Hi,

I have an '87 190d Turbo 2.5 and am in the process of replacing the o-ring on my fuel thermostat. I noticed a constant drip originating from the fuel thermostat while I was replacing the inline fuel filter and have been attempting to replace the o-ring. I ordered the o-ring from the dealer and just got it today but right now I'm having trouble figuring out where the o-ring goes. I never found the old one.

Does the o-ring go on the actual plastic nipple held on by the circlip? Or do you have to place it inside the fuel thermostat before putting the plastic part and circlip back on? Any help is greatly appreciated.

Ok, I took another look at the plastic part and after cleaning it up a bit more it looks like there is an p-ring on it. I took it off to put the new o-ring on but the new one is shaped more like a donut where as the older one was flatter and fit better. The part the dealer gave me is 011-997-39-48. Maybe they gave me the wrong part.