BudC

I have a 2011 E550 (3/2011 build date). Recently, I've experienced a problem where the the transmission won't shift into 7th gear when the engine is hot.

The symptoms are similar to the delayed shift when the engine is cold. Mercedes delay the shift to heat up the catalytic converter. This only lasts for a few minutes at the most and is normal.

My problem is that this occurs when the engine is hot and won't shift up even after driving several miles at 50 MPH. I don't know if this is a problem with very hot weather since I live in Arizona.

If I take the car out with the engine cold, drive it until the engine is warm, park the car for some minutes and then restart the car and continue driving, it won't shift into 7th gear.

Now here is something interesting and works every time. If when I'm driving, I turn the A/C compressor off for a few seconds and then turn it back on it will shift into 7th and act normally from then on.

All of these symptoms are pretty consistent since the weather got hot. The problem didn't occur last year.

I recently had the car in for service and there were no outstanding Service Bulletins for my VIN number. I didn't mention this problem at that time.

Has anyone had a similar experience or have an idea about what could be wrong? It's as if there is a bad sensor somewhere.

HBerman

Yes, my build date on my 2011 E550 is 6/10. I've had the issue since forever regardless of numerous updates of the TCU, ECU, etc modules. Turning off the A/C for 5 seconds is enough restore proper operation. The problem happens if the outside temperature is above 87 degrees F. I've no idea, nor does the service department why this occurs, but this is the third summer now where it is evident.

khelms98

I have a 2010 E350 and my transmission acts jumpy (a better word escapes me at the moment) for the first mile or two, or perhaps during the first cycling through the gears, when the ambient temperature is in the upper 80's and above. After that, it acts normally and shifts normally.

I am not certain if my transmission is shifting into 7th gear as I haven't paid that close attention. I do, however, notice a droaning noise only present in higher temps and goes away when the A/C is turned off. I'm not sure if there is some fan running at high speed but for the first few miles of driving, when I'm coasting to a stop and this noise is present, it almost feels like a stick shift when it downshifts somewhere between 20 and 30mph. It's definitely A/C related but I don't think it's a bad compressor because it's not a whine that typically indicates a bad compressor (I know because I had that on an '08 ML350). Perhaps it's a fan running to assist the A/C in cooling down a very hot interior, but I'm not sure.

Again, after a few miles of driving this noise and odd shifting pattern goes away and everything is completely normal and the transmission shifts as intended, with a doubt.

Do either of your E550's exhibit any of this behavior?

BudC

Thanks for the feedback guys. Today, after driving and then parking for a while, I started out again with the A/C off. It worked OK.

The noise that can be heard is the engine fan. Based on my past experience, it comes on at a higher speed with the engine is hot and the A/C is on.

I can live with the problem so long as I know it's normal for this car.

BudC

Mercedes delays complete shifting when you first drive your cold car. This is to help heat up the catalytic converter. Even my 20 year old 300E does it.

The noise is probably the engine fan. I generally sounds louder when the A/C is on.

I believe what we have with the E550's is due to the very low rear end gear ratio. It's 2.4:1 on the E550 and something over 3:1 on the E350. In other words, your E350 already runs an a higher RPM for a given speed. On the E550, I believe that it's designed to keep a higher RPM when the engine temperature is higher than normal. It's like keeping your engine idle revs up when you are sitting in traffic on a hot day.

HBerman

Yeah, that was when the cooling fan was directly driven off of the fan belt. No need with the electric fans of today and the temperature controlled modules.

BudC

Revving the engine will get more coolant through the radiator unless the car has an electric water pump. I don't know if the 2011's have them.

HBerman

Ah, true enough. I don't believe that the water pump is electric on the V8

khelms98

Not to highjack, but does my 2010 E350 have an electric fan and a belt driven fan of some sort? I know I hear the jet engine fan kick on and off when idling and I'm assuming that's the electric fan....so you guys are saying the droaning sound I'm hearing is from the separate belt driven engine fan, or no? Tell me once and I'll have it. Thanks, and I apologize for my ignorance.

BudC

Raise the hood and have a look. You will see a gap between the front of the engine/serpentine belt and the fan. The fan is electrically driven. It can still be pretty noisy, especially from outside the car.

khelms98

Should this fan speed and subsequent noise increase or decrease with rpm at low speeds on a hot day and be affected by the A/C either being on or off?

BudC

The fan speed should be independent of the engine RPM but could be affected by the A/C being on because it could cause the engine temperature to increase. How many times have you sat in traffic on hot days and turned the A/C off to reduce engine temperature? How many times have you climbed up long grades with an underpowered engine and turned the A/C off to ease the load on the engine?

khelms98

Thanks! Maybe what I'm hearing isn't normal then because this droaning-type noise I hear changes with engine RPM and transmission shifts, but also occurs if I rev the engine at idle ( > 1200 rpm). It goes away if I turn the A/C off or after I've driven a few miles and gotten up to speed with the A/C on. Definitely RPM dependent and A/C related.

