Cold start-up rapping/tapping, goes away after 1800 rpm?
 

Hello all,
New to this list but not to Benz, can someone help? I've got a '87 300TD with 215k miles and the engine has recently started to make a louder than normal rapping noise at idle upon cold start-up. If revved beyond 1800rpm, the noise goes away and it purrs smoothly. Also after driven for a while and warm, the noise is less noticeable at hot start-up.

Any ideas on wht may cause this?

I have used different fuels from different suppliers to eliminate fuel quality issues
I have also run two tank fulls with fuel conditioner/cleaner additive
There are no fuel leaks at the IP or anywhere and all seams buttoned up under the hood. No unusual oil consumption etc.

Have not checked timing chain tensioner or chain slack, but I would assume this type of problems would not go away under load-speed, or am I wrong here???

Help Please


1987 300TD 215K
1986 300SDL 363k

You have a lifter thats starting to wear (tapping) due to blocked oilways proberly caused by combination of age and innapropriate oil or too few changes. When the engines hot the problem is less obvious and at speed general noise means its hearder to hear but its proberly still tapping/ticking quietly.

Mike.

I have the same car, with about the same mileage, with the same "problem". For me, it doesn't happen all the time. Also the frequency in which it does happen has not increased over the 2 years I have had the car. It is a sticky lifter, and this has happened with using both Mobil 1 and reg. oil. I had an independant mech. tell me to not to worry about it. It is fairly common on the 603 engines.

Thanks to all,

It seems that if this is a sticky lifter, there should be someway short of replacing it to eliminate the stickiness??? Rather, has anyone tried or know of an engine flush that is good at clearing out the oil passages/ Or an additive of some sort?

I'm surprised that this would occur on a synthetic oil car, which mine is not...yet.

Also from you experience, has the switch over to synthetic oil cause MORE noticable oil leaks??? I did this once on a Classic Chevy that was leakfree befor on 20/50W, after 1 month on mobile1 she was bleeding alot., changed back to the heavyweigh, and no issues since.

Thanks

Don't use any type of engine flush. What crud it doesn't break away completely, it will loosen. So you'll be driving down the road and this loosened crud become loose and plugs up your oil passages.

It appears that my 603 in a 87 TDT has the same tapping lifter. Only when cold. I have used synthetic always but makes no differance. I am wondering what kind of job it is to change it out?

Hi mileage 603 engines develop noisy lifters, some worse than others probably due to differences in maintenance intervals and the type of oil used.
I replaced all the lifters in my '87 300D and its been very quiet, only a little tapping when cold starts, that goes away completely when warm.
At about $20 per lifter its not a cheap repair (there are 12 of them) but think of all the money/time saved from not having to do valve adjustments! :)
Removing the cam must be done per factory procedure otherwise you may break the cam. As long as your doing that you might want to replace the glow plugs and clean the intake manifold. If you really want to be thorough you could send the head out for surfacing and pressure check and a new head gasket but the question becomes how deep are your pockets?