Mercedes 450SEL 6.9 engine ticking/noise

[harrycarry250]

Hello all,

I am looking to get some third-party opinions on the source of this engine noise I have been trying to get to the bottom of.

I got the cars timing chain and guides done as well as all hydraulic lifters replaced, long story on the lifters.

Beyond that I cannot figure out what this noise is and neither can my mechanic, I fear future inspection and diagnosis requires opening the engine.

I'll include a link to a YouTube video of my car running. Note; this was taken after 30 minutes of driving home from the shop, highway and local driving. Upon cold start-up the sound can be silent or subdued. There is also a loud exhaust leak you'll here.

https://www.youtube.com/watch?v=TFkaaZfeUj4

Thanks

[daantjie]

Sounds like a lifter tick to me.  As a rule of thumb, a tick @ 1/2 engine speed is from the top end, and a noise equal to crank speed is from the bottom.  So, depending on what your idle is set at (sounds to be idling high maybe with vacuum leak too?), you might be able to nail it down to either bank, or both.  So if you are running @ 600 rpm idle, then a tick @ 5x/second would be top end noise.  10x/second from the bottom.  Bottom end problems are exceedingly rare on the 6.9.  Usually it's the valve train.  Guides wearing out are a well known failure point in these and other Benz motors from the same era.

[harrycarry250]

Thanks for that insight. I have never considered mathematics in my evaluation of the sound.

Considering that the guide rails and timing chain are new along with a newish tensioner (save for the very bottom guide) and all of the hydraulic tappets are new what would be the next item to check?

Thanks.

[daantjie]

When the lifters (hydraulic compensators) were changed, was the preload also checked?  Regardless you would have to pull the valve covers and have a gander.  Feel for loose rocker arms and scoring on the cam lobes.  You will need a "go no-go" gauge to check the preload on each lifter.  Laborious work but you need to have a systematic approach to this kind of troubleshooting.  Also, you need to ensure that each lifter and rocker arm combo needs to go back into the same position as it was.

[UTn_boy]

A few things:  What Daantje said is of great importance.  So bear his words in mind, too.

They hydraulic elements, even though new, won't do their job if the oil galleys that supply them with oil are clogged. This happens often, and usually caused by previous owners having used inexpensive oils. 

When you renewed your hydraulic elements, did you check valve lash clearances and correct any with the proper thickness shims?  There is a special tool used to do this.  It sits on top of the rocker arms where they sit on top of the hydraulic elements.  It's more or less a go-no-go type of gauge.  The problem is that in order to use this tool the oil pressure must be at operation pressures in order to take out the slack in the hydraulic elements.  Otherwise you'll get erroneous readings.  I believe air can also be used to pressurize the system, too. 

The next areas of concern are the camshafts and rocker arms themselves.  Are they worn?  The rocker arms are notorious about wearing. Wear will be obvious to a trained eye, and excessive wear will be obvious to anyone.  Hopefully you took note of their condition while they were out to renew the hydraulic elements.  Also, were the rocker arms out back in their respective locations?   

And last, the valve stem guides are notorious for wearing.  When they wear, the valves will make rattling noises when warm, but not when cold.  Unfortunately, this repair involves removing the cylinder heads, but as old as these cars are getting a valve job is a necessity. I believe someone somewhere on this forum or the M-100 forum wrote up a beautiful post on this particular subject matter.  He was having the same noise that you are.  After renewing the guides and having the valves re-seated the noises went away.  Even my 6.9's make this noise, and I know they need a valve job.  I keep putting it off because of how costly it's going to be.  :/ 

[TJ 450]

That noise does sound very much like a lifter noise, worn valve guides will make more of a ticking/clacking sound when the engine warms up. This sounds exactly like when the hydraulic lifters are not pressurised. I don't think you will need to pull the heads to fix this, but you will need the go-no-go gauge and check to make sure the lifters are not bleeding off and that there is good oil pressure too.

Tim

[TJ 450]

Also, another point to make is that when installing the lifters, mark the spot where the oil supply bore is located, so when tightening you can make sure it is aligned. Apparently if you just torque them to spec, this may not be the case.

Tim

[daantjie]

Also, another point to make is that when installing the lifters, mark the spot where the oil supply bore is located, so when tightening you can make sure it is aligned. Apparently if you just torque them to spec, this may not be the case.

Tim

Hey Tim.
This is not mentioned in the service manual to my knowledge?  When I replaced my compensators I also wondered about this, but the design to my eye was such that the annular will get oil from the feed no matter what orientation you end up with after the 60nm torque?

[Randys01]

my pet subject.!

Fact 1.
I confirm that it does not matter where the lifters end up threaded in the head, the design is such that oil will flow around the annular and into the lifter.

Fact 2.
The lifters maybe new but as has already been highlighted, if the oil gallery and drillings are blocked, the party is over.

Fact 3
If the oil supply to the overhead oil drip pipe is compromised, another nasty awaits us.

Observation 
This engine is making enuff noise to suggest the top end oil feed to lifters and rockers is not right. One cannot eliminate a couple of bad guides but there is too much going on to be definitive. The more obvious sources of noise need to be dismissed first.

Before you run it another minute you need to establish: is the sump full?

Is the top of the motor getting plenty of oil from the dripper line?
- plugs out..fuel pump relay disconnected..coil disconnected remove a cam box and crank the engine
:observe oil is squirting out of the overhead pipe onto each rocker
:yes, even at cranking speed this should be observable
; standby by for a mess.
+ are all the cam lobes smooth?
If this is all OK, you will need to test the static clearance  on the "valve compensating elements" [lifters ]?