My dealer has already recommended a belt change since I'm at 60k miles and also have a slight chirp at idle in the colder months until the engine gets up to temperature. Perhaps this could all be related. I don't know, but I'm out of warranty and don't want the dealer spending hours and my $$$ hunting for a problem, only to tell me there's not a problem. Thanks again BudC and I'm sorry for imposing on your thread.

Yosheego

hahaha! i thought i was crazy! Here is my issue. I notice it happening to me most when the temp outside reads 90+. I feel like I'm in a lower gear when I'm going around 40+. I hit the right paddle shift once and my rpm drops, then it bounces back up right where it was at, as if i downshifted again...if i drive without accelerating the gas or dropping it, it would then automatically shift back to normal, usually about 1/4 of a mile. if i'm at a stop and go...yes, it's horrible, but Mercedes says it's normal...I have 22k miles on it and it's been happening ever since i got my car. At times, I'm driving around 70+, my RPM seems normal, but I feel like I'm in a higher gear. Car doesn't jerk, but you know how you have a higher gear, you can feel the car kind of have the engine brake? so yeh, i gave up on it...this is somewhat OP having too or similar?

BudC

Just watch the Tach. My car usually runs at about 1,100 RPM when I'm driving round 45MPH. When this condition occurs, it's probably at least 500 RPM higher than that.

Yosheego

your right, it's almost at 2000 rpm...Lemme see if i can get a video on it to show you guys...

Yosheego

okay here is the video of what's happening...



2nd Video



so there you go...sometimes, i'm in the parking lot looking for a space to park and my RPM is at 1500 moving at 5mph or less..

Pretty much gave up on saying there is something wrong. It eats up so much gas when i'm in a stop and go traffic.

BudC

Turn the A/C off for a few seconds and then turn it back on. Works every time for me.

Yosheego

I haven't tried it yet, but I'm sure it will work since it does for others. Stupid how we have to do that.

Yosheego

Been awhile, but it solved the problem momentarily after I turn off the A/C. But it's freakin' 100+ here in Louisiana, so there is no way I'm driving around with it off, especially with my little one in it. I have forwarded the problem to a MBUSA people. Since the dealer told me it's normal, which we all feel it's not. I got an email today from someone saying that they will be contacting me about this issues/concern on 8/8/12.

BudC

I found that if you turn off the A/C, you can use the paddle shifters to up-shift. After that you can turn the A/C back on.

I agree that it's ridiculous to have to do this. It's not our imagination, it's a real issue.

ttoE550

I have had this happen to me now several times over the past week or so. I had never noticed it before, and probably would not have thought twice about it if I hadn't read this thread when it was current.

Next time it happens to you pay attention to the temperature of the air coming out of the vents. In my car, a few seconds after it happens (maybe 3 seconds, but less than 10 seconds I think), the air from the vents turns noticeably cooler. I think it is the a/c kicking into overdrive to cool the car. Maybe the drag on the engine is sufficient to require a downshift to avoid sluggishness or possibly a near stall, neither of which is good. In fact, the computer might delay this mode until the engine has warmed up (perhaps the cats too) enough to handle the extra load and/or to promote environmental concerns - an engine is environmentally unfriendly when cold.

I haven't tested this but you might even be able to recreate it with a warm engine by setting the a/c to max cool even when the engine is warm.

I wouldn't be concerned. But I've driven more than my share of underpowered 4 bangers with manual transmissions that, when in a high gear, do a nosedive when the a/c compressor starts.

BudC

It appears it only occurs on E550's and not on E350's which eliminates the argument about power requirements.

It seems to occur in very hot climates and only after parking the car with a hot engine.

The difference between E350's and E550's is the differential gear ratios.

It's about 3.11/1 in the E350 and 2.4/1 in the E550. That means the big V8's are turning over more slowly than the V6's. Could it be that Mercedes are trying to pump more coolant through the radiator by increasing the RPM? It's like sitting in traffic on a hot day and you put the car in neutral and increase the RPM to keep the engine cooler. It's probably not a problem with the 2012 V8's because I believe they have electrically driven water pumps that are independent of engine RPM.

This business not only generates poorer fuel economy but (at least) in my case, it's a distraction to my driving when I'm trying to turn the A/C off and on to get the transmission to shift into 7th gear.

I would like Mercedes to explain what's going on and why.

Yosheego

yes, BudC is right, this only occurs in hot climates. During the winter, I don't have this problem. Whatever it is, I'm averaging 13.8-14.2 mpg city, guess it's okay for being V8 monster.

mambrose23

Happened in my '11 and also in my '12 550