasted time anyway… I can’t win with this stuff.

The noisy injector looked perfect.

View attachment 222998
Thanks for all the help!

Now that one used lifter is going to bug me forever!

Glad you figured it out. Next time as Chris said post a video before tearing something apart

 

[KrisZ]

I didn’t know injectors can make such loud metal on metal noises. Good diagnosis by the bitog a-team.