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1989 300te...I was at the mechanic's today...as a result of loud tapping sound, the valve cover was removed, to reveal a worn lobe at cylinder #1. What to do now? I could drive it "into the ground", but I know that eventually it will start 'missing' and causing me grief. I could get rid of the car, but I have put $$$ into it (new hydraulic suspension parts, new shocks, some bushings here and there... money).
Mechanic says "Look for a clean used cam with the rockers- must have mated rockers or I will need new ones".
Where do I get such an item...one that I can trust and won't blow out in 6 months?
Any thoughts on the matter?
 

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Ah, you've discovered the soft camshaft problem found on a lot of the "early" M103 engines. Lots of camshafts and rocker arms were replaced under warranty. Dealers were supposed to paint a white dot on the top of the rocker cover (at the back) after perforning a camshaft replacement.
Early M103s (the first few years, actually) had tin-plated camshafts. The tin was supposed to allow cam/rocker arm break-in but that didn't work out so well in a lot of cases. The revised design included a chilled iron cam and rocker arms with brazed-on carbide pads. Neat.
When I installed the 3.0L drivetrain in my 88 260E I found that the 3.0 camshaft had some worn lobes and nasty rocker arms. The new cam cost about $300 and the rocker arms were something like $40 EACH. Times 12 that was an unpleasant surprise, but whatcha gonna do?
You could cruise salvage yards and look for a damaged 3.0 with the later rocker arms. That's a sure sign that the upgrade was done. 2.6 cams are different.
 

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At the moment I have only a tattered copy of an Alldata printout. It references MBNA SI 05/3b, 18/7b from May of 92. This SI replaces SI 05/3a, 18/7a from April of 1989. "Engines 102 and 103 inspect the camshaft and rocker arm contact surfaces for wear."
The bulletin then goes on to give specifics about engine 102 and the chilled iron cam/carbide rocker arms but not the 103. I know I have the info somewhere and even saw the engine s/n breakpoint for factory-installed chilled iron camshafts. Time to dig.
 

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If you're worried about cost, and you don't mind doing the work, changing the cam is something you can do yourself. I had the same problem on my '88 300E several years ago and decided to tackle it myself to save money. And I am not experienced; just learning as I go and following the shop manual.

Although the cam itself is right on top and easy to access, you do have to pull the fan, distributor, etc. to remove the timing chain. As long as you have access to the shop manual, a decent set of tools, and a day of patience, you can do this and save a bundle.
 

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i'm a fan of DIY but chaning a cam is something i'd never do myself. You do need some knowhow and a decent torque wrench, plus it happens sometimes that you have to redo the engine timing or find something wrong in the process...
 

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There is another update that needs to be done to the early M103 heads that eliminates one of the causes of flat lobes. I find it interesting that the first post in this thread talks about a failed number one cylinder lobe. The problem with the early M103 is that the oil sprayer bar is not secured at the center and this allows it to move upward under pressure - starving the sprayer bar for oil - which affects the number one and six cylinders more than any of the others. There is a simple "U"shaped retainer that should be installed under the bolt that secures the center cam bearing support.
 

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another cause of cam failiure is using engine flush on an old engine that has deposits in it, if a larger bit of crud brakes off, it can get stuck in the spraybar! never use flush on a worn engine.
 

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I have a 1986 300E with 137K miles and I am hearing tapping noise around the distrbutor. I thought it was the distributor and replaced the rotor, cap and back insulator two times! It is still tapping. I am afraid it migth be the cam lobes on #1 cylinder. Is there a way to check without removing the valve covers? How about a compression test? Right now the car is running fine but it idling a little low on intersections, not stalling but sounds like it is about to stall.
 

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You can try using something like a long socket extension bar held to your ear while you move the other end down the valve cover and see if the sound is louder in one area. However, even if you can tell which cylinder is the problem, it could still be a collapsed compensator (lifter) or worn cam.

The best thing to do is to remove the valve cover, which is really pretty easy. Unless the gasket is fairly new, you should replace it at the same time -- less than $15 online. Just remove the eight 10mm bolts and two hoses on the right side, and disconnect the spark plug wires from both ends (leave them in the covered channel on the valve cover). If it's stuck, tap around the edges with a rubber mallet patiently and it will break free. Don't use a hammer because the metal is very soft.

If you can't see the lobes, bump the starter a little to rotate the cam. If the lobes are worn enough to make noise, there will be a significant difference in appearance compared to the adjacent lobes. If this is the problem, you are looking at a new cam and all new rocker arms (a must).

If they look okay, it's probably a lifter. Each lifter should be firm and should not compress when you push the end of the rocker arm towards the spring. If you find one that moves up and down slightly compared to the others, that's your problem, and it's good news. If you get to this point and want info on lifter replacement, let me know.

When you reinstall the valve cover, make sure the u-shape piece in the rear is seated properly, and tighten the bolts gradually to 9nm. Good luck!
 

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No, there is not a way to tell without removing the rocker cover. A compression test won't tell you squat.
Don't be too eager to blame the cam. If you hear the noise way up front it could be timing chain slap.
 

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I agree with the Aug-meister. The cam cover is easy to remove; you just need a new gasket to really seal it up correctly on re-installation. A visual check of the cam and lobes will reveal whether or not you have a cam problem. If you remove it, check to see if the flat metal clamp is installed that I mentioned in a previous post. It is right on top of one of the center cam bearing/rocker supports. If its there it will be overlapping the pressed metal oil sprayer bar. If its not there, any repair you do should include installing one of these cheap little clamps.
 

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Thanks guys....I'll get a new valve cover gasket and will open it up this week end.....augapfel you said something about a "timing chain slap" how do you check for that? The ticking usually starts after the car starts up. Nice and quiet when it is cold.
 

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G'Day mate. I need ti investigate the tapping noise this weekend on my m103. I have what sounds like a tappet but it doesn't go away once oil pressure is up but eventually quietens down significantly (not completely) whenthe engine warms up after about 10 minutes or so. I think it may be a liter so keen to find out what is involved in replacing these suckers and if a bone head DIYer like me can do it.



You can try using something like a long socket extension bar held to your ear while you move the other end down the valve cover and see if the sound is louder in one area. However, even if you can tell which cylinder is the problem, it could still be a collapsed compensator (lifter) or worn cam.

The best thing to do is to remove the valve cover, which is really pretty easy. Unless the gasket is fairly new, you should replace it at the same time -- less than $15 online. Just remove the eight 10mm bolts and two hoses on the right side, and disconnect the spark plug wires from both ends (leave them in the covered channel on the valve cover). If it's stuck, tap around the edges with a rubber mallet patiently and it will break free. Don't use a hammer because the metal is very soft.

If you can't see the lobes, bump the starter a little to rotate the cam. If the lobes are worn enough to make noise, there will be a significant difference in appearance compared to the adjacent lobes. If this is the problem, you are looking at a new cam and all new rocker arms (a must).

If they look okay, it's probably a lifter. Each lifter should be firm and should not compress when you push the end of the rocker arm towards the spring. If you find one that moves up and down slightly compared to the others, that's your problem, and it's good news. If you get to this point and want info on lifter replacement, let me know.

When you reinstall the valve cover, make sure the u-shape piece in the rear is seated properly, and tighten the bolts gradually to 9nm. Good luck!
 
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