Head Work 1989 M103 300SE - PeachParts Mercedes-Benz Forum

wbain5280 · #1 06-05-2008, 01:51 AM

My oil consumption is fairly high at around 800 miles per quart. I decided to replace the head gasket and valve stem seals and now have the head off the car.

There are two support brackets under the intake manifold where the manual implies one, or did I misread it.

I'm lucky I've got an engine crane to remove the head with the manifolds. That combination is very heavy.

The spark plug wire are a ***** to get off the plugs and I'm got the official plug boot puller.

I'm going to post some pics of this soon.

mbdoc · #2 06-05-2008, 08:50 AM

Since you have the head OFF, why not fix the problem & have the valve guides replaced??

wbain5280 · #3 06-05-2008, 10:17 AM

MB Doc, fill me in on why the guides need to be replaced.

Here are some initial pics:

Side View

View of the business end.

mbdoc · #4 06-05-2008, 11:11 AM

Excessive wear of the valve guides is very common on M103 engines!
If that engine is burning oil then valve guide seals on a worn-out guide is like a band-aid on a cut that needs stitches.

A good machine shop can check for wear on those guides & replace them and you will have a better engine.

wbain5280 · #5 06-05-2008, 11:30 PM

OK MB DOC, thanks for that explanation. I'll do the measurments myself, I'm in class for that already and have access to the valve guide removal tool, and get a new set.

I was just curious if these were a common wear item at my mileage, about 160K, which it seems they are.

Do you have any recomendations when I remove the valve gear, such as rotating the cam lobes down when I remove the rocker arms?

Thanks for the comments and recomendations.

BTW, I now have the intake manifold off and I'll be replacing the injector holders and seals, the idle bypass hoses. Do you have any other recomendations?

mbdoc · #6 06-06-2008, 08:03 AM

Since the rocker arms unbolt from the head the camshaft isn't under load, the rocker arms & bearings are.

Replace the hose going to the waterpump.
Also the "hoist" bracket at the back of the head has a coolant o-ring that should be replaced.

Ivanerrol · #7 06-06-2008, 08:49 AM

I recently had the seals and valve guides done at 195K's.
While you have the head off why not do it?
If the guides are out of spec they will quickly ruin your new seals anyway.

My pistons looked similar to yours - more worrying for me was the burnt oil smell pervading the cabin.

gmercoleza · #8 06-06-2008, 09:09 AM

Also - if that's green coolant residue I see in the pics, GET RID OF IT!

S-Class Guru · #9 06-06-2008, 04:45 PM

Warren, that brings back some fond memories, I did the head on my '91 SE a few years back. A few of my memories:

I was always told to never put an aluminum head back on a cast iron block without checking/planing it, and to always do a valve job and guides if it had more than 100k miles. I had it done, and it's used zero oil for the last 80k miles. So Doc has excellent advice on that. Plane that head, get it really smooth so it won't chew up the gasket as it slides over it every time the engine heats/cools. That's the main cause of the leaking gaskets, uneven expansion between aluminum and iron, which grinds up the gasket.

Yeah, I think I remember 2 braces under the intake (and the book does show one, but probably just for illustration. Feel free to remove/replace both, HaHa).

No need to turn the cam as the rockers are loosened, as Doc said. Just kinda alternate the bolts as you take them loose.

Might check the motor mounts while they are easily accessible, pretty cheap to replace.

Yeah, ditch that green stuff; the Daimler/Chrysler stuff is readily available at Autozone now, so why not use it. Drain and flush a bit to get all the green out though.

Check the water pipe that goes from the head to the water pump - if it's corroded, you might want to replace it while it's easy to do.

You do know how to reset the chain tensioner I'm sure?

Oil the washers under the head bolts. Otherwise they will gall and not torque down properly. Clean and oil the threads also. That last 90-degree turn on the head bolts was the scariest thing I have ever done on a car engine. I don't know what the torque is, but I was cranking for all I was worth, expecting to snap a bolt at any second.
But, it worked out fine.

You know the three little screws that hold the cam oiler "pipe" on top of the rocker arms? Clean and locktite them (they can & will come loose).

That's all I can remember; but she still uses zero oil and doesn't ooze anything after 6 years, so mission accomplished.

Have fun,
DG

junqueyardjim · #10 06-18-2008, 03:49 PM

Since I am getting ready to replace the head on my M103, I was interested in the pictures. It looks like the timing chain can be removed from the cam gear and the head removed without breaking the chain. I imagine (and it looks like) the chain tensioner has to be removed. If one has it all lined up and well marked, is it a reasonable job? Does that upper chain guide have to be removed also? Is there a really good thread showing head removal on the 103.

S-Class Guru · #11 06-18-2008, 04:46 PM

Yes, you can leave the chain intact; as you said just mark everything carefully to be sure you get it back in proper timing.
The upper chain guide can be left in place, but there is one pin that goes into the head, that will need to be removed. It is pressed in, but threaded internally, so you can screw a bolt into it and use a slide hammer to pop it out. Or, just use a long screw that threads into it, and some kind of heavy weight on the screw to slap it like a slide hammer.
The tensioner will need to come out, pretty easy, just unscrew it. Getting it back in can be a challenge since it's got a pretty strong spring on it.
I fabb'ed a tool from a bolt with the proper size head to use as a hex wrench to get leverage and turn the tensioner cover.
be sure to take the tensioner apart and set it on the loosest notch before reinstalling it - it's obvious when you disassemble it.
Other than that, pretty straightforward. just have the proper 12-point torx for the head bolts; they are really tight.

DG

Hit Man X · #12 06-19-2008, 09:57 PM

The M103 is easy to pull the head, I had one off in about two hours at the parts yard... I bought a spare head to rebuild for my 300SEL so the downtime is minimal.

Also, verify you have the correct style headbolts. Some have washers, some don't

My consumption is around one quart per fill up of 93.

wbain5280 · #13 06-21-2008, 06:44 AM

Yesterday I took the head to the school's shop and removed the valves for cleaning and to check the guides. After cleaning, they all failed the wiggle test. New guides are in order and I have to get a move on, school is over in about a month. I dread the tightening procedure.

wbain5280 · #14 07-15-2008, 01:09 AM

I have the head back together. I had to heat the head to 400 degrees F in the oven and after 25 mins, it was smoking, ie done. The guides came right out. The new exhaust guides went right in and the intake guides were a little harder because the head had cooled off at that point. A little freeze mist helped. I ground the valve faces and seats and installed all stem seals and the exhaust valves. I finished the intake valves at home and now I have to finish the intake manifold, new hoses and injector seals. I'm not looking forward to angle torquing the head.

If anyone is going to do this, keep all parts together in plastic bags, when the engine is at TDC, only two valves are open, cyl 2 and 3, so support the head with some wood strips, I used 1" X 2", and use assembly lube on the cam bearings and lobes. Carefully torque the upper cam bearings to 180 in-lbs, 21 NM, or about 15 ft-lbs. I had some trouble with three of the bolts so I used a 8mm X 1.25 die to fix the threads. I should have used a thread restorer, which rolls the threads, but I don't have any, they are at the school, but it worked fine and the three bolts went in perfectly. I did this because the bolts began to bind and I didn't want to ruin my head.

I'll post some pics once I get them from my camera.