GL Class (X166) 2013-2015 after facelift became GLS (X166)

GL550 cooling system leaks

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Old Dec 6, 2022 | 04:22 PM
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Question GL550 cooling system leaks

2015 GL550 seems to have an inherent problem with coolant seeping out around each coolant reservoir cap. I have had the car in to the dealer a couple of times for this and they say they can't find anything wrong, even after showing them the residue around each cap. Once they just cleaned off the residue and sent me on my way. The second time I made them replace the caps, or so they said they did, with no difference. About every 10,000 miles I get the check coolant waring light. Upon inspection, both tanks are slightly down and there is a lot of coolant residue around each cap. They have pressurized the system twice with no coolant loss, but they won't address the residue. Any others having this issue or see coolant residue around the tank caps?

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Last edited by zeroroadkill; Dec 6, 2022 at 04:24 PM.
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Old Dec 6, 2022 | 07:13 PM
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Do you have a failed head gasket or other internal coolant leak which causes the coolant consumption?

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Old Dec 7, 2022 | 08:03 AM
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That is normal process. No one stopped evaporation and pressure increase due to thermal processes
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Old Dec 7, 2022 | 10:50 AM
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Originally Posted by chassis
Do you have a failed head gasket or other internal coolant leak which causes the coolant consumption?
No.
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Old Dec 7, 2022 | 10:53 AM
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What?
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Old Dec 7, 2022 | 10:54 AM
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Question

Originally Posted by arsupisemnet
That is normal process. No one stopped evaporation and pressure increase due to thermal processes
What???
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Old Dec 7, 2022 | 11:19 AM
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Your engine goes hot - some of the pressure realeses through reservoir cap consisting of coolant vapor. That is what you see...
To make sure your gasket is not blown go and do exhaust gas in coolant test - you can Google it...
overwise nothing to worry about.
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Old Dec 14, 2022 | 10:45 PM
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Our garage has always smelled of burnt coolant. It has been in to have some of the plastic tubes replaced. The reservoir has puked coolant on the floor. I try to carefully keep it at the right level.
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Old Dec 15, 2022 | 02:30 PM
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Yeah, I smell coolant all the time after parking the car in the garage. I've had the caps replaced twice and the plastic "Y" connectors that run coolant to the turbo's replaced. They can crack.
I just pulled both caps, cleaned off the residue and securely tightened them back on.

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Old Dec 15, 2022 | 08:48 PM
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Originally Posted by zeroroadkill
Yeah, I smell coolant all the time after parking the car in the garage. I've had the caps replaced twice and the plastic "Y" connectors that run coolant to the turbo's replaced. They can crack.
I just pulled both caps, cleaned off the residue and securely tightened them back on.
That doesn't look like a leak. MB coolant systems ooze or sweat coolant in various places. One is the reservoir cap, another is the circulation pump, an electric coolant pump installed behind the left/driver's-side headlamp.
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Old Dec 16, 2022 | 06:26 PM
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Originally Posted by chassis
That doesn't look like a leak. MB coolant systems ooze or sweat coolant in various places. One is the reservoir cap, another is the circulation pump, an electric coolant pump installed behind the left/driver's-side headlamp.
Yeah I know that, the pump always smells but no sign of any leaks or residue. Both reservoir caps have coolant dried residue around them, not the first time I have cleaned them. Usually there is a problem with the plastic "Y" tube that goes to the turbos, but I have had that replaced when they had the engine out. They actually cracked it putting the engine back in!
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