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

2014 GL450 coolant /flush change and intercooler

Old 02-22-2019, 02:54 AM
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1996 S320, 2007 GL450, 2014 GL450, 2015 GL450
2014 GL450 coolant /flush change and intercooler

Hi all,
Recently updated from a 2007 to a 2014 GL450. Flushing the cooling system I should be able to figure out but would appreciate any tips and tricks you may have. After removing the engine covers I see an extra coolant tank, this is where I need to be educated. What is it for? How do I drain that system? Does it use the same anti-freeze the engine uses.
Thank You
Mike
Old 02-24-2019, 10:30 AM
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2015 GL 550
I just took our 2015 GL550 in for its "fourth birthday" service and they diagnosed a coolant leak involving something that sounds like what you described. It required a part that had to be shipped from Germany, it took over a week to get here ... has Mercedes-Benz heard about FedEx ... but it was all covered under warranty and we had the use of a GLC loaner. If you have an extended warranty on your 2014 GL550 your repairs may also be warranted.

If not ... be prepared. Judging by all the "line items" on the service report there is a lot of work involved. If all you are doing is flushing the system and not repairing the system you're good!
Old 02-24-2019, 11:01 AM
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2009 E550, 2011 GL550, 2013 GL550
Last time I checked, the "extra coolant tank" was for the turbo cooling.
Old 02-26-2019, 04:14 PM
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We were getting "Coolant Low" warning messages ... especially on cold winter mornings, but our dealership diagnosed it the 'intercooler' system for the turbos. Required a part from Germany and two weeks to resolve!
Old 11-19-2022, 01:00 PM
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2014 GL450
@hammyj , have you figured out how to flush the turbo coolant reservoir? (i.e. the extra reservoir under engine cover)? I need to figure this out.

Thank you very much!


Originally Posted by hammyj
Hi all,
Recently updated from a 2007 to a 2014 GL450. Flushing the cooling system I should be able to figure out but would appreciate any tips and tricks you may have. After removing the engine covers I see an extra coolant tank, this is where I need to be educated. What is it for? How do I drain that system? Does it use the same anti-freeze the engine uses.
Thank You
Mike
Old 11-21-2022, 04:13 PM
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1996 S320, 2007 GL450, 2014 GL450, 2015 GL450
Hi deeperblue.
Since many manufactures no longer supply drain plugs on cooling systems, including the turbo coolant, to save $1.00 per vehicle I have found only one choice to achieve this. Follow the hoses associated with the system you want to flush / drain. Find the lowest hose connections and carefully remove the hose(s) to drain the system. If you have compressed air available use about 5 - 10 lbs of air from the highest hose connection or the reservoir to force the coolant out. Use tap water (garden hose) and flush from the top down, than use air again. Assuming the water is clean now, and all drained, connect all hoses. Refill with the correct coolant, run engine without the reservoir cap installed, the coolant will go down in the reservoir as air is removed from the system. Feel the different hoses to make sure they are all about the same temperature. (checking circulation). Once the system seems to have stabilized install the reservoir cap. Check the reservoir after driving and cooled down several times. Mine has been stable since I performed the flush.
Old 11-23-2022, 12:38 PM
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2014 GL450
Thanks!

Originally Posted by hammyj
Hi deeperblue.
Since many manufactures no longer supply drain plugs on cooling systems, including the turbo coolant, to save $1.00 per vehicle I have found only one choice to achieve this. Follow the hoses associated with the system you want to flush / drain. Find the lowest hose connections and carefully remove the hose(s) to drain the system. If you have compressed air available use about 5 - 10 lbs of air from the highest hose connection or the reservoir to force the coolant out. Use tap water (garden hose) and flush from the top down, than use air again. Assuming the water is clean now, and all drained, connect all hoses. Refill with the correct coolant, run engine without the reservoir cap installed, the coolant will go down in the reservoir as air is removed from the system. Feel the different hoses to make sure they are all about the same temperature. (checking circulation). Once the system seems to have stabilized install the reservoir cap. Check the reservoir after driving and cooled down several times. Mine has been stable since I performed the flush.

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