Welcome to the forum. Wow, interesting to see it open like that.

Can I recommend putting vehicle model and year into your profile for us please? It's helpful 👍

Complete your Profile

Click on ACCOUNT SETTINGS, and scroll down to 'Vehicle Details' , and Location, then click 'Save' on bottom. At least a State would be good, and will show when a member hovers his cursor (arrow) over the flag next to your post.

www.benzworld.org

 

Okay, I put that in my profile.

I found the answers to most of my questions in the WIS. I didn't find any info on how to remove the black plastic chain guide from the head.
I already knew about this problem before I opened everything up and wanted to leave the old plastic guide in place. Now I discovered that it is damaged.

Does somebody know how to remove this guide from the head or knows the WIS document name describing that?

I can't find a document in WIS where they talk about this guide.

It doesn't seem to be an ordinary screw holding the guide to the head. Maybe the bolt is pressed into the head and I need a special tool to remove it.

There is an inside thread. On the backside of the head there is nothing visible. So I don't know how to remove this pin holding the guide.

 

That pin is friction fit. It gets removed with threaded tool.

 

oh, thanks!
So I was trying to figure out to remove this thing. I saw different tools online for MB engines to remove those pins, but not for the M278.
So that's what I did:

thread a bolt in there
put a socket on it
and a nut

tighten the nut

And the nut will pull it out.

works like a charme

 

That's how the thing looks timed. The actual timing procedure what pretty straight forward. Most of the work was moving the heads and taking the camshafts off. I thought that I might be able to do it with the cylinder heads and camshafts in the place. But it is not possible, heads and then from the heads the camshafts need to be removed.
That is also why I took the engine out, it is easier like that to work on it. Also the oil pump needs to come out and all that is easier with the engine removed.

There is not that much info out there for the timing marks so here they are.

crank sprocket

middle sprocket
on top chain coming from the crank sprocket
on the bottom passenger side timing chain
The driver side timing chain marks are at the rear of the sprocket and not visible.

driver side head

intake camshaft

exhaust camshaft

passenger side head

exhaust camshaft

intake camshaft

 

The upper timing chains have three yellow marks.
one for each camshaft and one for the crank
the lower chain has two yellow marks
The sprockets have also yellow marks, if they are faded they have a punched in dot.

line up the crank mark from the driver side head with the middle sprocket at the rear of it
mark the marks with whiteout for better visibility
You can twist the sprocket a bit to check the marks.

line up the chain going from the crank sprocket to the middle sprocket

line up the crank mark for the passenger side head

with the camshafts loose, rotate the camshafts in position to their marks
The camshafts have laser marks.

bolt down the camshafts

install tensioners
if necessary move the metal guide with a medium sized pry bar a bit forward to make space for the tensioner

 

Okay, all of that is back in the car and driven for some time! no timing codes anymore!
It has a code for the intakte manifold pressure sensor. So I am going to take the intake out at some point and put a new sensor in.

 

Thanks for this post, I'm facing the same issue with the metal tensioning rail. Can't figure out how to replace them without removing the head. To remove the head, WIS says to remove the engine which is not practical in my home shop, the way WIS says to do it, since I don't have a lift.

How did you remove the engine? Did you drop the subframe and pull everything out from below like WIS says?

 

I removed the bumper, front end, wiper cowl, and plastic covers between engine and firewall. That gives enough space to pull the engine out to the top. Under the car you need to remove the exhaust bolts, transmission-engine bolts, starter bolts, torque converter bolts, engine mount bolts.
I didn't find suitable mounting points to attach a chain on the top. I wrapped two straps around the engine and pulled it out with an engine hoist.

If you have any questions, I can try to answer them. I also have around fifty pictures of the engine in various states.

If you want to do the job right, you need to move the heads.
You can also just replace the chain and leave the old guides in the car. They sell the chain open. You remove a piece of the old chain, pull the new chain in and close it.

It took me around two weeks (eight hours a day) to remove the engine, move the heads, clean everything, put it back together.

 

Thanks, this is very helpful.

I wasn't planning on replacing the timing chain tensioning rail, because I don't want to lift the heads, but the plastic tip is broken off on the right side. Can't figure out how to remove the rail without removing the head and I really don't want to tackle that on my own.

So, I think I will replace all the parts I can and button up everything and take it to a dealer to replace the rail.

I'm also wondering how much the plastic tip really matters and whether or not it is necessary to replace the rail.

