Leaking diesel around the secondary filter 1984 300TD W123
 

I have some diesel fuel leaking around the secondary filter. It looks like it may be coming from the bolt on top that holds the filter on. I changed the filter last night to make sure it wasn't the gasket on the filter itself. How does that bolt work anyway? It seems to have a small metal washer on it but no gasket or o-ring at all. Is that normal? Also, there is a hole in the bolt on the side, does that need to line up with the hole in that block it bolts to?

Your 84 should be like my 85 set up. there should be 2 "O" rings on the shaft of the bolt. there doesn`t need to be a gasket between the bolt and filter housing.

Use a 22mm wrench/socket to loosen the bolt, then unscrew the filter, drop it down, and lift it out. be sure to fill the new filter before replacing it. saves a lit of headachs getting the engine to start. give the primer a few pumps also.

the bolt doesn`t need to be super tight, just firmed down. the alignment of the bolt shouldn`t matter.

the older style bolt and filter housing required an aluminium washer between the bolt and housing. It didn`t have the 2 "O" rings.

Charlie

I think I have the aluminum washer on mine. How do I keep it from leaking? I got it pretty tight without over cranking it.

You might need a new washer, the old one probably has been on and off a few times. maybe try turning it over.

If you do try that, look on the bolt to see if there are 2 rubber "O" rings. maybe they need to be replaced. If you have them, you don`t need the washer.

I went out to the shop and looks at an extra one I have, the part # is 615 092 02 08 F. actually have 3 and all have that "F" not sure if it is part of the #.
check and see what yours is.
Iam thinking if yours has the "O" rings and you are using the washer, maybe it lets the rings set too high and they don`t seat well.

Charlie

Unscrew the Filter Bolt enought that you can see if it has an upper O-ring groove.
Harbor Freight is now selling a Metric O-ring Store House kit and it looks like the large upper ring is the P14 O-ring that you get 10 of and the lower smaller O-ring is the P10a O-ring in the kit.
If your Filter Bolt no groove and uses the Washer there was a recent thread that ask the size and the answer was the Inside Diameter of the Washer is 18mm.
If you can find one Copper washers last longer and can be re-softened by heating them Red Hot.

^Agreed, if you have the two "o" rings, don't over tighten the filter, just snug it up without a bolt washer. I went through the same thing, couldn't figure it out for a while. The last time I changed filters, it just snugged it up, no leaks.

I'll pull the bolt out again this weekend and double check, but I'm fairly certain I have the washer only. I'll take a look at that other thread about the copper washer. I've attached a photo. It seems like I may be getting some leakage from that smaller bolt towards the front of the housing as well. Is it the same story there with the washers?

you don't have o-rings, change the washer. I'd get a new aluminum one, the copper ones will work also, but dissimilar metal corrosion on the aluminum case would concern me.
the smaller bolt has two washers one under the bolt head, and one under the banjo fitting itself.

In the past the Bosch Fuel Injection Pump rebuild kits came with a bunch of Copper Washers. Including Copper Washers where the Fuel Inlet Banjo Bolts and the Over Flow Valve bolt up to the Aluminum housing.
Since that time in the late 1970s the price of Copper has risen and you now see Aluminum Washers.

You also might check to be sure that the return fuel line/hose (the smaller ones) are not leaking.

They could be leaking fuel down around those bolt heads making it appear that the fuel is coming from the bolt housing/opening when it is not.

Just something else to look for/at. I know what it's like to chase ghosts.

I'll be taking a hard look at it this weekend. For those washers, is it best to just take it all apart and take the loose washers to the parts and/or hardware store looking for new ones?

I believe the washer is a 19mm, I.D.

I've been trying to pinpoint the leak. I found a crush washer that is the right size for the 17mm bolt on the top of the housing. What is that smaller braided hose for? It seems to be leaking from both ends. Does it go to the injectors? I'm still learning where everything is in the engine.

On your 84, you have the 'old' setup.

The only way I could fix my leak on the '82 was to find a 'new' filter setup in a junkyard and swap it in (with new o-rings). I tried everything too...the mating surface was just too marred over time.

The new setup has a 24 mm top bolt. The old one was 22 or 21 mm (the one you have).

X2. I would have thought the 84 had the newer style, maybe some PO changed it to the older style.

one from the JY couldn`t cost more than $10 or so. look for the part# I listed in post #4. or pull the bolt and see if it has 2 "O" rings.

I changed the one in the 80 240 to the newer style when I got it to make life simpler.

Charlie