tips on changing fuel filter?
 

Changed the fuel filter in the 300D today what a mess! Got any tips on not spilling any fuel? My first mistake was doing it on an incline with nose down instead of facing the other way. Second was I just filled the tank. I had to loosen the return banjo bolt to get to the center nut. When the banjo was removed, fuel runs out of there at a pretty good rate. After the big filter center bolt was removed, fuel gushes out of there at an even higher rate. I tried to work fast and thread the new filter in but had a lot of trouble getted the thread started (imo, no need for such tight thread tolerance there). I must have lost a gallon.:(. I guess I should have pinched the supply and return hoses before I started huh? Anyone replace the Mercedes fuel filter head with an aftermarket unit? I am seriously considering doing that.

Don't do either of these things and it won't leak a drop.

X2.

And, make sure the filter is filled to the brim before you secure it with the bolt.

I kinda knew it was going to leak but not that much. I was lazy and didn't feel like turning the car around. Live and learn, :rolleyes:

Use a clamp on the hose from the metal fuel line to the primary filter to keep fuel from running out of the tank. I bought little clamps made specifically for this purpose (and very cleverly called "hose clamps") but just about anything will work – I have used vice-grips (carefully!) in the past.

Brian has the best idea so far for filling the new secondary filter: fill the filter about 3/4 full with clean diesel fuel and then get it into place. Now use a tool – hose, funnel, whatever – to fill the filter all the way full and put in the bolt to hold it. That way you don't spill from a full filter trying to wiggle it into place.

Jeremy

I changed both filters today, it was easy & painless. I just loosened the bolt on top with a crescent wrench, unscrewed the primary filter, filled the new one with ATF ("benz abuse") and screwed it on, tightened the bolt. Then I changed the secondary. Then when I took the car to the carwash I cleaned up the diesel I always spill on the motor mount.

Also my mechanic said the top bolt breaks about 1/3 the time he changes filters for some reason.

Hmm.........let me guess...........he tightens it to 150 lb.-ft.:rolleyes:

What size wrench is that bolt? Mine is pretty big. I think about 27 mm. A socket or box end won't fit. Neither will an open end because the wrench is too thick. Also, where can I get those aluminum washers (on the banjo bolt) locally?

If so, you'd be in a heap of trouble using that pipe wrench............;)

On the main filter I use my vacuum oil extractor to remove fuel from filter before the tilt to remove. I put the new filter back in place and fill it through the bolt hole to the brim and then tighten.

O ring seal
 

Did you open the tank to relieve the pressure?? Open the cap and you will find that it has pressure in the tank(at least the three Mercedes I have keep pressure in the tanks). Until the pressure is gone it will spew fuel all over the place. (ask me how I know)
The bolt does not require much torque to seal the filter it is the O ring on it that will not seal and people tighten the ____ out of it in a effort to stop the leak. Get a new O ring every other filter change and it will be no trouble. Treat the filter like a oil filter - lube the rubber ring on the can and when it touches the housing then about 3/4 turn more.

Robert

Just to avoid people from being misled by terminology, I believe you have the names of the filters reversed. Primary is the plastic one, secondary is the 'spin on' type.

Due to the vent, there should be no pressure or vacuum in the tank, unless the vent is blocked.

That bolt needs either a 24 or 27 mm wrench. That's a big bolt! I wouldn't let that mechanic who breaks it 1/3 of the time anywhere near my car. :D

Vent
 

Are you sure?? I have three of them 84 300sd, 85 300sd, and 84 300cd and they all keep pressure in the tank even for days. There is a check valve on the side of the tank but I thought that it was to keep from having a vacuum. It is aggravating at times when the pressure will bust a return line and leak for several days if the tank is half full.

Where is the little sucker and how do I fix it??

Thanks for pointing that out I thought that they were like that.
Robert