[W126 Coupe] Valve tap/ticking

[gerryvz]

Hi Ken,

This is likely due to one of several causes: a scored/flattened camshaft lobe, scored/dished rocker arm, or a non-operating hydraulic compensator element ("lifter").  It's not a surprise that it is happening on the right (passenger) side of the motor -- it's very common at 150K+ mileage to have valvetrain issues on the passenger side due to lubrication-related issues. My own motor developed a ticking noise last December on the passenger side on the front-most cam lobe/rocker arm, which caused me to undergo a heads-off top-end rebuild (which I documented and discussed here).

What you need to do is to remove the cam cover (just a few bolts) from that side, get a good flashlight or shop light, and carefully examine each of the cam lobes and rocker arms for visible scoring on the surfaces that touch.  It's highly likely that you have a scored cam lobe/rocker arm due to a lubrication issue -- at some point, not enough oil got to the friction surface and this caused metal-on-metal contact, which only after a few miles begins to flatten & score the cam lobe and dish out the rocker arm where the lobe hits it.

Only a good visual examination will tell you exactly WHERE this situation exists. But it's more important to attack the CAUSE of the problem, which as I said is generally lubrication-related. Often this has to do with the cam oiler tubes that supply oil both to the cam bearings (the rotating surfaces of the cam in the cam towers) and to the cam lobes themselves.  The oiler tubes have small brown plastic fittings that supply a constant stream of oil down into the rotating cam bearings (the fittings press into the tops of the cam towers), and these brown fittings often crack and then don't supply the necessary oil to the cam bearing surface. These are very cheap parts -- I believe they are about $6-8 a set (two sets needed) from MB. It's amazing how such a cheap part can very quickly destroy an expensive cam and/or cam towers.

Also, the little holes in the oiler tubes that drip oil directly down onto the cam lobes themselves can get clogged over time, starving the cam lobes and rocker arms of their precious supply of oil. This is likely what happened in your situation -- there is not enough oil getting to your cam lobe from the oiler tube.

If you are so inclined, the fix for all of this can fairly easily be done as a DIY job -- or as a fairly inexpensive shop job by an indy mechanic. If indeed the cam lobe(s) are flattened and the rocker arm is dished, then you will most likely need to get a replacement cam. They are available used for cheap, or you can get a new aftermarket cam for around $500. I think the MB price for a replacement US 560 cam is between $700 and $800. If you replace the cam, you really should also replace all rocker arms on that side of the motor as well - there are 16 rocker arms and they run around $20-30 apiece.  The rocker arms require a special tool to press down on the valve springs, to slide each rocker arm out. The cam requires removal of the cam sprocket and loosening of the timing chain tensioner and timing chain on that side. It's probably also a good thing to replace the timing chain guide rails -- there is a small plastic chain rail and a larger banana-shaped tensioner rail. The rails are cheap ($8 for the smaller one, and ~$50 for the banana tensioner rail) but the tensioner itself is a bit spendy. Don't scrimp on the tensioner -- get the original MB part (not aftermarket) and you will need to pay upwards of $150 for that MB part.

It's also a good opportunity to get a new pair of cam cover rubber gaskets Be sure to get a good supply of the small copper crush washers that you use with the bolts that hold the cam covers to the heads. These washers shouldn't be reused, and the cam cover bolts are really only snugged down, NOT tightened or you will warp the metal cam covers. I think the spec is around 6-8 ft-pounds for the cam cover bolts.

As I mentioned, you need to get a valve spring compressor tool, and an inexpensive tool to pull the press-in pins that hold the timing chain rails to the head. I would be happy to loan you my tools if you are inclined to do this job yourself.

One other tip, looking forward. The oil you use with your car is now critical. Oil companies have changed the formulations of their oils, and they contain much less ZDDP (zinc) than oils have in the past. Having ZDDP in the motor oil (dino oil, not synthetic) is IMPERATIVE for successful long-term lubrication of the friction/wear surfaces of our older motors. Only a few common, commercially available dino motor oils have enough ZDDP in the appropriate quantities. Two of these oils are Chevron DELO 400 and Shell Rotella-T. I have been using Chevron Supreme motor oil in my 560SEC for the past 8 years, and am now changing over to DELO 400 for the first time with the coming oil change I'll be doing a month or so from now.  This is more important than ever to use the correct oil that meets the lubrication needs of our cars. Other good oils with appropriate ZDDP levels (but less commonly available) are Schaeffer and Red Line brands.

Good luck, and keep us informed on what you are doing.

Chet Hwilka's write-up here (http://home.comcast.net/~chwilka/cylinder_head_removal_and_replac.htm) on removing the cam/rocker arms was INVALUABLE to me (I hope to meet him & vigorously shake his hand someday), and you are welcome to see my own illustrated write-ups from my own top-end job at: http://www.facebook.com/album.php?aid=167571&id=821723571&l=946f984ee3 and even better with commentary here on my web forum: http://www.500espot.com/forums/viewtopic.php?f=46&t=626

Cheers,
Gerry




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> I have an 86 560 SEC with 330,000 miles on it.? The top end was done at around 250,000, and ran pretty good up untill recently.? I have developped a tapping/ticking noise on the right hand (passenger side) valve bank.? It seems to be coming from one of the middle lifters/rockers.? I initially thought it might be a st icking hydraulic lifter, so I added seafoam, to the oil, and ran it for about 100 miles, and changed the oil.?That didn't seem to make the problem worse, or better.? ?The noise is worse when the motor is hot, and it is pretty bad.? I am trying to nurse the car along for a little while longer, till I can retire it as an everyday driver.? I have my sights on getting a 2003-2005 CL55.? Anyway, if anyone can shed some light as to the possible problem, and cure, that would be appreciated.

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> Thanks

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> Ken

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> Kenneth N. Hartz, President

> Advanced Mortgage Services, Inc.

> 946 Farnsworth Ave.

> Bordentown, NJ 08505

> (p) 609-351-6565

> (f) 609-479-3557

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