alexeck

I _just_ bought a new 2012 GL 350. Accellerating off a light, all of a sudden, heard a bunch of noise, and the check engine light goes on. Car runs badly, but still runs.

I pop the hood and I see a large hose leading into the engine on the front - disconnected. The hose appears to be a main hose leading into the engine. Again, it's directly in the front of the engine, leading into the engine, between the radiator and the engine.

I figure with a bit of elbow grease, I can simply reconnect it.

However, pardon my ignorance, but what exactly does this hose do?

Dealer service is open again on Tuesday, and I can take it in... but if it's such a simple fix, I'd rather just reconnect it and move on!

alx

Take a pic and post here with arrow pointing to problem.

alexeck

ok, here is a pic. This is looking at the car from the front. The hose is a large one. Note I have partially reconnected it already, but have not fully fastened it.

alx

Wiggle it back in, call your dealer and schedule an appt to have the clamp assembly replaced/ checked. You want this one documented

Never seen this one pop. It might be a simple clamp or you might have a bigger issue with over pressure.

alexeck

Apparently, this is the charge air hose into the intercooler. Doing a bit of research, it isn't unusual for these to "pop" off but I wasn't able to find anything with the Bluetec engines. Anyway, I put the hose back on, it clamped on just perfectly, and now the car is running great. Still the CEL but I can go to the dealer and have that checked.

Thanks!

alx

they dont usually pop unless you are overboosting for one reason or another. hence my request to have it documented as it can be the prequel to an expensive repair.

better be safe than sorry.

Fourdiesel

The charge air pipes can, and do, pop off if they are not connected properly. I've not heard of this happening on the 350 but there were some assembly issues on some of the earlier 320s. Dealer fixed under warranty.
Loss of the charge air pipe (from the turbo to the cooler in front of the radiator) usually won't throw a code - but I guess yours did - but there will be a SERIOUS lack of acceleration!

alexeck

Fourdiesel, do you think realistically any damage done to the turbo, engine or intercooler?

alx

No. Just loss of power. Over spinning the turbo (due to lack of pressure on the cold side) for short periods of time especially if you weren't pushing the truck is prolly ok.

But if have cooked the bearings and that shows later when you start running a quart of oil in thousand miles- you want the popped hose documented as a possible cause that will allow you to have a legal case.

So.. Go have the event logged at the dealer so there are no long faces later

Fourdiesel

Unlikely to be a problem from over speed. The compressor wheel was not out in the open where something could have hit it and damaged it (the hose popped off downstream of the compressor). As long as there was oil flow to the bearings there should be no issues on account of this incident.

alx

the hose popped on the pressurized side- intercooler tract leading to 0 boost. no boost (think of it as back pressure for the cold side of the turbo) = no resistance for the turbo equals ability to overspin greatly if hot side is pushed (gas pedal wise).

if you overspin a turbo significantly - no amount of oil will save the bearings.

i have blown an intercooler pipe on a single turbo supra and i destroyed the turbo (cold side impeller got disintegrated and bearings got toasted) from the flash overspin. it took about 30 seconds for this to happen. while this is not the scenario here there is always a risk.

the maximum efficient as well as the maximum permitted turbo rpms are listed on the turbo map for each "stock" turbo. you spin out of the efficiency map- you run hot. you run over the permitted rpms - you destroy the turbo.

Fourdiesel

The operator has almost no control over the turbo rpm achieved. That is entirely controlled indirectly via the CDI control unit calling for more (or less) boost. My comment about not likely to have caused damage was based entirely on virtually the same thing happening to my CDI (See my writeup on replacing the M55 motor).
The bolt (also holds the center of the engine cover) holding the aluminum pipe between the turbo outlet and the charge air cooler broke off [poor installation by the M-B tech]. Without that bolt, there is nothing to keep the pipe from moving forward away from the turbo. And it did! It happened to me when I accelerated to pass a truck on White Pass, WA. I limped 30mi up to the top of the pass when some of the oil coming out of the turbo - normal seepage past the bearing - started to smoke on the hot metal. After a rest, I limped into Yakima, then to Kennewick and then, when it couldn't be fixed because the hardened steel bolt wouldn't come out of the manifold, drove it 100mi home and then 60 mi down to the dealer in Portland.
After all that - and I was asking for all the acceleration the motor would produce several times to climb hills - there was/is NO damage to the turbo, bearings or compressor wheel.

alx

consider yourself lucky. also long term effect on your turbo is unclear.

the cold side of the turbo "pushes" against the pressure in the manifold which acts as an air brake. without boost, there is no pressure, no air brake - allowing the turbo to overspin if you have it floored.

a loose analogy can be made with offshore racing boats- when they jump out of the water and propellers grab air one of the pilots backpedals the throttle so the engines dont overrev while propellers are in the air. it is a similar scenario with the turbos, but they push air instead of water and you dont backpedal the gas pedal thus possibly resulting in overspinning.

depending on many things some turbos are more prone to overspin then others and some tolerate it better than others.