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Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 27813
Experience:  Over 15 years experience as a Mercedes dealer technician
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I have a 2013 GL450 the check coolant level message pops up,

Customer Question

I have a 2013 GL450 the check coolant level message pops up, car does not run hot runs at the exact temp level when new, I add coolant, not much the warning goes off, then I noticed a small pool of coolant on the ground, car still is at normal running temp, then the check coolant light comes back on.
Submitted: 1 year ago.
Category: Mercedes
Customer: replied 1 year ago.
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 1 year ago.
my phone number is(###) ###-####
Customer: replied 1 year ago.
Quick to pounce to make a sale, take my money and then not respond.
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.I apologize for any delay.I need a little more info to assist better.

Have you had the coolant system pressure tested to locate the coolant leak or inspected the engine for the coolant leak at all?

Let me know so we can continue,thanks Pete.

Customer: replied 1 year ago.
No pressure test. The coolant overflowed from the reserve coolant tank however the coolant warning stated coolant low and the vehicle coolant temperature is just above 80 , the normal operating temp of this vehicle since day one when new.
Expert:  Pete replied 1 year ago.

When you check the coolant level do you find it low in the reservoir to where you add coolant and when added the light turns off but then the coolant leaks out of the reservoir and the process starts over am I correct?

Customer: replied 1 year ago.
Example it overflowed yesterday, temp was normal, coolant check light was on, then the over flow stopped, light was still on. This morning low coolant light on, normal temp, no overflow, check the reserve tank had roughly a 1/2 inch of coolant.
Expert:  Pete replied 1 year ago.

O.k.,with coolant over flow like this here this is either caused by a coolant reservoir cap that isn't holding coolant pressure as it should hold up to 15 psi and it may be allowing coolant to flow past it out the over flow tube or there is an issue with a leaking cylinder head gasket that is leaking only exhaust gas and pressure past the gasket into the coolant system causing excess pressure into the coolant system causing the over flow.

With no over heat issue I suspect this may be the reservoir cap itself not holding pressure like it should with it needing replaced.

I would start with replacing the cap with the correct cap from a dealer for this model and if the pressure still pushes out I would have a block test done to test and see if exhaust is pushing into the coolant system with a head gasket leak (this won't show up as an external fluid leak or internal oil mixing with coolant) needing repaired.

Let me know if you need anything else here and feel free to rate my help.In some cases it can be difficult to fully diagnose your vehicle without seeing it so I do the best possible that I can from here.Thanks Pete

Customer: replied 1 year ago.
I do see residue underneath the reserve tank cap, looks like greenish build up and signs of dried up water marks.
Expert:  Pete replied 1 year ago.

With no other leaks and no over heat issues I suspect the cap isn't holding pressure needing replaced.I would have the coolant system pressure tested though to make sure no other components are leaking and no other coolant issues are present as well.

Thanks Pete