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Super mechanic
Super mechanic, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 16839
Experience:  ASE Master, 30+ years exp. troubleshooting, diag. electrical, collision
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Mercedes S420: some problems with the heating pipe and it overheat

Customer Question

my mercedes S420 has some problems with the heating pipe and it overheat. Can you please help?
Submitted: 6 years ago.
Category: Mercedes
Expert:  Super mechanic replied 6 years ago.

Hello and welcome to Just, Super mechanic here. About your vehicle.

Does it over heat at all speeds?

Cooling system full?

Pipe leaks? Does it have heat?

Customer: replied 6 years ago.

yes it overheats at all speeds


i did not check the cooling system but I will check later


the pipe leaks and the car has heat.


This pipe is broken and the antifreeze comes out extensively when the car is on.

Expert:  Super mechanic replied 6 years ago.
You will want to stop any leaks so that the system can operate properly, also make sure that it's full of coolant/water mixture.


The first thing that you want to do is check the cooling system for any exhaust gases. There is a tester for that, that you can gt from Autozone for about $20. It comes with instructions, but there is a blue fluid that is used in it, if the fluid turns yellow, that is exhaust gases.

Block tester available as:

Snap-On GDCT16


If there are any exhaust gases in the cooling system, that will cause more pressure than desired and will allow the engine to burn coolant and/or heat the coolant up too high.

If there are, then there would be an internal engine problem, like a head gasket or head.