M104 Head Gasket Replacement
 

Hey guys,

My first post on this forum ...

I just bought a 1993 300e 2.8 M104 engine ....the car is in the need of a head gasket replacement and i am in the middle of the job.

I took most of it apart and i am ready to take off the chain to remove the head..

2 problems:

1-I am having a hard-time determining accurately the location of TDC. my car has a bit different indicator on the Crank since i don't have a front TDC center, and the MB CD shows the location of TDC with a sensor...

2-When i rotated the engine to where the TDC is supposed to be, i think that the cams (holes) are a bit off. they are not on the level of the cylinder head as shown by the MB CD. so is this normal? i want to mark the chain before i remove the tensioner and the head ..so i am a bit confused....am i missing something?

see the pictures

the closest to TDC i could get it: the 0IT mark is in the center of the circle

http://img30.imageshack.us/img30/501...ogress2046.jpg http://img30.imageshack.us/img30/eng...jpg/1/w800.png

the locations of the holes in the cams are not level with the head surface as the should be ....
http://img196.imageshack.us/img196/6...ogress2048.jpg http://img196.imageshack.us/img196/e...jpg/1/w640.png

http://img196.imageshack.us/img196/8...ogress2047.jpg http://img196.imageshack.us/img196/e...jpg/1/w640.png

what is wrong? has the car skipped a tooth or something? this is how it currently stands and i want to mark the chains so that i could take it apart. i think it has had a head gasket done before since there is some paing on the cams and the chain, but the don't align properly ....

Opinions needed please!

thanks,

latief

Insert the dipstick into the cylinder hole and rotate the crank until the dipstick is at TDC, then look at the marks. You should be very close after doing this.

thanks,

what dipstick?

I'm assuming the car ran okay (besides the leaking gasket) prior to your project. So, it's probably in time now. Not sure if it's a fact but I've heard the M103s and 104s can run being a tooth off.

Now, I may be quite wrong, as I've never been into an M104 but I think the mark (TDC) on the balancer that you have in the center of the opening for the sensor, should actually be aligned with the bent tab just in front of it. The marks are a visual guide for the tech, which would be hidden from view if the sensor was in place. The sensor itself doesn't rely on the marks per se'.

Try lining it up with that tang and see if the drill bit or dowel you use in the sprocket holes line up right with the casting. BUT, like I said, I'm not sure, hopefully someone who really knows will verify this or tell you the right way.

Now that I'm thinking of it, I believe there is a simple but important procedure for proper cam timing when doing an M104 and it's a common mistake for first timers. Lining up all the marks is not enough, there an extra step involved. I think if you don't proceed correctly, the car will run okay when you're done but may set off timing trouble codes. You should really find out about it from someone who's done a few before you continue.

that's what i originally did, aligned it with the metal tab, but the cam was off on both sides. the closest i could get the holes in the cam to align with the surface of the head was when the TDC marking was in the center of the circle. this model year does not have a front TDC sensor (at least not in that location), and the shape of the pointer i have is different than the picture in the factory CD.

The car was running fine. this is the original timing, i have not loosened up the chain yet, i am just not sure if it should be like this when i replace the gasket, or is the timing off in its current condition???

confusing...

you have to retard the timing on the intake cam. that is the step you are taking about, i am not sure how to do that since i am still taking this apart...maybe some guys could provide some feedback on how to do that ...

thanks,

Look here. http://www.peachparts.com/Wikka/M104HeadGasket

On the home page of this website under the resources tab is a wealth of DIY articles. Mark

like this:

yeah, that was what i am talking about, the pointer (the whole metal tab) in my picture is completely different, and i don't have a pointer per-say similar to that in the picture.....:confused:

I have the article (this guy's shop is a mile away from my house in gainesville, fl)....anyhow, he is assembling the head, and i am still taking it apart. my only concern now is to find the exact TDC before i mark the chains and take off the head !

I worked for them for a spell in the 80's. Good shop and good people. Mark

Just coming back to note that I checked my Haynes manual and the timing mark/sensor bracket pictured there for the M104 is the same as in the picture that hirnbeiss posted. As you say, yours is different. The one in your picture is the same style as the one on my M103 (91 300E 2.6). The TDC mark on mine lines up with that tab at top dead center. The only difference on mine is that the tab lays over top of the marks on crank (the bracket is the same but my crank markings are either wider or the crank sits deeper).

In your pictures, it appears that the cam gear marks wouldn't line up right no matter where your crank was and that is kind of strange. As you said, you want to find TDC on the crank so you can understand better what's up with the cams. I think what gmercoleza was suggesting was that you put the oil dipstick down the spark plug hole, turn the crank and observe when it's at its highest point. It should be pretty close to TDC, then look and see where your timing marks are. It apppears by the presence of red rtv on the timing cover that it has been apart before. Anything could have been messed with. You may have to set it up again from scratch, but again, I really don't know. How you proceed from there is something I wouldn't want to make suggestions about at this point given my lack of familiarity with the M104 and variable valve timing.
Good luck, please post how it works out.

including a timing poiter from the junk yard or being a tooth off of one or both cams

The oil level dipstick - insert it into the spark plug hole and use it to find TDC, then check out your marks.

Well i think that this has something to do with either how the m104 is supposed to be timed, or a poor head gasket job. the engine runs smooth as butter so at least i am confident there is no valve damage......i reset the engine to TDC using the tab, now one of the holes aligns perfectly with the surface of the head as it should, the other one is slightly off. so i think i will take it apart tomorrow and see where everything stands... some people (on the other forum) suggested that my chain might be a bit looser than it should but i doubt it as it is tight as it could be...

I will keep this post updated, i am open for ideas and opinions !!!