Author Topic: excessive valve tappet noise  (Read 7920 times)

johnk

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excessive valve tappet noise
« on: August 05, 2014, 12:56:44 »
Gentlemen
My 1968 280sl seems to have excessive tappet noise despite a recent valve job. It was noticeable to me before the valve job as well. I just purchased it in April of this year. We replaced the valve guides, ball studs and rocker arms, but did not replace the springs and the lash caps/washers. Buds sent me the wrong valve springs and I did not want to have to wait any longer. I passed on the thrush washers as the only ones I could find were almost $500 for the set.
I have readjusted the valves a few times, and while it sounds better it is still very noticeable. Any ideas what the issue could be? I can install new springs and lash caps if that could be the problem.  The car has 74,000 miles on it.

Thanks
John K
John Krystowski
Avon Ohio
1968 Euro 280sl under restoration
2016 Jag F-Type R sold june 2021
1950 Alfa Romeo 6C 2500 SS For sale
2008 E350
2007 GL 450
2019 BMW 540

ja17

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Re: excessive valve tappet noise
« Reply #1 on: August 05, 2014, 13:31:01 »
Hello John,

There are several unusual problems which can cause "tappet-like" noises that are not related to valve adjustment. First of all check to make sure that the valve cover hold-down straps have not distorted inwards. You must have approx. a minimum of 1/4" between the three straps and the camshaft. If not when the valve cover is tightened down, the straps pull in-ward and against the camshaft causing a "tapping noise" as the camshaft rubs against them. Simply bend the straps out and away from the camshaft to cure the problem.

Another item to watch out for after head work............The rocker arms "arch" over the top spring retainers to reach  the  contact pads (lash caps). After head work the rocker arm  geometry may change enough to cause the
rocker arm to contact the upper spring retainer rim where it crosses onto the contact pad. In this case when the camshaft contacts the rocker arm, the rocker arm contacts the upper spring retainer rim BEFORE it presses on the contact pad. You get a "double hit" which also creates a tappet noise. Inspect each rocker arm where it arches over the upper spring retainer. Remove the ones which look close and inspect the arch on the bottom of the rocker, you will see a noticeable "wear mark" if this is happening. To fix, grind the arch a little higher so it clears the rim. Re-adjust the valves on any that you work on.

Keep us up to date. Let us know if you need more information on these fixes.
« Last Edit: August 05, 2014, 13:41:00 by ja17 »
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

johnk

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Re: excessive valve tappet noise
« Reply #2 on: August 05, 2014, 17:40:17 »
Thanks Joe,

I will give the rocker arm issue a look and see if that could be the problem. The valve cover brackets did clear the camshaft, but I will recheck to make sure the clearance is at least 1/4 inch.

John
John Krystowski
Avon Ohio
1968 Euro 280sl under restoration
2016 Jag F-Type R sold june 2021
1950 Alfa Romeo 6C 2500 SS For sale
2008 E350
2007 GL 450
2019 BMW 540

garymand

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Re: excessive valve tappet noise
« Reply #3 on: August 05, 2014, 19:53:54 »
A few other points to consider:

1) The clearance is very tight, tighter than what I was used to on American solid lifters: 0.004 and 0.008
2) I like them tight.  It is a stug pull on the feeler gauges.
3) I don't like to adjust hot because it takes me a while and the motor cools off.  I prefer to do it cold.  
4) I always go around twice.  Once to adjust and once to verify.  Sometimes I find one too tight or too loose.
5) Always look for wear on the lobes AND on the back of the cam lobes.  I ran across a picture someone here submitted and you could clearly see that more than one cam lobe had seen constant contact all the way around the lobe.  That means the valve never closed fully, and the gap was 0.00000, zero, zilch, nadda.
I'd rather hear them a little than not at all! (Its better to be too loose than too tight!)
6) It is tricky too, because with age and infrequent adjustment, the balls wear into the lifter sockets with a ridge an valley.  When you rotate the ball, that orientation changes and will have a tendency to wear rapidly resulting in a loose gap sooner than more round shapes.  I've seen little posts left at the tops of the balls as the balls wore down around the hole in the lifter, but still, they held clearance pretty well because the car wasn't drive much.

