I took my cylinder head off my 89 2.6L 190E. I took it off per the instructions one of my friends got me at his work, lining up the timing marks on the sprocket and the Cam. Off comes the head, and the first cylinder is about halway up. My owners manual says it's 9 DBTDC. Is that 9 degrees back from top dead center? I marked the crank pulley so I can put it back how it came off. I've been cleaning everything out while the head has been at the machine shop. So can you zero everything out when putting the engine back together? What parts get sealant? It looks like there was some on the head gasket. The intake and exhaust gaskets were rather dry, so I couldn't tell if or when they had sealant. The instructions didn't say anything about application of gasket sealant in the assembly section. Does anything get sealant?

> Off comes the head, and the first cylinder is about halway up.

Doesn't sound right. At TDC the #1 piston crown is pretty much flush with the block deck.

> My owners manual says it's 9 DBTDC. Is that 9 degrees back
> from top dead center?

9-degrees BTDC is 9-degrees before top dead center. Usually in crank degrees.

That's probably an ignition timing number which has nothing to do with cam timing for the purposes of removing and refitting the head.

> I marked the crank pulley so I can put it back how it came off.

Why did you take it off?

What for did you mark it? There's a key between the crank snout and the pulley. There's also a pointer on the timing chain cover and corresponding graduations on the pulley.

> So can you zero everything out when putting the engine back
> together?

Did you turn the crank while the head was off?

Is the cam sprocket tied to the chain so you don't lose the chain-sprocket relationship?

> What parts get sealant?

Depends on what you took off but basically only the vertical surfaces of the top timing chain cover/distributor housing that meet the head, and a dab where the ends of the horseshoe gasket meet the head.

> It looks like there was some on the head gasket.

The factory doesn't use sealant per se but there might be a coating on the head gasket that acts as a sealant. Usually the head gasket comes off pretty cleanly. Minimal scraping preps the block deck for a new gasket.

> The intake and exhaust gaskets were rather dry, so I couldn't
> tell if or when they had sealant.

No sealant for either manifold gasket.

> The instructions didn't say anything about application of gasket
> sealant in the assembly section. Does anything get sealant?

As mentioned above.

Sixto
95 S420
87 300SDL

9 degrees before top dead center. 9 more degrees of rotation and you will be straight up and your #1 piston will be all the up. The ½ way up as you described doesn’t sound right to me, ½ way up is 90 degrees or the 9 o’clock position.
Usually people set the motor to TDC for this kind of stuff, but setting it at the timing mark is good too. I'm guessing 9 degrees is the oem ign timing? What’s really important is you put the cam and distributor in the right spot after it’s all over. A digital pix of cam sprocket and head while at TDC is a great idea for reference, sometimes it’s hard to remember exactly how it was, especially after a mill job.
As far as sealant goes, if the doesn't say to then it's probably fine, but someone with more experience may suggest a dab here or there. I always use at least some in and around the holes in the head gasket that water is in contact with, basically making the gasket waterproof at that spot. The closest I’ve come to your motor is a head gasket change on an ’85 190E 2.3L 8V.

I remember tightening the head bolts on my car was scary to say the least, I thought for sure the instructions were wrong. Good luck with it.

There's also call for a dab of sealant on the threads of the bolt that goes through the long arm of the belt tensioner bracket and into the timing chain cover.

Sixto
95 S420
87 300SDL

In my opinion you really should index both valve and ignition timing with the number one piston at TDC on it's compression stroke any other method is sure too complicated for me. With the head off you will have to do this by the correct position of the other pistons with no.1 at TDC to determine if you are on compression stroke or intake stroke. . with the head on TDC on compression stroke can be found by several easy methods.........

William Rogers.........

Good advice in general but the distributor in an M103 is fixed so you can't adjust ignition timing mechanically.

Sixto
95 S420
87 300SDL

Sixto, That sounds like a much better inovation than than a talking center consol that give you stock market tips on your way to work.

Even though I love tearing into my MB's I guess I still think like an old small block tuner.....

William Rogers.........

I took the head off because of it running rough, and a tapping sound. Turns out a cam lobe was severly worn. WIth all these answers I'm a little confused. I took everything off with the timing mark on the cam lined up per the instructions. Everything is paint markered. I think there is two timing marks on the cam. Is one TDC? Did I take everything off with the oppisite mark lined up? So am I good just to line it up with the other mark on the cam and set the 1st cylinder to TDC? I have the position marked on the crank with paint marker. I've rotated it since removal to clean the pistons and everything else. So I can put it on the way I took it off. But I'd rather just set everything at TDC and call it a day. Would make me feel a lot better. Thanks for the advice, guys.

I'm doing the exact same thing on my 190E and I didn't mark anything at all because I found factory stamped marks on all necessary parts, there were also marks from previous jobs, but since this is an engine and any type of mark you manage to put on it is bound to get wiped accidentally I stick with factory marks. I found clear marks on the crankshaft pulley, camshaft, and distributor, anything else needed?

My head is going in for some work tomorrow.

Perhaps we can both share a little of what we learn and in doing so keep our cars running longer and happier.

xp

__________________
1985 190E 2.3L - a constant project.

Your problem is that if you line up the marks you made if you have turned the engine over you you will not know if you TDC compression stroke or TDC intake stroke. And the only way I can think of with the head off is to look at the fireing order turn the engine untill you figure out the math so to speak.Someone here should know where the other pistons are wnen no 1 is at TCD on compression stroke on a 2.6

Then reinstall you head put the cam sproket on its marks and roll a new chain in .You will be able now to check and double check the TDC indicator on the crank the marks on the cam sproket and cam tower TDC on compression stroke on no1 and check the opening and closing of the valve so that they are closed on no1 at TDC and the intake valve will start to open on the next cylinder in the fireing order as no 1 passes TDC and starts down on its fireing stroke.if anyone can make this clearer or if I have missed something I hope you can let us know...........

William Rogers........

william:
I'm not familiar with the details on this specific motor, how would the bottom end know which TDC it's at? I assumed the distributer was cam driven , but then sixto said the distributor was fixed, so I'm not sure what the deal is here.

Larz:
You kinda lost me on that last post. When all is lost, there should be factory markings you can rely on like xp190 found on his. Normally it's as easy as putting the crank and cam sprockets at 12 o'clock. If you can't see your crank sprocket then zero degrees on the balancer should be the same thing. On most engines I've done, the cam would fit on the chain more or less straight up, one tooth either way and it was obviously wrong. The cam lobes for the #1 hole should be away from their corresponding valves. From this point you should turn the crank by hand and see the exhaust lobe at peak lift about 240 degrees, or 2/3rds of a turn. If so you’re lookin good. Turn the crank around a total of two times and stop at TDC and the cam should be back to the correct spot again. Too bad you don’t have a good book with fifty pictures of this whole deal.

The distributor rotor is drive off the cam sprocket. The distributor cap bolts directly to the upper timing chain cover with no means of physical adjustment. An rpm sensor on the flywheel and maybe an rpm sensor on the crank pulley as well send/s a signal to the ignition control module (EZL?).

Sixto
95 S420
87 300SDL

Oic, a crank trigger setup. The original setup on my '80 BMW was like that, but still adjustable. So either way I guess it doesn't matter, TDC is TDC when the head's off. Thanks.