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Old 01-18-2003, 11:30 AM
Senior Member
Join Date: Sep 2002
Posts: 2,484
Hey guys, I think I can shed some light on the gurgling noise. In 1991 MB came up with a temporary cure for this. We were instructed to raise the front of the vehicle so that the expansion tank was the highest point in the cooling system (except for the top of the radiator). With the pressure cap removed and the climate control set to maximum heat, run the engine at 2500 RPM for at least five minutes. This allows the air trapped in the heater core to escape. I did it several times and it worked just fine. A short time later MB made available an air separator that was to be installed at the area of the heater hose near the firewall on the drivers' side. It was a very straightforward job that is easily within the ability of most DIYers. It's been at least ten years since I've done this job so I'm probably missing a few details, but I'll check it out Monday morning when I get to work. As far as the auxiliary water pump being the reason for the air in the system, I've never heard of that before, but anything is possible.
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