Originally this was done by dial indicator and was a real pig but the advent of the so called "go no go gauge" makes it simpler.
I'm assuming someone on your team has sufficient knowledge of this device and how to use it but it will tell you which lifters are not within range. If you have a couple then it is highly likely the oil gallery is partially blocked. Now the job turns messy. All rockers off, all lifters out, all lifters purged and all oil galleries purged. All lifters back in- all rockers back on- and all lifters measured after pressuring the oil gallery. Adjust all lifters to spec.
Put her all back together and start her up. It should purr. I've done a couple of these now BUT it is an exercise in each step must be squared away to 101% satisfaction before going to the next.

This is a day's work to do both banks. BUT you will get an idea of what's going on if you work on one bank first.

btw.......routine mtce required these lifters to be checked every 45000kms using the dial indicator method. I bet none of them were ever done especially when they moved to 2nd and 3rd owners who could barely fill the gas tank let alone a 4hr job at dealer hourly rates! A compounding factor along with infrequent oil changes that gave rise to valve guides not going the distance accompanied by rocker pad failure and ultimately scored cam lobes.

Good  luck.

[daantjie]

Yup what Randy said is the gospel

[TJ 450]

Yep,

About the lifter oil bore, this was just what the guys at the machine shop told me when I had the heads rebuilt, I must admit I suspected it was a non issue as there's plenty of room around there for the oil to flow when looking at the design.

Tim

[Randys01]

Response.
  The oil gallery itself is not a bad diameter but the diagonal drilling in the threaded bore is getting damn small and it then has to fill the annular to progress into the equally mingy port in the lifter. Remember, the top of the motor gets last call on the oil flow. When the motors were new and had heaps of oil pressure and everything was young and beautiful, this all flowed like ambrosia. But there is a quirk in the design which I reckon should have been modified to meet the inevitable.** It is simply this. The oil galleries come to a dead end. They are not a partial loss system, accordingly the nasty sludge builds up at the end of the gallery and slowly works its ugly magic backwards.
If u ever have the chance to look at one of these in situ with all the lifters removed you will see exactly what's going on....a long thin black taper of muck.  Sooner or later it inhibits flow to the lifter or more likely, gets into the lifter where the bleed ports are of nano proportions.

Here's when some of the trouble emerges. A lifter which cannot bleed down or pump up is a lifter that will cause no end of noise and ultimately damage. It becomes inert or static and does not reset itself. so the next thing you know you have lash....clearance between the rocker pad and cam lobe. Once you get slapping in here rather than just following the contour in perfect contact, you start knocking the stupidly thin chrome skin off the rocker and then its steel on steel.......so then we get material transference and start scoring the cam lobe. The noise you hear is only the symptom...not the real complaint.

I am amazed how quickly dirty oil repopulates the oil galleries even with the most assiduous mtce protocols in place.

On one hand it is a design with little redundancy built in........I guess DB never envisaged how their masterpiece was going to be so neglected that it would all come to this. 

** not that they were to foresee this, But I reckon a service bulletin should have surfaced that every time the valves were checked [ every 45K hahaha!}, the Cyls No1 and 5 lifters should have been removed and the gallery power flushed.

Finally...by the time friend Harry Carry executes this complex back to square one procedure, he will feel like Harekari!!

There are no shortcuts and near enuff will not cut the mustard....that's how we got here?!!

Cheers

[daantjie]

Randy, I need to pick your brain on this question which has been bugging me, and other folks (mostly on the currently dead M100 site) have pondered this for a while. With regards the "go - no - go" gauge, there appears to be multiple iterations of this very crucial tool.
In the M100 manual, it specifically mentions a "100" prefix tool for this job, which of course is long since NLA.  Now, the "only" tool still available from Benz is the one used for 116 and 117 motors - 117 589 06 23 00.
The plot further thickens, in that I have come across this verbiage on job # "05-213" - "Checking and adjusting should be carried out with the testing gauge 117 589 06 23 00 with revised measuring groove position".  Furthermore - "Since December 1982, the hydraulic valve clearance compensating elements are adjusted with a revised preload dimension (basic position) previously 0.7-1.9mm, now 1.2-2.4mm).  This is achieved by adding a thicker thrust piece to valve spring retainer".
And lastly - "The revised preload dimension is also valid for all previously manufactured engines 116 and 117, and must be taken into account when checking and adjusting basic position".  Note, it does not mention the M100 here.
Now that we have all that out of the way
It gets more muddled, in that there is a knock off tool widely available, the "Sir Tools" M0024, which states it's for "1976 and onwards V8's":

http://www.pelicanparts.com/More_Info/TOLM0024SIR.htm?pn=TOL-M0024-SIR

Now, this might be a little OCD, but to me we now have 3 different gauges which can be used, and they all might give you a different reading!?

I recall there was a post on the M100 site showing the clear difference between the M0024 and the "117" - prefix gauge from Benz, both in quality of the finish of course, and in the exact position of the measuring groove.

So, to me, the "only" way to determine which gauge we can use for the M100 would be to have an actual 100 - type gauge for comparison to these other 2 gauges?
Calling all cars, who has this elusive unicorn of a M100 gauge, gents..?

[robertd]

HI daantjie

I'll bet it is the "suspension" hydraulic pump running with air bubbles.
typical pump sound.

good luck

[rumb]

I have the 117 tool.  I recall a bit of that m100 conversation, the SIR tool was out of spec. 

I also have .7mm shims circles I had made if you want to buy some.  (need to double check the thickness but I think that is correct) 

The result I came to was to use the new clearance spec, thus use the 117 tool.