Did the front timing seal and other stuff (M103) - PeachParts Mercedes-Benz Forum

tinypanzer · #1 03-30-2009, 09:53 PM

Wow, what a bunch of work this weekend. I tore into my timing cover on Monday, only to be sidelined by non-stop rain all week. Finally it quit raining Sunday and I was able to finish up.

I wish I had taken pictures along the way, as I had planned to write up the procedure and post it. However, my schedule got so screwed up because of the rain that when I finally had a chance to finish the job, time wouldn't allow pictures too. But, I will do my best to describe, and I will post the finished results here.

Starting with disconnecting the battery and removing the fan shroud, the next thing I had to do was tear open the timing cover, which involved removing the distributor and valve cover. The valve cover is easy, heck it practically falls off by itself anyway. The hardest part about getting the timing cover off is getting that blasted distributor adapter out of the camshaft. I decided that I was going to replace the entire distributor assembly, so I wasn't too worried that I had to destroy the back cover of the cap by prying against it to get the adapter out. A small slide hammer would have been nice for that task. Ultimately, I was able to get it out after several sprays with PB Blaster and patiently prying from two sides simultaneously. Even so, I snapped off one of the tangs from the adapter. I ordered another one for the very reasonable cost of $18. The new one appears much beefier.

The next tricky part was replacing the camshaft seal. I decided to order it from the dealer just to make sure I wasn't going to have to do this part twice. The most important part of this job is getting the old seal out without damaging the hole. I used a large steel peg that just happened to be slightly smaller than the hole, and I was able to bang the seal out fairly easily. I did it with the timing cover removed, and on my bench. I also made sure that the sealing surfaces of the cover were not taking any load from the hammer blows, making sure that little bits of sand or debris didn't gall the metal and ruing the seal.

After knocking the seal out, it was time to clean the cover up. After using a wooden tool to remove all the clumps of old sealant, good old soap and water were used to clean it up. It took a while, but I made sure that the sealing surfaces were immaculately clean, especially on the corners where the cover meets both the lower timing cover and the head. You want to see bare metal here.

Putting the new seal in was pretty easy. Just lay it flat on the hole (making sure the right end is out) and press it in using a small block of wood. I was able to press it in almost flush on the first try using this method. Resist the temptation to push it in that last half a millimeter. Being perfectly parallel is FAR more important than having it flush. The reason the wood will not push it in perfectly flush is that the rubber gives a bit when pushed on. Trust me, it's just fine. It ain't going anywhere.....

Now, you should have already purchased the camshaft seal and the timing cover seal before you started this. You should also have a little tube of the $25 Mercedes sealant. You can use other stuff, but if you have to re-do the seal later on, you'll be kicking yourself for being cheap.

I found out quite by accident that one tube of the MB stuff is exactly enough to redo the front timing seal, the water pump heater tube O-ring, and both sides of the valve cover gasket. I advise getting the new O-ring, the camshaft seal, the timing seal, and the valve cover all at the same time. Then you can kill all of those leaky problem areas in one shot, with one tube of goo, with one tear-down and reassembly.

Now you need to get the timing cover sealing surfaces immaculately clean. After using my fingernails to scrape off what I could, I finished with a plastic gouge and a dental hook for the little crevices. GOOD GOD, BE CAREFUL. DO NOT DROP A TOOL INTO YOUR ENGINE!!! I came perilously close to dropping a Q-tip down there..... What a dilemma that would have been.

After you have cleaned the area well, wipe it with a cloth soaked in brake cleaner to de-grease it. This will really help the sealant work.

Now, if you are ready to go, apply a few dabs of sealant in the corners where the lower timing cover meets the head. After that, do a thin line of sealant in the groove all the way around that bottom timing cover. Then, place the new gasket in there and press it in real good. Now, put the goo on the head on the areas that mate to the top cover, overlapping onto the first part of the gasket, in the corners. It is not necessary nor desirable to put sealant on the top of the gasket except in the corners. The new gasket (starting in '88) has a better pattern and makes a better seal than the original. Besides, the leaky spot has never been this part of the gasket.

Here's the tricky bit - I'm assuming that like me, you don't own the insertion sleeve for the camshaft seal. I was able to get away without one, but it was a bit tricky. First, oil up the camshaft and the seal. Don't use grease, the MB manual warns against that, claiming it will prevent the seal from transporting the oil back inside the engine. I agree.

The hard part is getting that cover back on, while seating the seal, and not smearing up the sealant you just paid $25 for. What I did was use a plastic RETRACTABLE pen with a very smooth, rounded end to go around the inner lip of the camshaft seal and help stretch it over the camshaft as I carefully pushed the cover on. After running the pen around the seal a couple times and wiggling the cover, it went on!

Here's another tricky part, and necessary to get this to seal right. You MUST start with the bottom two bolts for this thing to tighten down correctly. Start by getting both bottom bolts finger tight. Then, go back and forth between the two bottom bolts tightening a half turn each time. It's very critical that they get tightened evenly, or the seal will tend to squish out the wrong way or worse, if you tighten one side before the other, it will pull open the opposite side from the one you just tightened allowing air bubbles into the sealant.

So, after you get the bottom bolts tight, you can do the top bolts. Then go back and snug them all to spec.

Now at this point I had to stop and switch tasks to painting my valve cover. Since I am assuming you are skipping this step, proceed by cleaning up your valve cover, particularly the sealing edge. In fact, I sanded and dremeled my cover down to bare metal on the sealing edge to promote adhesion to the sealant. After getting that edge totally grease and peeling paint free, I ran a bead of MB sealant all the way around the inside of the new valve cover gasket. I then pressed it on to the cover and sure enough a tiny bead of sealant appeared all the way around letting me know that I used just enough.

