ChicagoPete

Hi,
New member here.

GL went into the dealer in early Dec... all 4(?) cooling lines to the turbos needed replacement.

That got fixed and picked up the car and had no heat. Said the desiccant bladder ruptured:

• Replaced coolant bottle
• Replaced heater pump
• Replaced thermostat
• Flushed entire system

Worked great for 3 weeks. Same issue returned. Minimal, luke warm heat.

And, I can literally see/watch the temp gauge fluctuate from 80-97, up and down while driving. Temp sensor bad?

Can the replacement coolant bottle with new desiccant bag rupture again?? How would I visually check if the bag is ruptured?

chassis

Air bubble? Do you have two coolant reservoirs - the main one and a second one in the engine vee?

Are you losing coolant elsewhere besides the turbo lines? e.g. water pump, cylinder head or out the tailpipe?

arsupisemnet

Temperature fluctuating because your thermostat opens up. How low it drops depends on your driving habits, but I can easily guess that you heavy on foot. Temperature drops to 80 by forced cooling during moderate heavy loads. There's a heater pin to keep thermostat open for that.
Check for air bubbles in heater system.

ChicagoPete

Appreciate the replies....

Honestly, in the old days I drove with a "heavy foot", not anymore. With the S8, hell yeah, wolf in sheep's clothes.

Been monkeying around with settings:

• Max defrost comes out nice and hot
• Max in the foot wells, solo comes out nice and hot
• When both of those are solo, blows cool air out of the rest
• Dash vents always blow cool or luke warm

Making me think the distribution thingy under the cowl is bad? I had one of those go bad in the S8, assuming there is the same in the GL?

I have not checked yet for air bubbles...
And, have not looked yet for a 2nd cooling tank.

chassis

Repeat the same test with engine warm and increase engine rpms as high as the ECU allows. See if HVAC performance is related to engine rpm.

ChicagoPete

Did not get to this test yet...

As far as I can tell, I only have a single coolant expansion tank.

Jumped in the car tonite and no fan blowing at all! On any setting. Dash says correct fan speeds, but, nothing.

Now this thing is completely undrivable here in the winter in Chicago.

I can 't really find any threads relative to this issue, except a YouTube video of a loose wire under the passenger floor mat. Before I start theorizing what it might be...

chassis

Read codes.

ChicagoPete

I will, but, forgive me for being ignorant... are these codes stored?

Jumped in the car this morning and everything was just fine and blowing warm.

chassis

Codes can be stored, yes.

kih

We are dealing with the same issue. Our heat stopped working. Cause is a burst Dessicant bag (Silica beads) in the coolant system. These beads go through the entire coolant system and clog everything. We were told we could try to flush the system - but that did not work. We are now being told we have to replace the entire cooling system - quote is $10,000. This is a $20 part that they place in the coolant to “preserve” the liquid to avoid replacing the fluid. I am trying to figure out if there is a way to make Mercedes accountable for the horrible design and make them help pay for the damages. My car, that is in otherwise perfect condition, is now trash due to these unnecessary silica beads. The dealer has been no help - and we’ve always only serviced the car through Mercedes’ and did all recommended services through the dealer.

ChicagoPete

Yep, spent all the $ at the dealer.

Find a reliable indy shop. Dealer did my coolant flush and like my original post, problem came back.

I did find a good indy shop and did a 2nd coolant flush(real flush, not just a drain and refill), WAY better results. I will do another(3rd flush) and perhaps a 4th as time passes.

The indy mechanic sent me pictures of all the crap the dealer missed. Unimaginable. But, considering the shortage of vehicles, turning and burning cars in and out of the service dept these days, seems routine.

Jamaal J

Not sure if you are still monitoring this post but which indy shop did the flush for you.

ChicagoPete

I use a guy right outside of the Glen in Glenview, my service manager from Autohaus on Edens gave me the referral.

Shoot me a PM and I'll send along his name and #.

FastBenzer

I had the same issue in my 2012 ML63. Low or no heat, intermittent fan force on defrost. It was indeed the desiccant and it fully blocked my heater core. I also had two directional control motors (there are eight under the top dash) that were jammed up. I had the whole system flushed, replaced the heater core and the two directional motors and now it is working perfect. Total cost was about $3000 because to replace the parts the entire dash has to come out (11 hours of work). The work included bleeding out any air in the system and a second flush. I still have to decide if I want to replace the desiccant bag. I am with others. Might be better just to replace the fluid from time to time. BTW, I cut open the old heater core and it was definitely crystals of desiccant inside. Now, it is back to fine motoring.

arifk

Where is the desiccant bag located on the GL450?