I'm working on the 1984 300DT. When pulling a new oil gauge pressure line through the fire wall, I accidentally loosened a black vacuum line. Under the hood, the line comes from the top of the injection pump and then travels through the firewall and connects somewhere. Does anyone have any
ideas where this black vacuum lines connects? Thanks!

It's just the vent line for the vacuum system. It goes into the cabin to source "clean" air.

You didn't knock it off of anything.

thanks, I'm going to connect the oil pressure gauge line to the instrument cluster, fill the sump and start it up.

Don't f-up............

Some how I kinda think he will know real quickly if he screws that up !

__________________
1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

I use a flare nut wrench to back up the oil gauge while tightening the
actual oil gauge line using a 10mm.....I learned my lesson the hard way (diesel oil soaked floor board, blue jeans and brand new boots...expensive lesson).

From memory (10 years ago), that line has a very small fitting and the torque required to seat the nut is very low. Do you really need a flare nut wrench on the gauge for it?

I use the flare nut wrench to hold the stationary bolt that is permanently attached to the back of the oil pressure gauge itself. This is so when I tighten the 10mm oil pressure gauge line (which goes into the oil gauge), I don't put too much force or tension on the action fitting. Last time I used only the 10mm wrench to simply tighten the oil gauge line, but must have used too much force which broke the weld and cause the oil gauge to leak a lot of oil.

then, I had to source an oil pressure gauge which required a lot of time and effort; I actually purchased a back up unit in case I make the same stupid mistake.

I suppose my question is whether the gauge actually needs so much torque to prevent any leakage from the fitting? These fittings have a tapered seat and seal with relatively low torque. The forces within the fitting itself are very high despite the low torque from the wrench.

OK, I understand.