Intermittent tapping.......300 SDL.... - PeachParts Mercedes-Benz Forum

Plantman · #1 12-01-2003, 07:02 PM

The car is running perfect and I have no complaints.

I am however, very anal about noises,taps, etc.. that do't seem normal.

My SDl has a slight tap that comes and goes. It will come along for no apparent reason, then disappear and reappear without any type of warning whatsoever.

The oil pressure is constant and the maintenance has been religious.

It sounds just like a lifter in need of adjustment on a gas engine.

I was thinking about checking the injectors, but I figured if it was an injector, it would be more constant. This little tap comes and goes within seconds sometimes. Other times it will linger for awhile, then go away.

Maybe I'm asking too much of a car with 325,000 miles, but I figured I'd ask.

Thanks

DslBnz · #2 12-01-2003, 07:42 PM

Ditto, here. Anyone know what it might be?

zbenz · #3 12-01-2003, 07:52 PM

It is most likely one of the hydraulic lifters. Try running some synthetic oil through it for one or two changes. Made my noise dissapear as mysteriously as it came. Althought the cracked head made it even quiter.

sixto · #4 12-01-2003, 09:13 PM

Could also be a bad serpentine belt shock. In my experience it's the end busings rather than the shock itself that fails and causes tapping and knocking noises.

If it is the lash adjusters, try Mobil 1 although it can take up to a year's worth of driving for the noise to go away. Those things are a major PITA to replace and new ones can be tappers as well.

Sixto
95 S420
87 300SDL
83 300SD ... $1100, see cars forum

turbodiesel · #5 12-01-2003, 09:18 PM

It's actually injector knock. It has come and gone in my car forever. It's definately not the valve train. It should sound like a hollow thud, like a hammer hitting the inside of the valve cover.

Plantman · #6 12-01-2003, 09:34 PM

John, the tapping I am talking about is not the same one I heard when I picked it up. That was much more pronounced and constant, until I got on it pretty hard. As you recall the car had been sitting for awhile. That injector knock has never resurfaced.

This "tap" is a lot less pronounced, yet it is distinctive against the backdrop of all normal diesel sounds.

I was thinking about trying some synthetic , so we'll see.

Thanks

turbodiesel · #7 12-01-2003, 09:44 PM

I know the type of noise you are referring to, it will come on then stop all in a few seconds. I have always thought that to be injector knock as well.

When the injector knock came in my car, out of nowhere, even after a 200 mile trip and I got on it real hard, the knock still did not go away.. it came and went as it pleased and no amount of hard driving would take it away. Before anything, I would try a bottle of Redline diesel additive. Used it many times in that car.

DslBnz · #8 12-01-2003, 10:05 PM

That's right!

My tap-tap-tapping noise was very unpredictable. Would not go away at higher engine speeds. It occurred sporadically when the engine was warm. Now the car's fine, and relatively quiet. Needs a beltshock though, now.

Car's great. Its never performed better.

gsxr · #9 12-01-2003, 11:14 PM

Lifter noise is VERY common on the OM60x engines. It will be related to engine speed, but NOT engine load. Can change with temp and be intermittent. Use Mobil-1 15W-50 for a few oil changes and see if that helps. On my sister's 1987 300D, it cured it in days - she was pretty happy about that. When the lifter(s) get bad enough, synthetic won't help, you'll need to replace the collapsed lifter.

Belt shock noise doesn't change with RPM but may go away at certain RPM's as the vibrations & harmonics of the belt change with engine vibration, etc. This is simple to test - at idle, use a broom handle to press *sideways* against the belt shock. If it's the source of the noise, it will get silent when you press on it. BT, DT. Only use an OE (Genuine Mercedes) belt shock, yes at twice the cost, unless you really enjoy changing aftermarket ones every 20kmi.

A hard noise that gets louder under load could be "nailing", which is sort of like pinging/knocking on a gas engine. Diesel Purge should help or cure it, if not, the injectors needs to come out for a pop test (pressure & spray pattern).

My money is on the lifters - that is the most common, and luckily it's an easy cure most of the time. Don't use SynTec, Rotella, or Delo "synthetics" - use Mobil, Amsoil, or RedLine (and don't use the 0W-40 stuff either).

HTH,

airfoill · #10 12-02-2003, 10:17 AM

I have the same exact problem with my 300SDL. It only occurs when the engine is cold and goes away when it is warm. It is annoying to hear but it is definitely hydraulic lifter noise coming from one of the lifters.

Also, my 300D 2.5 Turbo which has a 60X. derritive engine appears to be developing the same lifter noise.....ever so slight lifter noise but I can definitely hear it.

My question: Has anybody on the list ever tried replacing these hydraulic lifters and do you need special tools to do so. It appears from some of the drawings that I have seen that one has to remove the camshaft to get at those little guys. I would like it try it myself only if it is possible with common tools.

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo

gsxr · #11 12-02-2003, 11:22 AM

Herb, perhaps you're not reading what I posted, or maybe you're already using synthetic. Please try Mobil-1 15W-50 before replacing lifters. Now with that out of the way:

No special tools, other than a good size magnet to pull the lifter out. You do need to pull the camshaft. You must follow the factory procedure for the cam removal (and installation!) exactly, or you WILL break the cam. The manual also has a procedure to test the lifters so you only need to replace ones that are collapsed - assuming they didn't quiet down with synthetic lube. They cost ~$25 each, so you probably don't want to be blindly replacing all 10 or 12, unless you have a spare $300 burning a hole in your pocket (which would be much better spend on Euro lights, window tint, or some other item with higher ROI.)

HTH,

Plantman · #12 12-02-2003, 12:25 PM

gsxr,

I will be trying the synthetic later this week.

Funny, I have been in and out of the car all morning and it hasn't made the tap yet.

Maybe it takes Tuesday's off.

michakaveli · #13 12-02-2003, 12:43 PM

Mobil 1.. What about Delvac 1?

Rick Miley · #14 12-02-2003, 01:08 PM

Better, but harder to find. Actually, I think Mobil has a distributer that carries it in Miami or Ft. Lauderdale. Plantman, you might want to check that out. I use Amsoil 15W40 heavy duty marine and diesel engine oil because it's less expensive and easier to get than Delvac-1.

gsxr · #15 12-02-2003, 01:11 PM

Delvac-1 is great stuff but can be hard to locate - usually you need to find a Mobil distributor near you, and it's expensive - $20-$23 per gallon.

Amsoil 15W-40 is also great stuff if you can get that, and at "dealer" price, it's pretty reasonably (about the same as Mobil-1 though after shipping & taxes). RedLine makes fantastic oils as well but they're pretty spendy, in the $7-$10/qt range IIRC. Any of the above are worth trying before yanking lifters out. (Just remember NOT to use the cheapo SynTec, Rotella, or Delo "synthetics".)