Mystery tappity sound is back!!! - PeachParts Mercedes-Benz Forum

compu_85 · #1 12-24-2008, 12:39 AM

So after replacing my vacuum pump on my SDL the "mystery tappity sound", a very harsh metallic clacking coming from the front of the engine, went away. Until tonight. Now all of a sudden it came back. Now granted I only drove the car about 20 miles with the new pump installed, but the noise went away completely when we put it on.

Using a stethoscope the sound is loudest when you listen to the front of the engine between the cam pulley and the ip. I've pulled the valve cover, didn't see any wear on the chain. I gave the timing device a quick glance while the pump was off but not a very through inspection. When we had the valve cover off we looked at the upper guide and nothing looked super wrong. The engine has about 50,000 miles on it.

I'm at a loss for what this could be. Any ideas???

-Jason

compress ignite · #2 12-24-2008, 01:20 AM

["Cringe"]
Any chance you've gotten hold of a "Bad" Vacuum Pump?

compu_85 · #3 12-24-2008, 10:42 AM

Yes, the pump never actually made vacuum. You thinking its just another failed unit?

-Jason

The Gears · #4 12-24-2008, 08:15 PM

I think the ting sound is produced by the vacuum follower (roller) flying off the cam and landing with a clank. I replaced the spring in my pump then the clink sound went away,and stayed away. A new spring comes with a rebuild kit.

compu_85 · #5 12-24-2008, 09:31 PM

Now I really want to take a look at the timing device... I have to wonder if the "track" is screwed up somehow.

-Jason

compu_85 · #6 05-11-2009, 10:21 AM

So I got a shiny new Mercedes pump, but I have a quick question about the gasket. I notice some are simply a regular gasket, but others have a flap on them that would trap oil in the bottom of the pump. Is there a reason for this?

-Jason

compress ignite · #7 05-11-2009, 05:28 PM

Were instituted as a "stopgap" to help catch lube oil for the VP.
On the W124 Diesels the later model engines OM602,OM603 had "Modifications"
to improve VP Lubrication ,so the Dam gaskets were not needed on those.

I don't know if the 350SDL engine had one or not
(Or when ,If Ever,they were "Modified")

GSXR is your best source for info on that!

Please take pictures of your Second VP [The "Fresh" New One]
(If it turns out to be bad)
AND pictures of the Timing Device.

Pictures courtesy GSXR:
1. old style TD (On left) / new style TD (On Right)
2. Dave's destroyed TD.
OH,make sure #3 is not still installed on your TD

compu_85 · #8 05-13-2009, 12:13 AM

Ok guys, I'm at witt's end!!!! Brand new Mercedes logo vac pump installed. Vacuum works correctly, trans shifts great, no tappity sounds.... for 15 miles. Now the sound has returned, same as ever. I am at a complete loss! At this point should I tear the whole front of the motor apart and replace the timing chain?

When we were replacing the pump I felt the timing device and the worble in there felt great... no gouges, nice and smooth.

-J

mplafleur · #9 05-13-2009, 07:33 AM

Is there a reason the assembly basket shouldn't be left installed?

compu_85 · #10 08-09-2009, 01:14 AM

So, I think I overlooked something.

We took the chain tensioner out tonight. There was no oil in it at all. We refilled it (tensioner got hard to press), ran the car for a bit (tappity sound came back), and found the tensioner had no oil in it again. I had done this not long after I got the car and it had no oil in it, and when we messed with it before the tappity sound went away for a while.

So I'll be ordering a new one of those on Monday, hopefully that fixes things!

One question: The FSM states: "It should be possible to compress the chain tensioner quite slowly, evenly, and with little effort after filling with oil". I take that to mean that if I press lightly over a long time the tensioner should compress? I was able to take the thing in my hand and easily push in the piston with my thumb.

-J

jt20 · #11 08-09-2009, 02:41 AM

Quote:

Originally Posted by compu_85

One question: The FSM states: "It should be possible to compress the chain tensioner quite slowly, evenly, and with little effort after filling with oil". I take that to mean that if I press lightly over a long time the tensioner should compress? I was able to take the thing in my hand and easily push in the piston with my thumb.

right. That should not occur on a good tensioner. Think of it as a shock absorber.

not so much a "long time", but slowly and with continuous force... as if you were squeezing oil out of a very small hole from a very large cylinder.

I think you found your solution.

compress ignite · #12 08-09-2009, 03:34 PM

'Tensioner not inexpensive,BUT much better pricing than VP.

compu_85 · #13 08-09-2009, 03:46 PM

Ya I wish I had done that BEFORE I replaced my vac pump

compu_85 · #14 08-14-2009, 11:44 PM

Ok, so I got a new tensioner tonight. Filled it up with oil, installed it, and the noise went away... for about 70 seconds. I pulled the tensioner out and it was almost empty of oil, just like the last one.

I just don't where to go from here. Should the tensioner stay fairly "pumped up" with oil? Could there be a problem with the oil passage that feeds the tensioner? Does it get pressurized or or just splashes?

Thanks.....

-J

compu_85 · #15 08-16-2009, 03:01 AM

Bump. Does anyone know where the oil passage for the chain tensioner goes? Is it pressurized?

-J