Brian you living in Durham have accsess to some good MB indy mechanics and tool/part stores.

Never charge without monitoring high side and low side pressures. The walmart 134a hose/can does not have a hose for high side. you do not want to overcharge.

What makes you think it needs anything if cooling? When you connect to the schrader valves you run the risk of introducing air/moisture into system.

Sight glass is supposed to be clear when engine is reving and slight bubbles when you first turn it on then goes to clear/cloudy.

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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification