I need some specs if anyone has them.

Some of you may remember that roughly a year ago I completely rebuilt and tuned the CIS-E system on my 1992 300E 3.0 with 210k miles. Since then it has run quite well, averaging about 22.5 MPG in the city and up to 26 MP US gallon on the highway at just over sea level. I have noticed that the oil consumption has been about a quart per tank of gas and knew that I would have to get the head off at some point to fix that.

A sudden drop in mileage forced the issue. I had to pull the O2 sensor (Bosch 13953 is the inexpensive replacement if you can solder the OE connector on yourself) that was new a year ago and torch it to get it working, though not perfectly, again. Oil contamination killed it until I brought it back from the dead. I have a new one, but did not want to put it on until I had the head repaired. Fuel mileage got better, but was not back to what it was a couple months ago.

Notes on head removal:

I did NOT remove the intake manifold

If you can remove the exhaust manifold to head STUDS along with the nuts, you can leave the exhaust manifolds in place. Don't forget the Allen screw at the back of the head that attaches the EGR tube.

Leave the cam gear in place, just unscrew it from the cam and note the position of a couple cam lobes. This will put the car right back at pre head removal cam timing when you just bolt the cam back in. NOTE: You will need to remove the Timing Chain Tensioner SPRING before you pull the gear off the cam. You will need a 12 mm Allen wrench (or better, socket) to remove the cap (passenger side of the front of motor) to get to the spring. If you forget to do this, the plunger (feeds one way only) will tension the chain and you will not beable to get the gear back on the cam at reassembly. You can solve this problem by removing the tensioner (17 mm Allen wrench) and popping the inner plunger through the outer plunger and then feeding it right back in the other side. If the chain has forced the tensioner arm down, you can carefully pry it back so you can reinstall the tensioner all the way in.

IMPORTANT Remove the locating pin for the plastic timing chain guide by screwing in an M6 bolt about five turns and then wiggle/pull the pin out of the head.

I pulled the cam out of the head before I removed it to make the head lighter. Watch out for the little shim/cups that sit between the rockers and the top of the valves and the crescent shaped spacer in the front of the head.

The intake valve seals were hard as a rock.

Notes on machine work:

It took about 0.003” of surfacing to get the head flat. There was a slight dip in the middle on the exhaust side.
Valve to guide clearances were about 0.0015 on the exhaust side and 0.001 on the intake side. I note this because I have read several posts about replacing the valve guides. I do not have the specs, but this kind of clearance on 8 and 9 mm valves with over 200k miles suggests very little or no wear.
Two of the exhaust seats were still perfectly concentric, two came in after feeding down 0.0012, one took about 0.003 and the worst one took 0.0044. I took them all down 0.0012 beyond the initial cleanup. By the way, my Newen G2 is for sale if anyone is interested.
I need a new pilot for the intake side, so I’ll have those numbers in a week. EDIT The intake seats had moved quite a bit more than the exhaust seats. Two required 0.014" to bring concentricity back. How much this changed my balance for compression ratios, I did not bother to calculate since this is a commuter. You performance guys might want to check all the combustion chamber volumes and then match them to each cylinder so you end up with balanced compression ratios.

Parts I will replace:

1. Valve Cover Gasket
2. ALL Valve Stem Seals
3. Timing Cover Seal Strip (103 015 02 20) This one was very brittle and there were obvious signs of oil leaking where the seal met the head
4. Head Gasket
5. Valve cover to intake manifold breather tube. Also hard as a rock.

So really very inexpensive.


While I am waiting for my intake pilot, can someone please tell me the valve to valve guide clearance specs. I do NOT want the wiggle test specs, though I can do the math to back into the clearance specs if that is all MB lists.
Thanks!!!

At 200k take the opportunity to check the bearing bracket that holds the fan clutch. If its never been replaced, you'll likely find quite some play and if you do, get her replaced now since it'll take 10mins to do it. The fan clutch should have no play and spin perfectly straight.

Glad to hear you left the intake manifold alone -- its just sooo much easier for the sake of less potential headaches.

How do your timing chain guides look?

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

"How do your timing chain guides look?"

Educate me. How should they look?
and
How did you check for play in the bearing bracket?

Keep in mind, I left all of that on the front of the motor. There is no play in the fan at all side to side, though I can slightly move it forward and backward. There is no wear on the cam sprocket and the chain just barely lifts off of one tooth when I try to pull it away from the sprocket.

Still need valve to guide clearances. Anyone?

Unsure on clearances, sorry.

Well here is how mine looked at ~85k cant remember exact mileage I did it the first time, and I left them alone. A little wear, but I still see another 150k out of them and I expect to have to pull the lower front cover off eventually to reseal so I will do it then.


What head gasket set did you buy?
Just my experience -- I had victor-reinz and followed factory instructions -- 10k later oil was leaking out of gasket at rear corner. I ended up pulling the head AGAIN, but this time noticed that the Victor-Reinz MANUAL states 70nm instead of the the MB stated 55nm, so I did it to 70nm...Its been 15k since then and no usage so far.

Not sure if it was just a bad gasket, or whether the 70nm helped, but just a heads up for you to think about.

As for bearing bracket. It'll be obvious. Just grab the fan clutch and jiggle it...if it moves I would get it done. Easiest way is with the car running. You'll see if its spinning straight or has some movement as it rotates, but since you have the car apart you won't be able to do that right now, but grabbing it should be good enough.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Robert,

55 Nm (40+- ft*lbs) is not nearly enough for these head bolts. Even 70 Nm (51+- ft*lbs) is only the first step. You needed to go back and do two more 1/4 turn on each bolt. Perhaps you did that as well, it just was not clear to me in your post. Yes, I have the same VR head gasket. A bit of extra RTV at the joint between the head gasket and the front cover seal (Timing Cover Seal Strip) may also be prudent. I have read that MB beefed up their head gaskets at this junction.

Based on the amount of chain I see above the guide and the uniformity of what I see as the chain goes down and out of sight, and the amount of material I see at the end of the guide, it seems as though I have less wear than you. The previous owner did about $13k of service work in the last 50k miles so perhaps this was done.

A few years later, here is the update. The oil consumption was still there, so the new stem seals were not the panacea. I now know why. One of the kids hit something and put a hole in the pan. I now have a bottom end with more bearing material in the pan than around the crank main and rod journals, though the crank still turns. I found a running junkyard motor and later found that one cylinder did not leak down well. Oh well, two to make one.

Here is the takeaway: ALL 12 cylinders are missing crosshatch in rather large patches up, down, and around the bores. Inside bore gauge and mic showed 0.002x-0.003x piston to wall clearances yet we were able to slide a piston down the bore with a 0.004 slider gauge (no rings, of course).

M103 Bottom End Rebuild topic coming soon.

Sucks...I have had basically zero oil consumption since I did my rebuild in 2009 up until about 6 months ago and now I am burning about a 1qt every 2k miles. Likely the stem seals are toast again after almost 100k as a few of my plugs have a lot of carbon build up on them (had I known victor-reinz was trash 7 years ago I wouldn't have used it!)

I'll be doing that job again soon after I replace the tumbler flap on the intake manifold on my M272. Once that's done I plan to take some photos for cam wear at 180k with my cam that has NOT been replaced with the hardened version. Will be interesting to see what wear it has after using 15-40 diesel oil almost its entire life.

__________________
2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k