Here's a close up of the broken tip:

Here's a pic of what it should look like:

 

If the tip is broken, there is probably further damage to the guide and the whole plastic might come apart.
This is the passenger side which is good. The driver side guide is further back. I think I might have removed this guide before moving the head, to see if it is possible. The driver side guide is much harder and maybe impossible to remove without the head off. In any case I wanted to do the job right and moved the heads.

Maybe you can take the pin/screw out holding the guide like that. You can turn it with a wrench at the bottom. Maybe you need to bend the wrench.

Maybe you can do something similar for reassembly. There are more MB engines where you need to remove the heads for the timing guides. For this other engine type this guy came up with this procedure. He breaks the plastic guide and then shortens the pin/screw a bit to put it back. You can see him
breaking the guide at around 11:50.
Maybe this video will give you some ideas.

The M278 engine is prone for cylinder wall damage. You might want to check for cylinder walls with a borescope before spending a lot of money on it at the dealer. And it will be a lot of money. If you are in my area, I might even be able to do it for you.

If you decided to do it yourself, I could help you along the way. It is very complicated in my opinion though. The camshafts need to be removed too. chance of error when putting them back

 

Thanks for all your help, it is great to have someone to talk with who has actually done this repair! I'm in the Atlanta area by the way, where are you located?

As for the video, I'm actually trying to remove the metal timing chain tensioning rail rather than the plastic guide so breaking it isn't possible. I saw one of your pictures where you had the rail removed with the head still on (see below) and I would love to know how you did that.

My plastic guides still look good so I could leave them if I can figure out how to remove/replace the passenger side metail guide rail.

Many thanks!

 

Ah, see, my memory was correct, I did play with that before removing the head!

This screw with the yellow circle holds the metal guide. It has a top like a pin, this top sticks into the guide and holds it. Below it has a collar to put a wrench on it. Below that is a thread that is screwed into the head.
To take this out, you reach behind the metal guide with a wrench. Put the wrench on the collar on the screw, turn it and remove it! You might have to bend the guide a bit to make it come out.

As for the video, I'm actually trying to remove the metal timing chain tensioning rail rather than the plastic guide so breaking it isn't possible

I know. I sent you the video for the reassembly. Maybe you can shorten the screw's thread a bit like he does in the video so you don't have to bend the the new guide.

I am not sure if you will be able to remove the chain with the guide once you removed the guide from the head. I think the chain will not pass between head and camshaft. You will either have to open the chain (I can tell you how) or remove the camshafts or the camshaft adjusters.

I am around 500 miles from Atlanta.

 

Thanks. I’ll give that a try. I already have the cams out but have the tools to open the chain if necessary.

 

Oh, wow, you have them out already! When you get to reinstalling the camshafts, you might want to be extra careful! They are held down by these roundish bronze-colored pieces. When I tightened the bolts holding these pieces, the bolts bent! They didn't have enough strength to push the camshafts down.
I got new bolts and managed to get them down at some point, but I wanted to make sure they were in a good position.
I got cylinder head covers from another vehicle and cut four holes in it.

With those special tools I pressed the camshafts down. Through the cut out holes I then tightened the four screws. I removed those cylinder head covers and put the undamaged ones on later that belonged to the car.

I took some pictures from the actual procedure but don't find them anymore. If you at some point feel that you could need my special cylinder head cover tools, I could send them to you.

In any case take good care when installing the camshafts and make sure they are bolted down good.

Maybe there is no need for all this. Maybe you can put the camshafts just in positiok somehow and the cylinder head cover will press them down later for good. But then maybe the little four screws will come loose inside. I didn't want to take any risks and came up with the above.

 

I took some pictures from the actual procedure but don't find them anymore.

I went through my phone today and came across the pictures of how I tightened the cam bearing caps with the cut out cylinder head covers.

 

Very creative! I hope I don't have to do that, but we'll see. I had to reinstall the camshaft keepers at one point for some reason I don't recall and I just rotated the engine a bit to relieve the valve pressure enough to snug them down, but I wasn't concerned about where the timing marks were when I did that. Might be harder when everything is all lined up.

 

Tighten all the cam bearing caps at the same time, evenly, a little bit at a time and it should go together fine.

 

Okay, I finally got the right tensioning rail off without bending it or removing the head, and I have installed the new one the same way. Thanks for all of your help on that part!

My car was throwing a P0016 code (bank 1, sensor A) and the intake cam adjuster was off by one tooth when I opened the case. The left bank marks are in sync with the chain at 40 degrees TDC, so the problem seems to be isolated to the right bank being off by one tooth. Which was probably caused by the broken tensioning rail that I am replacing.

