C218 CLS63, 2011 - 2019

W218 CLS63S - coolant issue

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Old Mar 1, 2024 | 08:01 AM
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CLS 63 S AMG 4 MATIC
Unhappy W218 CLS63S - coolant issue

Hi Guys,

SO recently iv encountered a problem with the coolant system on my car, below is a brief history of what has happened.
  • I was driving on sports + and the coolant system had exploded so i pulled over and turned the car off immediately.
  • The garage ive been taking it to for over 4 years diagnosed the problem as a leaking reservoir and leaking coolant hose which they replaced.
  • I then received the car but this is where the problem arises.
  • When running the car and the engine gets to temp the coolant goes all the way down triggering the check coolant warning.
  • I then slowly turn the reservoir cap which then cause the coolant to come rushing back up to the point of initial filling.
Ive read that these reservoirs are self bleeding, the garage said it cant be any issues with head gasket failure as they completed a pressure check on coolant system .

Any advice would be really appreciative as i love the car and i've driven almost 130,000km on it taking great care.
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Last edited by cls63sdxb; Mar 1, 2024 at 08:52 AM.
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Old Jun 18, 2025 | 06:00 PM
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CLS63AMG
Hi, please, I have a similar problem. How did you remove it, solve it
Thank you for your time
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Old Jul 28, 2025 | 02:53 PM
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W212 MY'14 M276-3.5NA @75kMi
IMPROPER FILL PROCEDURE

coolant goes away then comes back up.... there is an air pocket in your cooling system: engine or radiator.
Use the vacuum refill method.

RTFM : do not open system at operating temperature... 200F degree burning hazard!

Last edited by CaliBenzDriver; Jul 28, 2025 at 02:55 PM.
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