Originally Posted by DAVECAD2.0

Just thought I'd throw this in. Was chasing a leak in my '91 420 SEL. Thought it was the dreaded expansion valve as there was green dye on the lower hose ends, and the carpet, and lower dash cover. Replaced the expansion valve (not really that bad) had the system juiced up. Found dye on the small lower expansion valve hose. Turned out the hose from the filter/drier to the expansion valve had two tiny pin hole leaks on the rubber part from the false firewall into the cabin. Since it runs down hill it collected right at the metal fitting at the EV. Anyway if you think the expansion valve is leaking, you might want to check the hoses first.