450 sl engine noise - PeachParts Mercedes-Benz Forum

belowme · #1 05-30-2006, 09:40 AM

Just bought my first mercedes and love it. Drove it home from l.a. and it drove perfect. 16 mile per gallon, temp about 180, lots of power. Now after a trip to SAN Diego, (two hours) it has a slapping sound coming from the passenger side under the valve cover. I dont know much about these motors as I am a former bowtie lover. Any help will be accepted with a smile. The car is stock with 155,000. miles.

Tomguy · #2 05-30-2006, 10:50 AM

What year is the car? 75 was the last year for manual-adjustment ball studs. 76 and up have hydraulic ball studs. It could be a sticking stud, or one that needs adjustment. It could also be an exhaust leak at the manifold. The valve cover is kept on with only 4 10mm bolts and is VERY easy to take off. Remove the air cleaner, pull the wires off the plugs, and then pull plastic wire holder with the wires still in it so you don't even need to look at the cap and firing order to replace them. Take the valve cover off with the exhaust manifolds cool enough to not smoke any oil that might leak out. Worst case scenario, you may have had a blocked oiler tube that caused a cam lobe to become eaten

Tell us what you see. Now, if the problem sounds like chain slap, it could be a broken chain rail... So make sure the rail isnt cracked before firing the engine again!

kbannister · #3 05-30-2006, 12:03 PM

I believe you have this same thread in the Sl forum, and there are several responses there all relating to the same issue that you may have a broken chain guide or broken tensioner resulting in a slap from your timing chain. Continued use of the engine before investigating and repair could have catastrophic results.

Pull the cam cover (rocker cover) on the passenger side and inspect for damage. The cause slapping sound you describe should be evident. If it is a timing chain issue, there are several posts here on how to do the replacement. Not difficult, rather time consuming, but a necessary one if that is your problem.

belowme · #4 05-30-2006, 02:45 PM

Sorry, I Forgot The Year.
It Is A 1978 450 Sl. 155,000. Miles.
Thanks For The Quik Responce. I Took Off The Rocker Cover And There Is No Evidence Of A Timing Chain Problem. It Is Tight And Looks Almost New. I Have No Records Of The Car But I Sure Love It Already. The Sound Matches The Rpm Of The Cam Shaft. I Assume The Lifters Are Hydrolic And Replaceable.????? I Do Restore Vintage Cars As A Side Buisiness And I Am Hopeing To Tackle This Problem. I Just Dont Want To Make The Situation Worse.
Thanks, Roy

t walgamuth · #5 05-30-2006, 08:05 PM

if it has hydraulic lash adjusters sometimes a change of oil type will cure it. what are you running?

tom w

Tomguy · #6 05-30-2006, 09:52 PM

They are easily replaceable and are $30.36 each at FastLane... If you click the "Buy Parts" link up top and enter "A4180-15405" in search you can see. Make sure the large guide rail on the leading edge of the chain is not snapped. It should look like this one:

http://img.eautopartscatalog.com/live/A504015626SWA.JPG

Motorhead · #7 05-31-2006, 03:05 AM

Before you go and replace the ball studs, try a quart of Rislone oil treatment. I have used this treatment with GREAT success on numerous VW's with hydraulic lifters. It worked on aircooled type 4 engines and on the inline 4 cyl jetta engines. I have used it on Chevys also. It is a real fine lubricant and has some solvent characteristics. It is NOT STP or "Motor rebuild in a can".

Please be darned sure that you don't have a chain guide or tensioner problem. A friend of mine lost a good 380se engine because of a broken chain guide. Engine lost valve timing and bent a bunch of valves.
You won't lose much trying the Rislone. Pour it in a warm engine and run it at 1500 to 1800rpm for 5 minutes. See if the noise goes away. Let us know what you find.

belowme · #8 06-01-2006, 02:58 PM

Well Last Night I Grew Some Large Ones Marked Everything And Pulled Apart My Top End. I Found Perhaps Two Problems. One, There Are Two Flat Rockers. The Tops Of Them Are Worn Out. I Assume That The Lifters For Those Are Bad. Also I Broke The Plastic Keepers For The Oil Line. I Plan To Replace All Of The Lifters, And The Rockers. The Cam Still Has A Mirror Finish On All Lobes. Timing Chain Is Perfect As Well As The Tentioner And Plastic Keeper.
If There Are Any Suggestions As To Any Thing Else I Should Do While In There, Please Let Me Know.
Thanks For All The Help, Roy

Tomguy · #9 06-01-2006, 03:52 PM

Are you referring to the studs? This engine does not have lifters - it has overhead cams. The cam shouldn't have a mirror finish on it (although this is almost always common on the lobes themselves), a mirror finish typically indicates wear through the hardened surface - the non-raised parts should at least have this visible. Inspect all of your lobes, none should be flatspotted or have angles at the tips, it should be a smooth curve - not a sharp one. The plastic oiler tube bits are cheap and available in a kit.

Flat rockers almost always mean the lobes on the cam for those are flat too. Closely inspect the lobes that were on those. Flat rockers WILL cause a loud top end.