Questionable timing chain 450SL....?

I was just reading a thread over in Tech about a sound an Indy reported to his customer after starting his engine (sounded like timing chain slap) and suggested new timing chain.

Every once and a while, when I start my 80 450SL, I hear a real loud noise briefly that goes away a second or two after the engine starts. It sounds serious, but the noise is so brief, I cannot explain the sound very well and would not rule out something to do with the timing chain etc.

I have never examined the timing chain or chain rails, or tensioner. How would I go about to inspect for worn chain? .............BB

[Walrus]

I suspect you have a tensioner that is leaking down from what you have described. If the noise is apparent after the car has set for a spell (like overnight or all day), but not present when the car has set for a brief time, then I would suspect the tensioner. If the noise is present any time the car is started, regardless of time between shutdown and start-up, then I'd be concerned about chain/guides, etc.

You did not mention how many miles are on your current chain and guides/tensioner. Conventional wisdom is to recommend changing guides and maybe chain every 100K miles. I have read of original equipment guides found to be cracked and or broken at mileage above 100k, but I have not read or heard of earlier failure. Time is also important in the lifespan of plastic guides (don't know about the '80 model).

Perform a search on the timing chain topic on this board... You should find a wealth of information as this topic has been discussed many times at length.

If your problem is only the tensioner, it is relatively cheap and easy to replace...

Good luck!

[jireman]

Originally Posted by BusyBenz

I was just reading a thread over in Tech about a sound an Indy reported to his customer after starting his engine (sounded like timing chain slap) and suggested new timing chain.

Every once and a while, when I start my 80 450SL, I hear a real loud noise briefly that goes away a second or two after the engine starts. It sounds serious, but the noise is so brief, I cannot explain the sound very well and would not rule out something to do with the timing chain etc.

I have never examined the timing chain or chain rails, or tensioner. How would I go about to inspect for worn chain? .............BB

this is the first time I've posted, not sure if it's done right? pull the valve covers check the pasanger side cam about have way back and see if the cam lobes look like the ones in frount. the slids on both sides sould not have much wear. This is good place to start. then check the cam gears if the teeth are sharp your chain is warn also. good luck Jim

Thanks guys for that input. This sound has only occurred maybe 6 times over the past 5K miles, the amount of total miles I've put on this car, which has a broken odometer (178K) and nobody knows actual miles?

I don't think I've ever heard this sound on a cold start up, only when I've shut it off, after full warm-up, to run into a store for a few minutes, etc.

I'll do an inspection and see if the rails, chain, tensioner, etc, are worn. One other thing to note, the engine mounts are shot on this car, but I've never seen the engine move, even when flooring it in park. But it may be possible because of one of the cylinders compression is 25 lbs different from the rest and upon start may shake the engine thus making the sound I hear.

[Roncallo]

Originally Posted by BusyBenz

Thanks guys for that input. This sound has only occurred maybe 6 times over the past 5K miles, the amount of total miles I've put on this car, which has a broken odometer (178K) and nobody knows actual miles?

I don't think I've ever heard this sound on a cold start up, only when I've shut it off, after full warm-up, to run into a store for a few minutes, etc.

I'll do an inspection and see if the rails, chain, tensioner, etc, are worn. One other thing to note, the engine mounts are shot on this car, but I've never seen the engine move, even when flooring it in park. But it may be possible because of one of the cylinders compression is 25 lbs different from the rest and upon start may shake the engine thus making the sound I hear.

You cant check engine mounts by flooring it in Park. You must have your foot firmly on the brake and give it about 1/2 gas in Drive to chack the left engine mount and R to check the right engine mount. Even if the engine mount id blown you will only see limited travel ove the engine since its motion will be limited by the engine shock.

John Roncallo