606.910 Resonance Valve vane BROKEN twice! - PeachParts Mercedes-Benz Forum

markg612 · #1 01-20-2010, 11:07 AM

Has anyone else out there seen this yet?

The vane on the shaft has fatigue cracked and broken off twice in 20K miles. See photos below, the center and right pieces are what remained with the shaft, the left piece floats around in the intake and vibrates! (Vane is aluminum, this is the on the bottom of the intake vs the bottom of the charge tube. 1995 124.131 E300D)

Part 606 140 00 31--never superseded since new in 1993!

Talked to MB with no real answer, surprise!

Ideas?

Jeremy5848 · #2 01-20-2010, 01:43 PM

Looks like a fatigue fracture. Is there visible wear on the inside of the intake where the vane rotates? Does the vane turn smoothly? With the charge tube removed you should be able to see the vane. So long as nothing gets sucked into the engine, it would be safe to idle the engine and watch the vane. Does it vibrate back and forth, maybe due to an electronic or vacuum problem?

Could also be due to external mechanical vibration -- are your motor mounts in good condition?

markg612 · #3 01-20-2010, 02:17 PM

Looks like a fatigue fracture. AGREE WITHOUT QUESTION

Is there visible wear on the inside of the intake where the vane rotates? NO

Does the vane turn smoothly? PERFECTLY SMOOTH

With the charge tube removed you should be able to see the vane. So long as nothing gets sucked into the engine, it would be safe to idle the engine and watch the vane. Does it vibrate back and forth, maybe due to an electronic or vacuum problem? WIL CHECK

Could also be due to external mechanical vibration -- are your motor mounts in good condition? 36 MONTHS OLD--VERY SMOOTH.

Jeremy5848 · #4 01-20-2010, 05:08 PM

A fascinating problem (easy for me to say!). If you see no vibration at the vane with the engine idling, crossover removed, then I would next try putting a tee in the vacuum line at the resonance valve, run the line into the passenger compartment and put a vacuum gauge on it. Then watch the vacuum level while you drive (being careful not to become distracted, of course).

As a last resort, price a complete resonance valve at FastLane and, if within your reach, replace it with a new one.

Jeremy

Number_Cruncher · #5 01-20-2010, 05:21 PM

I would imagine that the natural frequency of the centrally supported flap in bending will be quite high, and I struggle to see how normal engine vibrations could cause a problem.

I wonder if the problem might be linked to the possible leakage of exhaust gas back into the inlet. If the valve were subject to combustion or exhaust pressure pulses from the rearmost part of the manifold, these pressure waves might be the source of the repeating excess stress which caused the fatigue cracks to grow.

This makes me think that perhaps I should look closely at the flaps in my OM606, although it's now 50k miles since I repaired the inlet valves.

markg612 · #6 01-20-2010, 06:23 PM

Jeremy, N_C

I'm thinking the pulsing is the issue over engine vibes as well. The head scratcher here is where the opposing pressures are coming from, OR, back to the the valve recession theory--Could startup cough back into the intake be "working" the vane?

Jeremy5848 · #7 01-20-2010, 07:38 PM

The intake system on the OM606NA engine works by 'tuning' the apparent length of the intake using the resonance flaps. If something happens to cause the vane itself to resonate in the air column, it might vibrate itself to death. Since this is not supposed to happen, you need to look at the entire system from the air filter to the head and see if something has changed to cause this apparent vibration.

Incidentally, if the flap is vibrating due to some unwanted resonance in the air pipes, it might cause a detectable fluctuation in the vacuum to the resonance flap in question.

By "changed," I mean more than any modifications that you have made; even if the car is still box-stock, an accumulation of soot and oil from a still-functioning EGR valve might change the internal shape of one of the air pipes, thus causing an unwanted resonance.

When I took my '96 apart to clean the intake pipes as part of defeating the EGR valve for testing purposes only, I discovered that the two PCV ports on the #6 cylinder were completely blocked with carbon and oil. Additionally, the plastic/rubber tubing that directs the crankcase gases to the 6 cylinders were old and hard and were leaking oil all over the valve cover. (Because of the plastic cover of the OM606 engine, this is not normally visible.) I also found that the intake ports were partially blocked by the mix of oil and carbon from the exhaust gases introduced by the EGR valve.

I ended up replacing most of the PCV plumbing, blocking the EGR valve at both ends, and cleaning the intake manifold and all of the flaps of accumulated crud. With the EGR valve no longer working, the inside now stays relatively clean. For some nasty "before" pictures see the first post in this thread.

Your '95, being a W124, may not be as electronically sophisticated as the later W210 models. In particular, I do not think your car has a port for what is now a standard code reader. In '96 and later Mercedes diesels, a problem with the flaps will set a code.

In any case, I recommend going through the intake system from beginning to end, making sure it's as close to factory-new as you can get it. You don't necessarily have to replace anything other than the broken flap but make sure everything is clean and correctly connected.

BTW, can you buy just that vane or do you have to buy the entire assembly?

Jeremy

markg612 · #8 01-20-2010, 08:00 PM

Nice post Jeremy--

No mods, I'm a stock guy always and forever.

The nature of the resonance valving design would have to include some allowance for vibration and the effects on the valve vanes, but obviously not if they break off from work hardening and fatigue.

I boiled out the entire intake system 3 years back and everything you mentioned regarding the plastic plumbing has been renewed and cleaned. The only thing I couldn't do justice with was the intake ports in the head--Considering I didn't pull the head, it was difficult to do more than scrub, vacuum and air out the mess in the intake ports.

Both valves test operate perfect, no drag, nice and tight, etc., etc.

Re vane only, not a chance, only the whole valve. $279! Not available from WorldPac or any other non dealer source either.

Jeremy5848 · #9 01-20-2010, 08:53 PM

Interesting. Sounds like you did everything I did as regards cleaning of the intake system. Wish I had another suggestion but other than teeing into the vacuum line at the resonance valve and watching the vacuum level for rapid fluctuations, I'm not sure what to suggest. Anything fast enough to cause work hardening of the flap would probably be faster than the response time of the mechanism inside an ordinary mechanical vacuum gauge so you wouldn't see anything.

How about putting a voltmeter on the electric valve that regulates the amount of vacuum sent to the resonance flap actuator? That should be a DC voltage, probably 12 volts or less, that is turned on and off by the electronics. The flaps open and close as a function of engine RPM, throttle setting, load, etc. If something was wrong in the electronics, it might send a high frequency signal to the electric valve, which would make the vacuum to the resonance flap vary rapidly, which would cause the flap to flap so fast that it might eventually break. I agree that I'm really reaching here but don't know what else to suggest. If the signal to the electric valve changes fast enough you could see it with the AC setting of your voltmeter. It would also show up on an oscilloscope if you had access to one.

tankowner · #10 01-21-2010, 12:25 AM

Hmmm. Interesting post. The resonance flap in the crossover in my '95 E300D is completely gone - broken off at the base of the shaft that the flaps attach to - has been that way since I bought (didn't discover it until later). I have always suspected that someone intentionally broke it off but wasn't sure why. Maybe not though. I was going to replace it but the cost of a new replacement is something like $250 I think so I thought I would wait to see if I ever come across one of these at the pick-n-pull. Anyway, I might have some pics somewhere I can post.

longshore1 · #11 01-22-2010, 10:25 AM

Mine vane breaks off almost every year, I have replaced it with a home made ones of sheet metal three times, they all have broken off in the same place. One blocked the intake port. Seems to run fine without it.