Loosing coolant from the reservoir tank
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Newbie
Joined: May 2017
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W220
Loosing coolant from the reservoir tank
I am loosing coolant from the reservoir tank and the dash indication comes up every 3 day however no other leaks are evident it's 1999 W220. Please advice what I should look for, infact I tested a new tank and lid and the same friction as the present lid so appreciate some input please
Super Member
Joined: Jan 2015
Posts: 920
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From: Worcestershire UK
W124 260E
First easy one would be to replace the expansion tank cap . If the rubber seal on the base of the cap is split ,, or fine airline cracks ,then it will loose water down in to the outlet as the pressure builds up.Fill the tank up when its cold .
MBWorld Fanatic!
Joined: Dec 2012
Posts: 2,473
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From: Ball Ground, GA (N of Atlanta)
2003 S500 2007 GL450
As tusabes says, the firewall connector is a common leak area, and leakage here is difficult to detect.
The W220 has a double firewall between the engine compartment and the passenger compartment. Buried deep in the area between these firewalls are all of the HVAC (heater) coolant connections, as well as pumps and valves for that system.
One of those connectors is a black plastic tubing fitting (P/N 2208320015, about $10) that fits into a hole in the firewall that is closest to the engine, and connects to a heater hose on each side. It is common for this fitting to be under stress from the hoses and firewall, and the stress often results in a hard-to-see crack in the fitting. Replacement access is a little difficult, and you have to remove the wiper arms, but the job is well within the capabilities of most owners, and the fitting is cheap. You lose surprisingly little coolant during the replacement.
If you attempt this replacement, remember that the engine hood (bonnet) has button releases on the hinges that allow the hood to lock into a vertical position, improving access to the area.
A search on the W220 forums, and on the internet in general, using terms like "W220", "heater hose fitting", and "2208320015 " will find quite a bit of info. Do remember that this is only one possibility for your leak!
https://mbworld.org/forums/s-class-w...-firewall.html
http://www.benzworld.org/forums/w220...een-black.html
The W220 has a double firewall between the engine compartment and the passenger compartment. Buried deep in the area between these firewalls are all of the HVAC (heater) coolant connections, as well as pumps and valves for that system.
One of those connectors is a black plastic tubing fitting (P/N 2208320015, about $10) that fits into a hole in the firewall that is closest to the engine, and connects to a heater hose on each side. It is common for this fitting to be under stress from the hoses and firewall, and the stress often results in a hard-to-see crack in the fitting. Replacement access is a little difficult, and you have to remove the wiper arms, but the job is well within the capabilities of most owners, and the fitting is cheap. You lose surprisingly little coolant during the replacement.
If you attempt this replacement, remember that the engine hood (bonnet) has button releases on the hinges that allow the hood to lock into a vertical position, improving access to the area.
A search on the W220 forums, and on the internet in general, using terms like "W220", "heater hose fitting", and "2208320015 " will find quite a bit of info. Do remember that this is only one possibility for your leak!
https://mbworld.org/forums/s-class-w...-firewall.html
http://www.benzworld.org/forums/w220...een-black.html