http://www.authenticclassics.com/Valve-Cover-Label-Decal-for-Mercedes-280SL-p/auth-003776.htm
http://www.sl113.org/wiki/Restricted/ValveAdjustmentTour

The 'tour' is not out of the manual, but a good tutorial of 'how' you do it.  notice the head should be retorqued hot and with the motor hot you can adjust the valves hot to 6 and 10 rather than 4 and 8. 
« Last Edit: August 07, 2014, 21:07:25 by garymand »
Gary
Early 250SL German version owned since 71, C320, R350, 89 Porsche 944 Turbo S

johnk

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Re: excessive valve tappet noise
« Reply #4 on: August 06, 2014, 04:01:25 »
thanks Gary. I am hoping that its just that my definition of snug was a little too loose. I should find out in a day or so as an experienced friend of mine will be rechecking them. We will be checking the items Joe suggested as well.

John
John Krystowski
Avon Ohio
1968 Euro 280sl under restoration
2016 Jag F-Type R sold june 2021
1950 Alfa Romeo 6C 2500 SS For sale
2008 E350
2007 GL 450
2019 BMW 540

wwheeler

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Re: excessive valve tappet noise
« Reply #5 on: August 07, 2014, 19:39:28 »
3) I don't like to adjust hot because it takes me a while and the motor cools off.  I prefer to do it cold. 

Please correct me if I am wrong, but I believe the specs are when the engine is COLD. The BBB seems to be definite about that and that is the way I have always done it. 
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

garymand

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Re: excessive valve tappet noise
« Reply #6 on: August 07, 2014, 21:08:15 »
Please be corrected. ;D
Gary
Early 250SL German version owned since 71, C320, R350, 89 Porsche 944 Turbo S

Cees Klumper

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Re: excessive valve tappet noise
« Reply #7 on: August 07, 2014, 22:20:05 »
Yes, valve clearances are set on the engine cold.
Cees Klumper
1969 Mercedes 280 SL automatic
1968 Ford Mustang 302 V8
1961 Alfa Romeo Giulietta Sprint Coupe 1600
1962 FIAT 1500S OSCA convertible
1972 Lancia Fulvia Coupe 1.3
1983 Porsche 944 2.5
1990 Ford Bronco II

garymand

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Re: excessive valve tappet noise
« Reply #8 on: August 07, 2014, 22:56:47 »
Hmm, where is it in the BBB?   I'll take a look tonight.  I don't remember hot numbers in the BBB actually.
 
 Why is it on this: http://www.authenticclassics.com/Valve-Cover-Label-Decal-for-Mercedes-280SL-p/auth-003776.htm

I've never seen this as an original decal on a valve cover, so I have never seen one in person, but why would they reproduce a false or incorrect decal?  Aside from the motor cooling off, due to the head retorqueing and then valves adjusted, I thought it resonable to have a hot setting because my 58 Chevy required setting the solid lifters with the motor running.  That was great fun.  I still rem,ember they were 8 and 10 hot.
Gary
Early 250SL German version owned since 71, C320, R350, 89 Porsche 944 Turbo S

Garry

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Re: excessive valve tappet noise
« Reply #9 on: August 07, 2014, 23:36:33 »
I actually have a few of the original ones of that decal. I understood that it applied to the 280SL only?

Someone else here who is an expert on labels can chime in anytime.
Garry Marks
Melbourne/ Kyneton, Brisbane. Australia
1969 MB 280SL 5 speed RHD SOLD.
1965 MB 230SL Auto RHD Lt Blue 334G, Top 350H, Tourist Delivery.
1972 MB 280CE Auto RHD 906G
2005 MB A200
2006 MB B200
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66andBlue

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Re: excessive valve tappet noise
« Reply #10 on: August 08, 2014, 00:23:07 »
Hmm, where is it in the BBB?  .....  
Page 00_3/1
Why would anyone put absolute faith in a reprinted label??
Alfred
1964 230SL manual 4-speed 568H signal red
1966 230SL automatic 334G light blue (sold)
1968 280SL automatic (now 904G midnight blue)