My car is an 87 300e with 159k miles. I developed a clicking noise originating from somewhere around the valves. Pulled the valve cover and discovered that one of the camshaft lobes was terrribly worn, and the others were on there way to a similar fate. The one lobe is so flattened that it comes to a point on one side. I have quite a few questions concerning my situation:

1. first, what could have caused this? I do have a oil leak, but I have always been quite meticulous with checking and refilling. I was under the impression that these have fairly hearty camshafts, so what could have done this? My girlfriend's dad, who is helping me with this project, has a theory. He noticed that each of the "bridges" (for lack of a better term) that hold the rocker arms is marked with a pin hole. 1 hole for the first bridge on the engine, two for the second, and so on. He thinks that a previous owner replaced only the camshaft, but not the rocker arms, hence the need to mark them. This makes some sense to me considering the cost of the rocker arms, and the fact that a new camshaft alone would make the car run pretty well for the time being, so he could onload it. Would there be any other reason to remove and mark the rocker arm bridges, other than replacing the camshaft?

2. What exactly is involved in replacing the camshaft and rocker arms? my girlfriend's dad seems to think it is fairly straightforward. Is it just remove rocker arms, remove camshaft, replace and your good to go? or is there a lot more to it? He also described some sort of method of tieing the timing chain so as not to have to adjust timing at all when the new camshaft is put in. Anyone done this with the timing chain on an M103?

3. Is there anything else I should replace or worry about being damaged as a result of this camshaft failure? Anything else that should be done while I have this part of the engine apart? (although I am reluctant to do anything else that will be very costly, as I am already low on funds from camshaft/rocker arm purchase). I already plan to change out oil and filter after project.

4. My oil leak is most likely the upper or lower timing chain cover, is there any reason why resealing this would be easier while the camshaft is out (doubt it), or should I do this as a separate project at a later date?

Thank you for your time, all replies are greatly appreciated,

Jay

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headrivenoise... listen.

I found a camshaft at a junkyard for $145. Is it foolish to buy and install a used cam? (Waiting for reply on condition). I also found an entire "good running" engine with 80k miles for $650. Does that sound fishy to anyone else?

All replies are greatly appreciated.

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headrivenoise... listen.

Points to consider:

- the tensioner has to come out. It's a ratcheting tensioner that must be reset before installation.

- the distributor has to come off to replace the cam so have a horseshoe gasket ready and read up on the sealant recommendations for this critical sealing point. There is a different sealant spec for the corner where the head meets the block and the gasket contact surfaces. I used Toyota brand semi-drying sealant (for oil pans) in both locations and had no leaks.

- there was an oil feed line redesign. The manual says to use the later design. I don't know part numbers but I believe this was settled in the early days of the M103 so a 300SE/L (88-91) should have the new design.

- early hardened camshafts should be installed with matching hardened rockers, later chilled cast camshafts should be installed with matching carbide metal coated rockers. The break point is early 1989. I don't know how to tell one type of camshaft from the other.

- how new/old are the valve stem seals?

$650 for an M103 is not a bad price but is it better than what you have? It probably needs head work. Since the bottom end is pretty tough, you might be better served by getting head work done to your engine.

Sixto
95 S420
87 300SDL

The used cam can be installed if it meets the following criteria:

1. The cam is healthy with no scuffing.
2. The cam and matching followers are all replaced.
3. The cam and followers are all in their exact respective locations in your engine, they cannot be jumbled during the transfer.

Beyond that, I'd worry about what caused the initial failure. What was the failure pattern?... all intake lobes?... all near one end of the engine?... random?

I'm not exactly familiar with the M103. How are the lobes lubricated? I'd look for oil starvation in the form of plugged oil passages and try to remedy that.

One tip on installing the cam. Mark everything and make sure eveything is in sync. I like to turn the crank to 0° then mark the cam sprocket at some logical place so the replacement cam will go in the same way.

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95 E320 Cabriolet, 159K

Sixto: I was able to get the camshaft out without removing the tensioner, do I have to remove it for some reason?

I'm getting the recommended loctite sealant, but after much reading on the forum I am still not totally clear on all the spots to put the sealant. Would you mind giving me a synopsis of all the spots where it is needed to properly seal, and if you applied it thick or thin in each spot? Also a description of how you placed the cover back on the engine to successfully create the seal. I am also replacing the circular gasket that is inserted in the cover and surrounds the camshaft, do you know if this takes sealant as well? Thanks in advance.

Kestas: All the lobes on the intake side were severely worn, while the exhaust side was perfect. This makes me suspect oil starvation, because the engine is tilted away from intake. Is there anything else that could cause intake only lobe wear? Thanks in advance.

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headrivenoise... listen.

I might have worded the previous post poorly -

One kind of sealant goes in corner where the head meets the block. Just in the corner. Then slide the horseshoe gasket into place. Apply the other sealant to the vertical surfaces of the front cover/distributor housing that contact the head. Lubricate the top of the horseshoe gasket with spit so it doesn't move when you put the front cover in place.

The front camshaft seal doesn't need any sealant. Oil the rubber lip before you slide it over the camshaft.

Sixto
95 S420
87 300SDL

Just what I needed. Thanks Sixto.

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headrivenoise... listen.

Unless you strongly suspect it was a case of running low on oil at some point, I would try to find the oil circuit diagram for your engine and look for logical places where oil can get blocked for the intake cam, to avoid wiping out another cam.

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95 E320 Cabriolet, 159K

No need to remove the tensioner if you can get the sprocket on the new cam.

Make sure the 3 bolts that hold the sprocket to the cam fit the replacement cam. Older cams have M6 instead of M7 bolts holes. Check also that the bolts fit through the holes in the sprocket.

Sixto
95 S420
87 300SDL

After reading this post I'm starting to worry about my 86 300E that's just coming up on 137K miles.

Sixto, you stated the following:

"- there was an oil feed line redesign. The manual says to use the later design. I don't know part numbers but I believe this was settled in the early days of the M103 so a 300SE/L (88-91) should have the new design."

Is this an inherent problem on early M103 engines as regards the oil feed line? Would it be prudent to update the oil feed line to the later spec? Where is the oil feed line anyway?? Any idea on cost if I do it myself?

Thanks for any advice.

Gary

Sorry, sixto, but I have one more question. One sealant I am using is a dirko sealer part # 001 989 61 20 10, and the other is a curil sealer part # 001 989 25 20. I am pretty sure the dirko is the sealer that goes in between the vertical surfaces where the head and the timing chain cover meet, and the curil is dabbed where the head meets the block. Am I correct?

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headrivenoise... listen.

disregard the dirko part #. It's not working for some reason. Thanks.

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headrivenoise... listen.

whoops! Disregard the whole question sixto. I remembered that an article steve brotherton wrote about resealing the same thing on the 104 engine mentioned part # for the sealants. Turns out I had them backwards. The dirko is for the head/block/timing cover point. Thanks again for all the help. The whole mess should be done wednesday so I'll post the results.

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headrivenoise... listen.

Gary,

The replacing the oil feed line is easy. It sits atop the cam towers and is held by 3 bolts. I'm not sure if there are plastic fittings to replace as well.

Sixto
95 S420
87 300SDL

Phalcon51,

Could you post a pix once you've found it, as well as details on procedure and parts. I'd appreciate it...

cheers,

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sjsfiji

'87 W124 260E (DD)
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'97 993 Carrera
106K orig. mi.
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