Valve noise

[Ricardo]

I hope someone has some experience to offer here.
The problem:
On start up my 250sl's engine runs beautifully, smooth and even and very quiet. After warming up for 4-5 minutes, it starts sounding like the valve lash is too loose and gets progressively louder. When driving it almost sounds like there could be contact between the engine and body(I've checked and I have all new mounts); like the valve train sound is being transmitted through the body, not terrible but noticeable, even with the soft top noise. If you stand next to the idling eng. it's not so bad, seems a little loud, but still smooth and even. I've adjusted the lash 3 times since having the head overhauled, each time thinking I got it a little better, but always the noise returns. I've tried listening with a mechanics stethascope (sp?) but I can't pin point a location for the noise, doesn't seem like any one valve is at fault or that there is a source of the clatter. I've started thinking it could be wristpins or the Injector pump or..... A buddy was over yesterday, who has worked on various vehicles while living in the Yukon, and he said "that doesn't sound like wristpins or bearings to me", and we got to wondering if it could be a tired valve spring that shrinks as it warms up or something else in the valve train, that moves as it warms. I'd hate to go looking for a new engine and find out it was something fixable, but I'm sure it shouldn't be this loud and that it wasn't before I had the head overhauled. Anybody?
Richard V

[Cees Klumper]

Hi Richard - because you say "When driving it almost sounds like there could be contact between the engine and body" it may be worthwile to check whether a tube that runs between the firewall and the engine is actually making contact with the firewall. Sorry, I don't know exactly which one, but it may be the tube that provides fuel to the cold start injector that runs from the left to the right side of the engine, tigthly in between the engine and the firewall. This may be a bit of a long shot, but several W113's have had a persistent and very difficult to pinpoint noise from the engine bay, and it turned out to be this pipe.

[Ricardo]

Hey Cees
If it only made the noise when cruising I'd be inclined to agree with your suggestion. Unfortunately if I just start it up and let it idle without moving the car, the clatter will come on after 4-5 min. I'm convinced it's internal, but can't figure out what would change in the valve train as the engine warms. If you just walked up to my warm idling car, you'd say "you should adjust those valves" If you heard it cold you'd say "thats a lovely sounding engine". It starts coming on just perceptably after 4 min.or so, another min. or two and it's quite obvious.
Richard

[ja17]

Hello Recardo,
Looks like you will need to get into the unusual catagory of noises. Two things come to mind. first, sometimes the metal strap which the valve cover bolts to may deflect inward and rub against the camshaft causing a tapping sound. Tightening the valve cover bolts makes the sound worse. Check for this by removing the valve cover and inspecting the clearance between the camshaft and these two steel straps. Next sometimes a rocker arm may wear badly. This can only be checked by removing each rocker arm one at a time and checking for a badly worn contact surface. Good luck!


Joe Alexander
Blacklick, Ohio

[Bill Rader]

Hi Richard
I've had valve train noise since I bought my car over 2 years ago.
I would adjust my valves and it would sound great for about 5 or 10 mins then it would sound like krap again.I would adj them again and the sound would come come back after it got hot.I adj them again but noticed some didn't need adj but the others did. So I adj them again but this time I wrote down the ones that were out of spec.Then I got it hot again then I checked them hot and noticed the stud adjusters on the ones that were changing turned way too easy.I pulled out the rockers and found the tops of some of them were worn and one stud was so loose I could turn it by hand! After I let it cool down it was harder to turn.I replaced the studs and it made a huge difference.
Bill Rader
68 250SL

[Ricardo]

Hi Bill
Now that sounds promising !!!
I know one of my adjusters was a little rounded off, the one you really can't get on with any open end wrench, intake on no. 2 I think, and I had to remove the rocker to get a socket on it, and then discovered it was pretty much at the end of it's travel. I think that worn studs is a definite possibility and I'm going to check that right now, thanks Bill.
Richard V