ML350 Nearly Catastrophic Valve Train Damage - CAUSE - Intake Manifold Flap READ

[jc300e]

Forum Readers:

Thought I would share with you all my latest experience with the '06 ML350. M272 w/ 158K miles.

Symptom: - Sudden and harsh misfiring, CEL flash and engine shut off.
Warning: - NONE - no previous drivability issues, no chronic CELs
Initial Findings:

• Plugs Good
• Coil Packs Good
• SDS indicated multiple misfires
• Compression test - All good except for #5 Cyl - read "0" compression
• Borescope on #5 showed 1 intake slightly open/misaligned compared to other
• Removal of Valve cover showed rocker misaligned off cam lobe
• The Scope also showed the Piston and cyl wall to be damage-free

Further inspection found the dislocated rocker seriously scored and damaged the cam, valve guide and top of valve. This required the removal of the left cyl head to R&R the valve. On top, a new left intake cam, spring, rocker, guide, etc...and all the trimmings.

PLUS - in the breakdown, requiring the removal of the intake manifold, it was found that the left side tumble flap actuator was broken on the exterior of the manifold, possibly indicating that the internals of the tumbler malfunctioned, causing a piece of the flap to be sucked into the #5 cyl, momentarily disrupting the valve.

After inspecting the internals of the old manifold, indeed that was the case. The left side tumble flap had broken into 2 pieces, flopping freely inside the manifold. Compared to the right side flap, which remains uniform in its structure and motion, something in the left side flap had disintegrated, supporting the notion that a piece could have been sucked into the #5cyl intake port. In fact, the point at which the flap was most loose was directly above the #5 cyl.

Here are a new photos for your entertainment.

Plastic in an Engine? Good idea? Bad Idea? Did it save me from a total disaster or cause this extremely expensive situation?

I can only say good things about the team at RBM of Atlanta for the way they helped me and kept me in the loop. Forum-folk are not usually the typical client. They entertained every question, walked me through each step and treated me fairly on parts prices and labor rates.... Let's hope the tech followed his MOPs and the torque wrench was dead-on

Thanks for reading!!!
Jeff

[97 SL320]

Good descriptions and pictures.

The proper way to fix is lifting the head as they had done. The "gas in the tank is worth more than the car " / " I'm fixing my own car and will risk it" fix would be.:

Lift the intake, remove plastic from the intake valve, scrape / polish off the soft metal transfer on the cam lobe, inspect the rocker roller for damage ( the rocker looks like it could go again ) replace the intake flap system.

This kind of fix would last as the cam is pretty hard and the rocker body soft. However it is unlikely that a shop would risk actual or perceived liability if something else failed down the road.

[Brady]

Hi I've noticed this post is from 2015 and it's now 4 years later, just wanted to say I have the same issue, fortunately mine hadn't gotten scored and just had some surface scratches so all the parts were still fine to use, sent my car to the shop to get diagnosed after swaping plugs and coils, checking fuel pressure and timing. Got a call saying no compression in cylinder 4, all said and done. I got it in my driveway, pulled the valve cover off and saw the exact same issue, I haven't pulled my intake manifold off, not sure if I should even worry about it. If you get this would love to have an input from you about wether I should take it off or not, ive also thought about buying another one and taking the plastic out.