Now, here's a fun bit. Totally de-grease the valve cover sealing surface of the cylinder head. Pay very close attention to the area in back where the little semi-circle cut out is. This area likes to leak more than any other. Get it completely clean, use a rag with brake cleaner if you want. It's worth the effort.

At this point, you should have exactly enough sealant to go all the way around the head, leaving a nice bead for the valve cover gasket. Put a little extra on the back and by cylinders 5 & 6. Put a little extra in the semi-circle cutout.

Okay, now carefully lower the valve cover onto the head. Start by threading two bolts, one in front, one in back. Now add the rest and start tightening. Do it like you would normally do a valve cover, but realize that as soon as you tighten one set of bolts, the others loosen up. I had to go around at least a dozen times to get everything snug and even.

As luck would have it, I got a beautiful bead of sealant all the way around the whole valve cover. Looks like a did a good job. Pictures coming soon.

Before you put your distributor back on, remove the bolt holding the heater tube to the motor, and pull the tube out of the pump. Replace the O-ring. Dry everything up, and use the last bit of MB goo to fill in the area behind the O-ring. Use a good bit. Shove it in there and tighten it down. Some should ooze out. This is good.

Now, you can put the rest of the stuff back together....

That's if everything goes smooth.

Here are a list of parts you WILL need:

1) Timing cover seal
2) Tube of MB sealant
3) Camshaft seal (why not do this now and save the headache?)
4) Valve Cover Seal
5) Something to de-grease sealing surfaces

Here are a list of parts you may very well wind up needing once you bite in:

1) Distributor cap
2) Rotor
3) Distributor cover
4) Suppressor housing (both parts)
5) Camshaft to rotor adapter
6) Heater tube O-ring
7) Ignition wires (if you break one)
8) Vacuum line (if you break one)

I'll post some pictures of my finished result...... Gotta get my camera from home.

Ferdman · #2 03-31-2009, 08:10 AM

tp, as far as I know valve cover gaskets should be installed dry ... no need for sealant. No doubt the valve cover doesn't leak now, but it may be a problem to remove in the future. When I resealed the upper timing chain cover on a 104 engine I installed the came shaft seal after reinstalling the upper timing chain cover. It's far simpler that way.

tinypanzer · #3 03-31-2009, 07:33 PM

Yes, the valve cover gasket is supposed to be installed dry. However, I have learned that the replacement gaskets available these days get rock hard in less than a year, and they always start leaking at the back of the motor and by cylinder 6. This is my third valve cover gasket in less than a year. The last one leaked so bad that it dripped oil onto the exhaust causing a suffocating plume of smoke in the cabin whenever the Klima is on. I got sick and tired of it and decided to seal it down. I was loosing a half quart of oil per week mostly from the valve cover.

I don't think removing it will be too hard, one could just shove a tool into the half-circle cutout in the back and lift up.

This does bring me to one observation - if you do decide to goop down the valve cover like I did, make sure you are happy with your temperature sensors since you usually have to remove the valve cover to loosen them.

I've never done the cam seal on a M104.

According to the MB shop manual, you can put the seal on with the cover removed or installed, but doing it installed required two special tools that I didn't have. I also figured it would be easier to get the seal in perfectly square if I had the cover on my bench. Your mileage may vary.

OliverVB · #4 03-31-2009, 08:54 PM

When working with the special sealant, time is of the essence as the sealant sets rapidly. So, be certain that you are actually ready to install the cover before adding the sealant. You must also be careful not to deform the funny little gasket as you install the top chain cover. It is easy to do so and you will end up with a substantial leak. A dry run or two w/o sealant is a good idea. My top gasket leaked almost from new on my '90 300E 2.6 and was re-sealed by the dealer at the 30K mile service. The dealer at that time used red silicone sealant. A BIG mistake. The gasket started leaking again in less that 10K miles. It has been more than a year now since the last re-seal and the area is dry as a bone. When I did mine a little over 1 year ago, the tube of sealant was $12.50, retail, from my dealer. If bought in a full size tube (like household caulk) from a commercial/marine supplier, the price was around $25, at that time.

It is also possible for the valve cover gasket to leak along the sides. At one point, mine did so along the plug (right) side of the engine. During a routine safety/etc. inspection at the dealer, a trained Benz mech. told me I had a head gasket leak. A new valve cover gasket plus a good cleaning and the "head gasket" leak was cured! Like others, I don't like to use sealant on this gasket as it makes replacement troublesome. Have been there before on older cars where that gasket was glued on at the factory. On the M103 engine the job is pretty easy and quick so no big deal if it leaks again. Besides, it gives us a reason to poke around in the engine bay again.

I would definitely go with the Mercedes gaskets for these critical areas as you can then be certain that you have the better quality and the latest versions.

tinypanzer · #5 03-31-2009, 11:07 PM

Yes, Oliver you are correct. The sealant does set up fast.

In the MB manual it says "apply sealant......" "Attach parts within minutes"..... (Or something to that effect). "Within minutes" is verbatim, however.

quesnoy · #6 01-04-2015, 06:22 AM

Great write-up. I've also just finished completing the job of replacing the upper timing cover gasket and and cam seal. I actually used the write-up on peachparts.com as a guide. The only thing I found difficult was installing the cam seal once the cam cover is on the car. When trying to squeeze the seal onto the cam shaft, the little retaining spring in the seal kept popping out. Then I wised up and placed the seal onto a socket that was the same diameter as the cam shaft. That sealed the spring in place and allowed me to simply slide the seal onto the cam.

Here is a video of what I'm talking about:

http://youtu.be/6xQCWZj0MIo