Hankiss

In my S-class W220 (2005) MB Star Diagnostic shown fault with component M55 which is Intake Manifold Shutoff Motor. I checked the motor by disconnecting the linkage between the motor and the flaps and let it work on itself. I established that, the motor is working OK (the arm moves forward and backward as normal). So I focused my attention on the flaps mechanism. I discovered that flaps are kind of stiff and moving very reluctantly. I pushed them manually few times into Open/Closed position in hope that their movement becomes easy. Unfortunately, they still do not move smoothly. The vehicle was out of use for few month and this could resulted in the above problem. There is no outside lubrication (I think) which may help flaps moving smoothly, is there? The friendly mechanic advised me, to permanently disconnect the motor form the flaps and leave them OPEN at all time. He said nothing bad will happen and I can run the engine with flaps open. I did that and the car is running OK. Now… comes my dilemma, what to do next? Spend a lot of money for new intake manifold with flaps fitted, try to repair the old manifold with repair kit… or leave flaps open permanently and forget about it? I do not understand the full role of the whole mechanism (shutoff motor and flaps) and what possible negative effect maybe created by disconnecting the motor and leave flaps open. Can anybody here explain this to me? I would be very obligated to receive some technical info regarding the above. Thanks and all the best.

ttawd

Hankiss,

I have the same M55 Intake Manifold Shutoff Motor error code on my 2008 E320 Bluetec (W211)-Diesel 642 engine, V6. How did you solve your problem. I was not able to move any flaps like you suggested and as I have seen suggested. I think your engine is a 3L inline 6, diesel, correct? Maybe your shut off motor is in a more accessible position. On the V6 engine, the inlet shut off motor sits in the V of the engine, between the turbo and the fuel filter, very hard to reach area.

Sincerely,
-Mike-

Hankiss

Mike, I’m sorry to hear about your problem. Over half year ago I permanently disconnected the shutoff motor from flaps mechanism. Since then, I’m running the car without major issues with flaps open at all time. I did about 10.ooo miles like this. With old straight 6 cylinder engine, iIt was very easy to disable the link between the motor and flaps. The motor seats on right hand side and it’s easy accessible. Replacing the manifold and flaps is expensive business so in my case W220 2005 may not be worth doing. Your situation is different. Newer car, higher value. I have no experience with newer engines, but I would imagine, V6 engine is more complicated to work with. As you mention M55 hard to reach in your case. Also, quite honestly speaking I’m still not sure what negative effect may be created by running the car with flaps open at all time. I’m sorry can help you anymore and wish you all the best. Cheers, Mark

ttawd

Thanks for the quick reply. It does sound like it was easier to lock the flaps in the open position on your inline 6 cylinder than on my V6. I have driven about 8,000 miles so far like this. The disadvantage is that the car does not accelerate as quickly as before and the RPM will only go to 3000 instead of 4500. I can compensate a little by shifting gears manually, otherwise the car computer shifts gears at very low RPM and acceleration really suffers. I may just fix it, so that I know that it works properly.

-Mike-

Hankiss

Hi, very strange? Poor acceleration and low RPM? Mine goes to full revs range. Did you consult the matter with experienced Merc technician? In my opinion open flaps should not affect the above, but I’m not an expert. Did you run Star Diagnosis on your car? Cheers

Kosterkille

The poor acceleration is a safety mode that your car will go in to if you have a bigger issue with your engine i was told in the workshop today(pro mb). the fuse for m55 was blown and just like u the need to take away the turbo to repair the manifold. egr sucks...its going to cost me about 3000 dollars to repair..but i hope my guarantee will cover it. If u fix it yourself like Hankiss you still need to reset the saftymode-or transport mode or whatever its called to get full power again.

ttawd

I did end up fixing the car. The final bill was $4500 at another mechanic that I trust. He changed both intake manifolds, the little motor that moves the flaps and the faulty oil separator membrane that let oil leak past it into my turbo and manifolds. My car was out of warranty, so I had to pay out of pocket. Some of that bill was a transmission oil flush ($350). I trust the non dealer mechanic much better than the dealer, because the dealer had the car for this same problem a few months earlier, and after charging me $1400 they replaced only the little motor that moves the flaps without getting to the root of the problem. A few months later, my little motor was fried again because they never fixed the oil leak and did not replace my manifolds. They were going to give me a free little motor, but I needed to pay labor again. You can cheat me once, but not twice. So I went elsewhere. -Mike

Kosterkille

Okay.. expensive little story.. I told the mechanic about your case...he just said that he never heard about clogged up air manifolds, he did say that there is a miss in the construction on the v6 with placement of the m55 motor ,cause oil leakage from something(sorry i cant remember what he said,but they will change the gasquet) ends up short circuiting the little ******* and also that it would be a quick job to change it if it wasn't under the turbo..I told him to carefully control the manifold since the insurance company pays the bill and i do not want the same problem in a year or two..yesterday my generator broke down as well which i totally depressing.. Tuesday hopefully everything will be fixed..