echo512

My 2008 E320 Bluetec ate a belt yesterday, it went something like this:

1) Noticed a faint squealing sound.
2) Started seeing white smoke coming from under hood
3) squealing stopped, battery warning red light on dash
4) power steering lost
5) car continued to emit white smoke from under hood for 30 secs after

I was in my neighborhood when this happened, so I was able to get the car back home safely (took less than a min). Car had only be on less than 1-2 minutes as well.

This is the 3rd time belt had issues.
First time, I changed before breakage ~88k miles
2nd time, I changed when it broke, at ~130k miles
This time, it broke ~137kmiles.

All the pulleys spin freely/smoothly, EXCEPT for the AC/Compressor pully, which I can't turn by hand at all.
I don't know if this is normal (I didn't check last 2 times). IS this normal? or is this the issue?

IF the AC/Compressor is the issue, could this just be issue with the pulley/bearing and is this replaceable?
Or Is this a full ac/compressor unit replacement scenario?

Thanks for any feedback!

CaliBenzDriver

Good job pining down your bad compressor. The pulley not spinning means it's a no-clutch always on proportional valve compressor.
You don't even have the option not to use it spins with engine. I think yours is done for... new unit!

The thing is compressor failure usually calls for extensive work: Condenser, Dryer, Pressure SW, TXV, Evap + Hose cleaning.
Any spec of junk left in the circuit will set you back to square one.

echo512

Ok, some updates:

1. Compressor definitely bad. It was seized up.
2. Reclaimed/flushed A/C system
3. Replaced Compressor/dryer/expansion valve
   1. Replacing compressor wasn't bad, but I had to purchase a few sets of extensions (compressor inlet/outlet port) 6mm hex sockets for 3/8". I had E torx sockets for bolts already.)
   2. Replacing dryer was super easy. T25 star socket for 1/4"
   3. Expansion valve is under wiper cowl, wiper assembly. I had to buy a "puller" for this ($20). The drivers side arm was narrower than the passenger side, and I had to get creative to get the puller to work (used scrap pieces of metal).

Held vacuum -30mm Hg well.

Couple of notes for Recharging/adding r134a that was interesting.
1) The car's AC computer HAS TO BE reset so that the compressor will turn on. This is not something you can do with a generic scan tool. I purchased a iCarSoft MBII to reset. (~$100)
2) I purchased vacuum and gauges. Worked great. (<$100)
3) Cans of r134a I bought were a bit of marketing fraud. Cans list weights such as "Net 12 oz, 340g".. In the case of the w211 bluetec, full load is 0.95kg. You would think, oh, I need 3 cans, but only partial of the 3rd. Thus I bought three cans. But when I got home, I weighted each can, and each can was 12oz/340g. Was puzzled, as I'd think that each can should have been more than that because of weight of empty can. Anyway.. I didn't think much about it, and proceeded to charge the system. After the first can was empty, I weighted that, and it was exactly 100g.. This meant that each can only had 240g of r134a. Thus I actually needed 4 cans.
4) Cans of r134a I purchased, had "self-seal" technology. The tap I had wasn't "self-seal" friendly. I had to learn how to pierce the can (hold up close to ear while turning the *** to know when), and then of course, purging the line proved that it flowed ok. If it didn't flow, then I fiddled with the tap valve to find the "golden" spot. I wish I had a tap that was a no brainer.
5) took a LONG time to load it. But definitely turn your A/C on max, fans, all. Open all the doors so cabin temp remains higher. I warmed the bottles of freon by holding them by the engine fans.
6) In all, took me about 2 hrs to load in 3 cans (which again, isn't enough). Some of it was 1st time learning issue with can tap..

Well worth it. Spent overall ~$750 in parts (and got new tools!), where I was originally quoted $2500.

I'm attaching all docs I used.

ot1

I have a CPS CC-700 refrigerant scale, it is the type where you rest a 30lbs cylinder on the scale portion of the unit. As you fill your AC system it reads out how much refrigerant has left the cylinder. My AC requires 2.15 lbs according to the sticker on the hood, converted into ounces that is 34.5 oz. I am glad I don’t have to mess with individual cans anymore. My evaporator temperature is 34.5F with a freshly charged system.

ot1

If I am understanding you correctly between the 1st and 2nd belt change the car was driven only ~42,000 miles and between the second and third belt changes only 7000 miles.
Even though the belt tensioner pulley may turn freely, it may not hold the tensioner pulley angle true. When this happens ribs on the belt will begin to peel away. You can verify this tracking by looking straight down on the belt while the engine is running, if the belt is not tracking straight, the belt will have a wobble/drifting in it which you can notice by looking straight down on it. This can put a side load on any pulley that has grooves, could result in those bearings to fail prematurely.

echo512

Issue was definitely A/C pulley seizing up. I did look at the alignment of the belt after replacement, and it seems to be spinning quite well aligned.

As far as second belt dying at 42k miles, I had attributed that to my passenger side turbo charge tube leaking (which I subsequently fixed). The slit in the hose was spewing oil sludge all over the front of the engine, including belt/pulleys/etc.
It seems to me that this motor has so much torque, that it is often killing the engine mounts (I've changed my mounts twice now), and each time, the turbo hoses are prone to failure.

ot1

I have 192700 mi, changed my engine mounts only once at 139252 mi. An intercooler hose is cracking? Which side?

echo512

passenger side. Crack/slit near the coupling attaching to engine.

Either that or bad mechanics creating future work.

ot1

bad mechanics like to create return visits. I had bent my subframe hitting a manhole at night, idiot street repavers cut down the pavement to lay a new layer of asphalt down so the manhole was sticking up, no barricades around it, no street lights, raining…mercedes had it for 3 weeks due to mechanic shortage. Picked it up around 6pm, only the cashier was open for clients to pickup their cars after hours. Got about 2 miles down the road and started to hear a faint clicking sound when I step on the brakes, so I couldn’t turn around for service, rental car was already returned and they dropped me off at Mercedes. I had to drive about 50 miles to get home sound was getting worse, helicopter sound now, I exited the interstate, recalling what my GF said about the sound as she watched someones tire roll past her at night doing 40mph (hers).
pulled into a gas station and looked, I had only two lug bolts left, and both were loose on the left front, one was halfway out. I was just minutes away from loosing the wheel. I took bolts from two other wheels to get home