To be safe, I've replaced both cam adjusters, the secondary timing chain, the broken tensioning rail, and the tensioner on the right bank. The rest of the parts look great so I'm trying to reuse the bottom gears, the primary timing chain, and the left bank chain, guide, and tensioning rail. I am replacing the left side and bottom tensioners just to reduce rattle.

So now, I'm trying to time the engine but I can't get the top and bottom yellow marks to line up. I still have the right bank chain off the gear so I'm only trying to line up the left bank with the bottom marks before reinstalling the right bank stuff. I've spun the engine 100+ times and can't get the left bank cam marks to line up with the bottom gear/chain marks.

I thought about lining up the bottom marks and then repositioning the left side chain and cams, but I don't think I have enough room behind the main bottom gear to advance the secondary chain over the sprocket to get things all lined up. I would pull the gears out and do it if I could, but I can't figure out how to remove the oil pump tensioner and chain without dropping the oil pan and I don't want the hassle of doing that with the engine in the car.

So, any advice you have will be greatly appreciated. It seems like I could spin the engine forever right now and not get the left bank marks to line up with the bottom gears/chains.

Thanks!!!!

 

I am not sure what you are trying to do.

If you try to check if the timing is correct by turning the engine over until all the marks line up again:
I had to spin the engine around 250 times. It takes a long time for the marks to line up again. But they will if you did everything correctly. Take your time, of course with the spark plugs or the injectors removed, and keep spinning.

 

How did you drop the A/C Compressor without pulling the engine? I can see from your first picture that you did but I can't figure out how to get to the back bolt. The front bolts are easy but the back one seems nearly impossible with the engine still in the car.

I'm trying to reinstall the timing case cover, which is a tight fit, and the compressor seems to be in the way.

 

I don't remember having any problems with the ac compressor.

Maybe your engine mounts are gone and your engine sits further down. Maybe jacking up the engine will help.
Maybe you are not looking for the right bolt. I don't know, I remember it to be straight forward.

I also remember damaging the head gasket when installing the timing cover. Try to keep the head gasket straight. If you damaged it, it wouldn't be a big deal though.

 

Yeah, I'm really struggling trying to get the timing cover back on with the engine in the car. I didn't drop the oil pan so it's a tight fit. I've practiced several times before putting gasket sealant on to make sure I can do it quickly before things dry but haven't mastered it yet so I thought I would drop the A/C compressor. I might try jacking up the engine to see if that helps.

 

Did you get the compressor back on and maybe also put the whole car back together?

 

Hi Das. How were you able to get the timing cover off with the motor in the car with the oil pan and heads on? I'm trying to replace the infamous oil/water seal on the inside of the timing cover as well as all of my coolant turbo lines and water pump. I've removed all turbo coolant lines, water pump, oil cooler, alternator and a/c is disconnect and strapped up on the side and all bolts from the timing cover have been removed including the four that extend downwards from the heads and the group the come through the oil pan on the bottom. Intake manifold and valve covers have not been removed. I've followed direction from alldata. However, I am unable to pry the timing cover away from the block and i'm afraid if I pry any harder, I may break the cover. How did you get yours off? Do I need to fully remove the oil pan? Your first pictures show your oil pan is still on. I really appreciate any advice. Thanks.

 

I pried the timing cover off with a pry bar. Make sure all the bolts are out and it should come out.

To put the timing cover back on, I had to take the oil pan down. Otherwise you will damage the headgaskets that extend out over the block and seal the cover from on top.
So you might just take the oil pan down now because you have to do that anyway later.

 

I see. After looking at your pics, it looks like I need to take the intake manifold off and get the four bolts that are horizontally bolted through the back side. Is that correct? Do these bolt holes hold the timing cover from the other side?

 

PS: I think I had to hold up the bolts that come down from the heads. They will fall back down into the holes if you don't push/pull them up while moving the cover forward.

 

Hi Das, Where do you purchase your headgasket kits and headgasket bolts from? Has anyone had any experience with the M278 gasket kits that are available on e-bay? These are from China but look like factory, some of them even come in mercedes benz boxes.

I also need to get my camshafts repaired or replaced. Has anyone had any experience with reconditioned camshafts? On each of my camshafts I have some lobes that are starting to get wiped out. I guess I caught them early since the motor was running well prior to teardown.

Thanks for the advice.