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  #1  
Old 08-22-2003, 01:50 PM
moraine
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W123: Noise after replacing valve nuts

1985 300CD-T.

Prior to acquring the vehicle, someone adjusting the valves used too much force on the adjusting nut at each valve. This resulted in the nut sides being damaged and made it very difficult to fit a wrench around the nuts.

Recently, I replaced all 10 of the cap nuts and adjusting nuts and set the valves to factory manual specs. The result has been that when first starting the engine after letting it sit for 14 hrs. or so, there is a noticeable clacking for around 5-7 seconds that then goes away. I have since rechecked the valve clearances and they are all within spec. Does anyone know if the addition of new cap nuts would cause this abnormal clacking for a while? It just seems that the valves are noisier than they used to be

I'd appreciate any advice on this. Thanks
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  #2  
Old 08-22-2003, 02:39 PM
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There are two differant style of nut . One style were for the pre hardened cam, (pre"80', I think) Dont know if this has anything to do with your problem but you might check and make sure you got the up dated nuts, no joke intended. The manual says " The cap nut w/o the crome plating must not be used with the hard backed rocker arm" (yours) If you still have the old ones see that the taper BETWEEN the part where you put your wrench on and the Top servace are the same.
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Old 08-24-2003, 03:24 PM
moraine
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Thanks for the info., Stevo. I'm doing some checking on the possibility that there could be two different cap nut types - so far, I haven't seen anything though.

Appreciate the help
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Old 08-24-2003, 10:25 PM
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Ya, like I said I have no idea what would happen if you had the older caps. Were your valves WAY tight before you adjusted them, cause they will be noisier when you bring them back to spec.

Steve
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Old 08-25-2003, 08:27 AM
moraine
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I recall that three, maybe four, were overly tight - those where getting the wrench on was most difficult. Thanks for the help
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  #6  
Old 08-25-2003, 09:17 AM
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moraine,

It may not be the acorn nuts you replaced at all. If the noise goes away after a few seconds I would not suspect a purely mechanical cause. You may have made the noise that normally occurs different by adjusting the valves correctly, but there are relatively few cases of mechanical things changing position or shape by themselves in a few seconds.

The chain tensioner is energized by oil pressure and until you have oil pressure throughout the engine you get some nasty clanking. Oil pressure is intended to come up to the normal value pretty quickly, however there are some features in the oil system that can wear out and make the process take a few more seconds than is usual. The most probably cause for extended operation waiting for the oil pressure to come up is having the oil filter housing drain into the sump when the car is not running. The filter housing design is intended to preclude this by sealing the drain passage to the sump at the bottom of the housing with the stem or rod of the oil filter housing cover. The seal is accomplished by two small O-rings at the tip of the free end.

When you change oil, you should replace the two small O-rings at the free end of the center rod attached to the oil filter housing cover. These two O-rings often do not get replaced for decades and they will harden over time. Eventually they do not seal the oil volume in the housing overnight, and when you first start up you have to pump enough oil to fill the filter housing before you make pressure. During this time the engine gets a little noisy and it is also the time when most of the daily wear occurs.

Hope this helps, Jim
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1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
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Old 08-25-2003, 06:13 PM
moraine
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Thanks for the information, JimSmith. I'm very attentive to the two o-rings on the center rod of the oil filter housing and just did an oil change where I replaced them so I think things are ok there. Watching the oil pressure needle, it seems to move about the same upon start-up as before I replaced the nuts on the valves. Your description of things was helpful, I appreciate it I'm continuing to look into this-
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  #8  
Old 08-26-2003, 01:03 AM
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That passage way inside the tube those two orings go on needs to be checked for openness also.... it not being fully open will also cause noises to last longer than they should.
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  #9  
Old 08-26-2003, 01:22 AM
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So does anyone know what would happen if one were to install the early caps on the later engine. the rockers would ware them down fast maybe, surely not causes noises tho?

Steve
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  #10  
Old 08-26-2003, 10:23 AM
moraine
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Since I've been doing the oil changes on our M-Bs, as a routine, I have a can of air that I use to shoot air through the little hole in the top of the center rod of the oil filter housing (point the end into a bag or something, a mess results whichever way it is done).
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  #11  
Old 08-26-2003, 02:20 PM
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A very good habit...
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