timing chain

[piddler]

I have a noise that sounds like the fan rubbing the shroud when I rev the engine. I can find no rub marks on the fan or shroud and the motor mounts seem solid. Someone told me that it might be the timing chain.
Does this sound plausible and how hard (expensive) would the fix be?

This is on a 230sl.

Thanks for any help, Pete

[graphic66]

Could be your valve cover bolts are too tight and the cam is hitting it. Simple check anyways, loosen them up and see if it helps, you may need to pull the valve cover and bend the pieces if they were really tight.

[TheEngineer]

Could be the timing chain slapping against the chain guides. It is tensioned by the tensioner, but that only works if the chain isn't stretched too much. Take the valve cover off and inspect things. Jack up the rear end with a spirit level on the valve cover, until it is level. That way, oil won't run out the back. Use a torque wrench to torque the valve cover bolts properly. It's easy to overtighten them.

[piddler]

Thanks for the advice. I will check this out Monday.

What is the torque value on the valve cover and is the timing chain adjustment accessible under the valve cover?

As yet, I don't have any repair manuals or technical information. Hopefully I will have some information next week.

Thanks again and in advance for any help, Pete

[piddler]

Is the adjustment for the timing chain accessible when the valve cover is removed? What are the torque values for the valve cover? I don't have any good repair manuals or tech specs yet. Hope to have some next week

Thanks again, Pete

[Cees Klumper]

The timing chain is not adjustable, just needs to be replaced if it's stretched too much; this can be done by taking the valve cover off - check this site with the search function, or the technical articles on the homepage (www.SL113.org) since this procedure has been discussed before. For example, here is a short post that is in the technical articles on this topic:

"Dan Caron: timing chain replacement is easier than it sounds. Put the engine to TDC number 1 piston. Remove the chain tensioner, you will need to take the thermostat housing off first. If there's a master link on the chain look for that first if not grind off two pins on the same link. Put a rag around the chain case opening because you WILL drop something in there if you don't. Using the new master link attach the old and new chains together. Slowly feed the new chain in until it comes out the other end and then undo the master link and throw the old chain away. I usually wire the chain to the camshaft while I'm taking the master on or off. The chain can slip off and fall way down it there. Replace the master and turn the engine over by hand a few times to make sure you have it in time. Replace the chain tensioner. I usually put a new one in if the chain is really worn. Bleed the tensioner and put everything back together. You may have to re-time the ignition."

The torque value of the camshaft cover bolts should be 5 NM according to the factory service manual.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[piddler]

OK!! I have the valve cover off. How much is too much slack in the timing chain?

Hopefully, I will have some technical information this week and maybe I can stop asking such basic questions.

Thanks again and advance for all help, Pete

[glennard]

Whoa, Going a little fast here!  The sound of a fan rubbing on a housing and timing chain noise are totally different.  Talk of replacing the chain, etc. seem a little premature.  If something is rubbing and making that much noise there should be evidence of it.  Get the rubber hose ear piece out, etc.  No noise at idle?  Only on reving? :?:

[ja17]

Hello Piddler,
Air rushing through fan itself will make the noise travel and be hard to find.  Try cutting a length of hose to use as a "sound" stethescope and search around.  Anything that turns on the front of the engine can be suspect. Some times an alternator bearing can go bad. For a timing chain problem use a solid wood dowel to make a "vibration" stethescope. Placing it on the valve cover may allow sound vibrations from a faulty chain or tensioner to be detected. Place it on the valve cover and then agaist your ear carefully.

On rare occassions the chain tensioner may jamb allowing the chain to run slack. This may happen after long storage or inactivity. I would definately remove the valve cover and check the chain if you cannot isolate the noise elsewhere. Good advice on checking the camshft for any rubbing etc.

The chain tensioner is hydraulic with spring assist. It automatically hydraulically adjusts by engine oil. Very dirty oil may cause problems. If you find that it is jambed, it can be removed and cleaned. Be careful not to loose the tiny steel ball. Often times just loosening its mounting bolts will cause it to unjamb.  Look elsewhere first this is a rare circustance. If your chain is strectched the noise will come on gradually over time not all at once. Any timing chain malfunction is serious and should be taken care of.

Joe Alexander
Blacklick, Ohio

[piddler]

OK guys, get ready to hold your sides and fall down laughing.

I removed the valve cover and checked the chain. I don't have the specs for this car but the tension looked ok.

While I had the valve cover off I was looking around the front of the engine. I saw that the alternator belt had way too much slack. I had two thoughts: I hope this ain't the problem and I hope this is the problem. Sure enough, I tightened the belt put everything back together and the noise was gone.

I have worked in the maintenance field (not automotive) for 30+ years as a worker, foreman & manager. I have always told my people to look for the most obvious and easiest first and work from there.

I broke my own rule and it cost me a lot of time and probably a lot of snickers from others.  Worst part is that my wife told me at the beginning that it sounded like a loose belt.

The positive side of this is that I did get a lot of good advice and some hands on experience that will probably be helpful later

Thanks again guys, Pete

PS this will probably not be my last or worst mistake

[glennard]

All's Well, That Ends Well.